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C# How To Initialize a generic Class with a type variable

disclaimer I'm a newbie in understanding Reflection.
abstract class BaseClass<T>
{
public abstract T Value { get; }
public virtual bool CheckValue(string input)
{
return true;
}
}
class NotBaseClassA : BaseClass<string>
{
public override string Value { get => "Yes";}
public override bool CheckValue(string input)
{
return 1 == 2;
}
}
class NotBaseClassB : BaseClass<int>
{
public override int Value { get => 1; }
}
class ManyBaseClasses
{
public NotBaseClassB notBaseClassB;
public NotBaseClassA notBaseClassA;
}
class Programm
{
public void Main()
{
foreach (PropertyInfo pi in typeof(ManyBaseClasses).GetProperties())
{
string input = Console.ReadLine();
//Get the generic type of the propertyInfo
//BaseClass<type> bt = new BaseClass<type>();
//Instantiate BaseClass not as a var So I can do
//BaseClass.CheckValue(input)
}
}
}
I'm just trying to do like the title says. So i saw this answer but the answer returns a 'var' but I cant call my CheckValue() function from a type var. (Or i dont think I can?). What i Need is to Instantiate my BaseClass<> with the correct type from a type variable and not as a var, as a proper BaseClass obj so i can then call my functions.
Edit 1 : i've already managed to get the generic type in the variable by doing something like that
public static System.Type GetBaseClassType(this System.Type type)
{
System.Type[] types = new System.Type[]{ };
while (type != null && type != typeof(object) || types.Length == 0)
{
types = type.GetGenericArguments();
if (types.Length > 0)
{
return types[0];
}
type = type.BaseType;
}
return null;
}

The base class is not relevant in this case, as it's abstract, so you actually want to instantiate the derived class.
All you need to do to create it is
Activator.CreateInstance(pi.PropertyType)
Then you will need to use reflection on that result to call CheckValue, because there is no common base type or interface.
It might be easier to extract the non-generic code into a BaseBaseClass which is not generic, which means you don't need reflection for the second step.
abstract class BaseBaseClass
{
public virtual bool CheckValue(string input)
{
return true;
}
}
abstract class BaseClass<T> : BaseBaseClass
{
public abstract T Value { get; }
}
Then you can just do
((BaseBaseClass) Activator.CreateInstance(pi.PropertyType)).CheckValue(someInput)

I've done that before, but it was a long time ago. You have to create instance via reflection and call the method via reflection.
foreach (PropertyInfo pi in typeof(ManyBaseClasses).GetProperties())
{
string input = Console.ReadLine();
//Get the generic type of the propertyInfo
var propType = pi.Type;
Type[] typeArgs = { propType };
var genType = d1.MakeGenericType(typeArgs);
//BaseClass<type> bt = new BaseClass<type>();
object bt = Activator.CreateInstance(genType);
//Instantiate BaseClass not as a var So I can do
//BaseClass.CheckValue(input)
MethodInfo method = typeof(bt).GetMethod("CheckValue"));
method.Invoke(bt, new[] { input });
}

Compare if type is IEnumerable using generics [duplicate]

Using reflection, I'm attempting to find the set of types which inherit from a given base class. It didn't take long to figure out for simple types, but I'm stumped when it comes to generics.
For this piece of code, the first IsAssignableFrom returns true, but the second returns false. And yet, the final assignment compiles just fine.
class class1 { }
class class2 : class1 { }
class generic1<T> { }
class generic2<T> : generic1<T> { }
class Program
{
static void Main(string[] args)
{
Type c1 = typeof(class1);
Type c2 = typeof(class2);
Console.WriteLine("c1.IsAssignableFrom(c2): {0}", c1.IsAssignableFrom(c2));
Type g1 = typeof(generic1<>);
Type g2 = typeof(generic2<>);
Console.WriteLine("g1.IsAssignableFrom(g2): {0}", g1.IsAssignableFrom(g2));
generic1<class1> cc = new generic2<class1>();
}
}
So how do I determine at run time whether one generic type definition is derived from another?

From the answer to another question:
public static bool IsAssignableToGenericType(Type givenType, Type genericType)
{
var interfaceTypes = givenType.GetInterfaces();
foreach (var it in interfaceTypes)
{
if (it.IsGenericType && it.GetGenericTypeDefinition() == genericType)
return true;
}
if (givenType.IsGenericType && givenType.GetGenericTypeDefinition() == genericType)
return true;
Type baseType = givenType.BaseType;
if (baseType == null) return false;
return IsAssignableToGenericType(baseType, genericType);
}

The exact code you posted does not return surprising results.
This says "false":
Type g1 = typeof(generic1<>);
Type g2 = typeof(generic2<>);
Console.WriteLine("g1.IsAssignableFrom(g2): {0}", g1.IsAssignableFrom(g2));
This says "true":
Type g1 = typeof(generic1<class1>);
Type g2 = typeof(generic2<class1>);
Console.WriteLine("g1.IsAssignableFrom(g2): {0}", g1.IsAssignableFrom(g2));
The difference is that open generic types cannot have instances, so one is not "assignable" to the other.
From the docs:
Returns true if c and the current
Type represent the same type, or if
the current Type is in the
inheritance hierarchy of c, or if
the current Type is an interface
that c implements, or if c is a
generic type parameter and the current
Type represents one of the
constraints of c. false if none of
these conditions are true, or if c
is null.
In this case, clearly none of these conditions are true. And there's an extra note:
A generic type definition is not
assignable from a closed constructed
type. That is, you cannot assign the
closed constructed type
MyGenericList<int> (MyGenericList(Of Integer) in Visual Basic) to a
variable of type MyGenericList<T>.

In the following case use the method Konrad Rudolph provided could be wrong, like: IsAssignableToGenericType(typeof(A), typeof(A<>));// return false
I think here's a better answer
public static bool IsAssignableFrom(Type extendType, Type baseType)
{
while (!baseType.IsAssignableFrom(extendType))
{
if (extendType.Equals(typeof(object)))
{
return false;
}
if (extendType.IsGenericType && !extendType.IsGenericTypeDefinition)
{
extendType = extendType.GetGenericTypeDefinition();
}
else
{
extendType = extendType.BaseType;
}
}
return true;
}
the test case, see Using IsAssignableFrom with C# generics for detail
using System;
/**
* Sam Sha - yCoder.com
*
* */
namespace Test2
{
class MainClass
{
public static void Main (string[] args)
{
string a = "ycoder";
Console.WriteLine(a is object);
A aa = new A();
//Console.WriteLine(aa is A<>);//con't write code like this
typeof(A<>).IsAssignableFrom(aa.GetType());//return false
Trace(typeof(object).IsAssignableFrom(typeof(string)));//true
Trace(typeof(A<>).IsAssignableFrom(typeof(A)));//false
AAA aaa = new AAA();
Trace("Use IsTypeOf:");
Trace(IsTypeOf(aaa, typeof(A<>)));
Trace(IsTypeOf(aaa, typeof(AA)));
Trace(IsTypeOf(aaa, typeof(AAA<>)));
Trace("Use IsAssignableFrom from stackoverflow - not right:");
Trace(IsAssignableFrom(typeof(A), typeof(A<>))); // error
Trace(IsAssignableFrom(typeof(AA), typeof(A<>)));
Trace(IsAssignableFrom(typeof(AAA), typeof(A<>)));
Trace("Use IsAssignableToGenericType:");
Trace(IsAssignableToGenericType(typeof(A), typeof(A<>)));
Trace(IsAssignableToGenericType(typeof(AA), typeof(A<>)));
Trace(IsAssignableToGenericType(typeof(AAA), typeof(A<>)));
}
static void Trace(object log){
Console.WriteLine(log);
}
public static bool IsTypeOf(Object o, Type baseType)
{
if (o == null || baseType == null)
{
return false;
}
bool result = baseType.IsInstanceOfType(o);
if (result)
{
return result;
}
return IsAssignableFrom(o.GetType(), baseType);
}
public static bool IsAssignableFrom(Type extendType, Type baseType)
{
while (!baseType.IsAssignableFrom(extendType))
{
if (extendType.Equals(typeof(object)))
{
return false;
}
if (extendType.IsGenericType && !extendType.IsGenericTypeDefinition)
{
extendType = extendType.GetGenericTypeDefinition();
}
else
{
extendType = extendType.BaseType;
}
}
return true;
}
//from stackoverflow - not good enough
public static bool IsAssignableToGenericType(Type givenType, Type genericType) {
var interfaceTypes = givenType.GetInterfaces();
foreach (var it in interfaceTypes)
if (it.IsGenericType)
if (it.GetGenericTypeDefinition() == genericType) return true;
Type baseType = givenType.BaseType;
if (baseType == null) return false;
return baseType.IsGenericType &&
baseType.GetGenericTypeDefinition() == genericType ||
IsAssignableToGenericType(baseType, genericType);
}
}
class A{}
class AA : A{}
class AAA : AA{}
}

I have a different Approach that resolves this issue, Here are my classes
public class Signal<T>{
protected string Id {get; set;} //This must be here, I use a property because MemberInfo is returned in an array via GetMember() reflection function
//Some Data and Logic And stuff that involves T
}
public class OnClick : Signal<string>{}
Now if I have an instance of type OnClick but I dont know that, and I want to find out if I have an instance of anything which inherits from Signal<> of any type? I do this
Type type = GetTypeWhomISuspectMightBeAGenericSignal();
PropertyInfo secretProperty = type.GetProperty("Id", BindingFlags.NonPublic | BindingFlags.Instance);
Type SpecificGenericType = secretProperty.DeclaringType; //This is the trick
bool IsMyTypeInheriting = SpecificGenericType.IsGenericType && SpecificGenericType.GetGenericTypeDefinition() == typeof(Signal<>); //This way we are getting the genericTypeDefinition and comparing it to any other genericTypeDefinition of the same argument length.
So this works for me, its not recursive, and it uses a trick via a designated property. It has limitations that its hard to write a function that checks assignability for all generics ever. But for a specific type it works
Obviously you need to check if() conditions better and stuff, but these are the Raw lines required to evaluate assignability of a type to its base generic, this way.
Hope this helps

My two cents. IMHO it doesn't make much sense to separate implements, derives or the original functionality of IsAssignableFrom,
Constructing from the answers previously given, this is how I do it:
public static bool ImplementsOrDerives(this Type #this, Type from)
{
if(from is null)
{
return false;
}
else if(!from.IsGenericType)
{
return from.IsAssignableFrom(#this);
}
else if(!from.IsGenericTypeDefinition)
{
return from.IsAssignableFrom(#this);
}
else if(from.IsInterface)
{
foreach(Type #interface in #this.GetInterfaces())
{
if(#interface.IsGenericType && #interface.GetGenericTypeDefinition() == from)
{
return true;
}
}
}
if(#this.IsGenericType && #this.GetGenericTypeDefinition() == from)
{
return true;
}
return #this.BaseType?.ImplementsOrDerives(from) ?? false;
}

You need to compare the contained type. See: How to get the type of T from a member of a generic class or method?
In other words, I think you need to check whether the type being contained by the generic class is assignable rather than the generic class itself.

#konrad_ruldolph's answer is mostly correct, but it requires you to know the base type/interface is an open generic. I propose an improvement that combines a non-generic test with a loop to test for generic match.
public static class Ext
{
public static bool IsAssignableToGeneric(
this Type assignableFrom,
Type assignableTo)
{
bool IsType(Type comparand)
=> assignableTo.IsAssignableFrom(comparand)
|| (comparand.IsGenericType
&& comparand.GetGenericTypeDefinition() == assignableTo);
while (assignableFrom != null)
{
if (IsType(assignableFrom)
|| assignableFrom
.GetInterfaces()
.Any(IsType))
{
return true;
}
assignableFrom = assignableFrom.BaseType;
}
return false;
}
}

Creating an extension method and using link you can do this :
public static bool IsAssignableFromGenericInterface(this Type type, Type genericInterface) => type.GetInterfaces().Any(#interface => #interface.IsAssignableFrom(genericInterface));

I also would like to share my code with you. Here the generic arguments are checked for any compatibility and is working with interfaces.
public static bool IsAssignableToGeneric(this Type sourceType, Type targetType)
{
bool IsAssignable(Type comperand)
{
if (comperand.IsAssignableTo(targetType))
return true;
if (comperand.IsGenericType && targetType.IsGenericType && comperand.GetGenericTypeDefinition() == targetType.GetGenericTypeDefinition())
{
for (int i = 0; i < targetType.GenericTypeArguments.Length; i++)
{
Type comperandArgument = comperand.GenericTypeArguments[i];
Type targetArgument = targetType.GenericTypeArguments[i];
// suggestion for improvement: forward the type check recursivley also here
if (!comperandArgument.IsGenericTypeParameter && !targetArgument.IsGenericTypeParameter && !comperandArgument.IsAssignableTo(targetArgument))
return false;
}
return true;
}
return false;
}
if (IsAssignable(sourceType))
return true;
if (targetType.IsInterface && sourceType.GetInterfaces().Any(IsAssignable))
return true;
return false;
}

How to use 'is' operator with a generic class [duplicate]

I have a generic class in my project with derived classes.
public class GenericClass<T> : GenericInterface<T>
{
}
public class Test : GenericClass<SomeType>
{
}
Is there any way to find out if a Type object is derived from GenericClass?
t.IsSubclassOf(typeof(GenericClass<>))
does not work.

Try this code
static bool IsSubclassOfRawGeneric(Type generic, Type toCheck) {
while (toCheck != null && toCheck != typeof(object)) {
var cur = toCheck.IsGenericType ? toCheck.GetGenericTypeDefinition() : toCheck;
if (generic == cur) {
return true;
}
toCheck = toCheck.BaseType;
}
return false;
}

(Reposted due to a massive rewrite)
JaredPar's code answer is fantastic, but I have a tip that would make it unnecessary if your generic types are not based on value type parameters. I was hung up on why the "is" operator would not work, so I have also documented the results of my experimentation for future reference. Please enhance this answer to further enhance its clarity.
TIP:
If you make certain that your GenericClass implementation inherits from an abstract non-generic base class such as GenericClassBase, you could ask the same question without any trouble at all like this:
typeof(Test).IsSubclassOf(typeof(GenericClassBase))
IsSubclassOf()
My testing indicates that IsSubclassOf() does not work on parameterless generic types such as
typeof(GenericClass<>)
whereas it will work with
typeof(GenericClass<SomeType>)
Therefore the following code will work for any derivation of GenericClass<>, assuming you are willing to test based on SomeType:
typeof(Test).IsSubclassOf(typeof(GenericClass<SomeType>))
The only time I can imagine that you would want to test by GenericClass<> is in a plug-in framework scenario.
Thoughts on the "is" operator
At design-time C# does not allow the use of parameterless generics because they are essentially not a complete CLR type at that point. Therefore, you must declare generic variables with parameters, and that is why the "is" operator is so powerful for working with objects. Incidentally, the "is" operator also can not evaluate parameterless generic types.
The "is" operator will test the entire inheritance chain, including interfaces.
So, given an instance of any object, the following method will do the trick:
bool IsTypeof<T>(object t)
{
return (t is T);
}
This is sort of redundant, but I figured I would go ahead and visualize it for everybody.
Given
var t = new Test();
The following lines of code would return true:
bool test1 = IsTypeof<GenericInterface<SomeType>>(t);
bool test2 = IsTypeof<GenericClass<SomeType>>(t);
bool test3 = IsTypeof<Test>(t);
On the other hand, if you want something specific to GenericClass, you could make it more specific, I suppose, like this:
bool IsTypeofGenericClass<SomeType>(object t)
{
return (t is GenericClass<SomeType>);
}
Then you would test like this:
bool test1 = IsTypeofGenericClass<SomeType>(t);

I worked through some of these samples and found they were lacking in some cases. This version works with all kinds of generics: types, interfaces and type definitions thereof.
public static bool InheritsOrImplements(this Type child, Type parent)
{
parent = ResolveGenericTypeDefinition(parent);
var currentChild = child.IsGenericType
? child.GetGenericTypeDefinition()
: child;
while (currentChild != typeof (object))
{
if (parent == currentChild || HasAnyInterfaces(parent, currentChild))
return true;
currentChild = currentChild.BaseType != null
&& currentChild.BaseType.IsGenericType
? currentChild.BaseType.GetGenericTypeDefinition()
: currentChild.BaseType;
if (currentChild == null)
return false;
}
return false;
}
private static bool HasAnyInterfaces(Type parent, Type child)
{
return child.GetInterfaces()
.Any(childInterface =>
{
var currentInterface = childInterface.IsGenericType
? childInterface.GetGenericTypeDefinition()
: childInterface;
return currentInterface == parent;
});
}
private static Type ResolveGenericTypeDefinition(Type parent)
{
var shouldUseGenericType = true;
if (parent.IsGenericType && parent.GetGenericTypeDefinition() != parent)
shouldUseGenericType = false;
if (parent.IsGenericType && shouldUseGenericType)
parent = parent.GetGenericTypeDefinition();
return parent;
}
Here are the unit tests also:
protected interface IFooInterface
{
}
protected interface IGenericFooInterface<T>
{
}
protected class FooBase
{
}
protected class FooImplementor
: FooBase, IFooInterface
{
}
protected class GenericFooBase
: FooImplementor, IGenericFooInterface<object>
{
}
protected class GenericFooImplementor<T>
: FooImplementor, IGenericFooInterface<T>
{
}
[Test]
public void Should_inherit_or_implement_non_generic_interface()
{
Assert.That(typeof(FooImplementor)
.InheritsOrImplements(typeof(IFooInterface)), Is.True);
}
[Test]
public void Should_inherit_or_implement_generic_interface()
{
Assert.That(typeof(GenericFooBase)
.InheritsOrImplements(typeof(IGenericFooInterface<>)), Is.True);
}
[Test]
public void Should_inherit_or_implement_generic_interface_by_generic_subclass()
{
Assert.That(typeof(GenericFooImplementor<>)
.InheritsOrImplements(typeof(IGenericFooInterface<>)), Is.True);
}
[Test]
public void Should_inherit_or_implement_generic_interface_by_generic_subclass_not_caring_about_generic_type_parameter()
{
Assert.That(new GenericFooImplementor<string>().GetType()
.InheritsOrImplements(typeof(IGenericFooInterface<>)), Is.True);
}
[Test]
public void Should_not_inherit_or_implement_generic_interface_by_generic_subclass_not_caring_about_generic_type_parameter()
{
Assert.That(new GenericFooImplementor<string>().GetType()
.InheritsOrImplements(typeof(IGenericFooInterface<int>)), Is.False);
}
[Test]
public void Should_inherit_or_implement_non_generic_class()
{
Assert.That(typeof(FooImplementor)
.InheritsOrImplements(typeof(FooBase)), Is.True);
}
[Test]
public void Should_inherit_or_implement_any_base_type()
{
Assert.That(typeof(GenericFooImplementor<>)
.InheritsOrImplements(typeof(FooBase)), Is.True);
}

It seems to me that this implementation works in more cases (generic class and interface with or without initiated parameters, regardless of the number of child and parameters):
public static class ReflexionExtension
{
public static bool IsSubClassOfGeneric(this Type child, Type parent)
{
if (child == parent)
return false;
if (child.IsSubclassOf(parent))
return true;
var parameters = parent.GetGenericArguments();
var isParameterLessGeneric = !(parameters != null && parameters.Length > 0 &&
((parameters[0].Attributes & TypeAttributes.BeforeFieldInit) == TypeAttributes.BeforeFieldInit));
while (child != null && child != typeof(object))
{
var cur = GetFullTypeDefinition(child);
if (parent == cur || (isParameterLessGeneric && cur.GetInterfaces().Select(i => GetFullTypeDefinition(i)).Contains(GetFullTypeDefinition(parent))))
return true;
else if (!isParameterLessGeneric)
if (GetFullTypeDefinition(parent) == cur && !cur.IsInterface)
{
if (VerifyGenericArguments(GetFullTypeDefinition(parent), cur))
if (VerifyGenericArguments(parent, child))
return true;
}
else
foreach (var item in child.GetInterfaces().Where(i => GetFullTypeDefinition(parent) == GetFullTypeDefinition(i)))
if (VerifyGenericArguments(parent, item))
return true;
child = child.BaseType;
}
return false;
}
private static Type GetFullTypeDefinition(Type type)
{
return type.IsGenericType ? type.GetGenericTypeDefinition() : type;
}
private static bool VerifyGenericArguments(Type parent, Type child)
{
Type[] childArguments = child.GetGenericArguments();
Type[] parentArguments = parent.GetGenericArguments();
if (childArguments.Length == parentArguments.Length)
for (int i = 0; i < childArguments.Length; i++)
if (childArguments[i].Assembly != parentArguments[i].Assembly || childArguments[i].Name != parentArguments[i].Name || childArguments[i].Namespace != parentArguments[i].Namespace)
if (!childArguments[i].IsSubclassOf(parentArguments[i]))
return false;
return true;
}
}
Here are my 70 76 test cases:
[TestMethod]
public void IsSubClassOfGenericTest()
{
Assert.IsTrue(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(BaseGeneric<>)), " 1");
Assert.IsFalse(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(WrongBaseGeneric<>)), " 2");
Assert.IsTrue(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), " 3");
Assert.IsFalse(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(IWrongBaseGeneric<>)), " 4");
Assert.IsTrue(typeof(IChildGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), " 5");
Assert.IsFalse(typeof(IWrongBaseGeneric<>).IsSubClassOfGeneric(typeof(ChildGeneric2<>)), " 6");
Assert.IsTrue(typeof(ChildGeneric2<>).IsSubClassOfGeneric(typeof(BaseGeneric<>)), " 7");
Assert.IsTrue(typeof(ChildGeneric2<Class1>).IsSubClassOfGeneric(typeof(BaseGeneric<>)), " 8");
Assert.IsTrue(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(BaseGeneric<Class1>)), " 9");
Assert.IsFalse(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(WrongBaseGeneric<Class1>)), "10");
Assert.IsTrue(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric<Class1>)), "11");
Assert.IsFalse(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(IWrongBaseGeneric<Class1>)), "12");
Assert.IsTrue(typeof(IChildGeneric).IsSubClassOfGeneric(typeof(IBaseGeneric<Class1>)), "13");
Assert.IsFalse(typeof(BaseGeneric<Class1>).IsSubClassOfGeneric(typeof(ChildGeneric2<Class1>)), "14");
Assert.IsTrue(typeof(ChildGeneric2<Class1>).IsSubClassOfGeneric(typeof(BaseGeneric<Class1>)), "15");
Assert.IsFalse(typeof(ChildGeneric).IsSubClassOfGeneric(typeof(ChildGeneric)), "16");
Assert.IsFalse(typeof(IChildGeneric).IsSubClassOfGeneric(typeof(IChildGeneric)), "17");
Assert.IsFalse(typeof(IBaseGeneric<>).IsSubClassOfGeneric(typeof(IChildGeneric2<>)), "18");
Assert.IsTrue(typeof(IChildGeneric2<>).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "19");
Assert.IsTrue(typeof(IChildGeneric2<Class1>).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "20");
Assert.IsFalse(typeof(IBaseGeneric<Class1>).IsSubClassOfGeneric(typeof(IChildGeneric2<Class1>)), "21");
Assert.IsTrue(typeof(IChildGeneric2<Class1>).IsSubClassOfGeneric(typeof(IBaseGeneric<Class1>)), "22");
Assert.IsFalse(typeof(IBaseGeneric<Class1>).IsSubClassOfGeneric(typeof(BaseGeneric<Class1>)), "23");
Assert.IsTrue(typeof(BaseGeneric<Class1>).IsSubClassOfGeneric(typeof(IBaseGeneric<Class1>)), "24");
Assert.IsFalse(typeof(IBaseGeneric<>).IsSubClassOfGeneric(typeof(BaseGeneric<>)), "25");
Assert.IsTrue(typeof(BaseGeneric<>).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "26");
Assert.IsTrue(typeof(BaseGeneric<Class1>).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "27");
Assert.IsFalse(typeof(IBaseGeneric<Class1>).IsSubClassOfGeneric(typeof(IBaseGeneric<Class1>)), "28");
Assert.IsTrue(typeof(BaseGeneric2<Class1>).IsSubClassOfGeneric(typeof(IBaseGeneric<Class1>)), "29");
Assert.IsFalse(typeof(IBaseGeneric<>).IsSubClassOfGeneric(typeof(BaseGeneric2<>)), "30");
Assert.IsTrue(typeof(BaseGeneric2<>).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "31");
Assert.IsTrue(typeof(BaseGeneric2<Class1>).IsSubClassOfGeneric(typeof(IBaseGeneric<>)), "32");
Assert.IsTrue(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(BaseGenericA<,>)), "33");
Assert.IsFalse(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(WrongBaseGenericA<,>)), "34");
Assert.IsTrue(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "35");
Assert.IsFalse(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(IWrongBaseGenericA<,>)), "36");
Assert.IsTrue(typeof(IChildGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "37");
Assert.IsFalse(typeof(IWrongBaseGenericA<,>).IsSubClassOfGeneric(typeof(ChildGenericA2<,>)), "38");
Assert.IsTrue(typeof(ChildGenericA2<,>).IsSubClassOfGeneric(typeof(BaseGenericA<,>)), "39");
Assert.IsTrue(typeof(ChildGenericA2<ClassA, ClassB>).IsSubClassOfGeneric(typeof(BaseGenericA<,>)), "40");
Assert.IsTrue(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(BaseGenericA<ClassA, ClassB>)), "41");
Assert.IsFalse(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(WrongBaseGenericA<ClassA, ClassB>)), "42");
Assert.IsTrue(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA<ClassA, ClassB>)), "43");
Assert.IsFalse(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(IWrongBaseGenericA<ClassA, ClassB>)), "44");
Assert.IsTrue(typeof(IChildGenericA).IsSubClassOfGeneric(typeof(IBaseGenericA<ClassA, ClassB>)), "45");
Assert.IsFalse(typeof(BaseGenericA<ClassA, ClassB>).IsSubClassOfGeneric(typeof(ChildGenericA2<ClassA, ClassB>)), "46");
Assert.IsTrue(typeof(ChildGenericA2<ClassA, ClassB>).IsSubClassOfGeneric(typeof(BaseGenericA<ClassA, ClassB>)), "47");
Assert.IsFalse(typeof(ChildGenericA).IsSubClassOfGeneric(typeof(ChildGenericA)), "48");
Assert.IsFalse(typeof(IChildGenericA).IsSubClassOfGeneric(typeof(IChildGenericA)), "49");
Assert.IsFalse(typeof(IBaseGenericA<,>).IsSubClassOfGeneric(typeof(IChildGenericA2<,>)), "50");
Assert.IsTrue(typeof(IChildGenericA2<,>).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "51");
Assert.IsTrue(typeof(IChildGenericA2<ClassA, ClassB>).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "52");
Assert.IsFalse(typeof(IBaseGenericA<ClassA, ClassB>).IsSubClassOfGeneric(typeof(IChildGenericA2<ClassA, ClassB>)), "53");
Assert.IsTrue(typeof(IChildGenericA2<ClassA, ClassB>).IsSubClassOfGeneric(typeof(IBaseGenericA<ClassA, ClassB>)), "54");
Assert.IsFalse(typeof(IBaseGenericA<ClassA, ClassB>).IsSubClassOfGeneric(typeof(BaseGenericA<ClassA, ClassB>)), "55");
Assert.IsTrue(typeof(BaseGenericA<ClassA, ClassB>).IsSubClassOfGeneric(typeof(IBaseGenericA<ClassA, ClassB>)), "56");
Assert.IsFalse(typeof(IBaseGenericA<,>).IsSubClassOfGeneric(typeof(BaseGenericA<,>)), "57");
Assert.IsTrue(typeof(BaseGenericA<,>).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "58");
Assert.IsTrue(typeof(BaseGenericA<ClassA, ClassB>).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "59");
Assert.IsFalse(typeof(IBaseGenericA<ClassA, ClassB>).IsSubClassOfGeneric(typeof(IBaseGenericA<ClassA, ClassB>)), "60");
Assert.IsTrue(typeof(BaseGenericA2<ClassA, ClassB>).IsSubClassOfGeneric(typeof(IBaseGenericA<ClassA, ClassB>)), "61");
Assert.IsFalse(typeof(IBaseGenericA<,>).IsSubClassOfGeneric(typeof(BaseGenericA2<,>)), "62");
Assert.IsTrue(typeof(BaseGenericA2<,>).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "63");
Assert.IsTrue(typeof(BaseGenericA2<ClassA, ClassB>).IsSubClassOfGeneric(typeof(IBaseGenericA<,>)), "64");
Assert.IsFalse(typeof(BaseGenericA2<ClassB, ClassA>).IsSubClassOfGeneric(typeof(IBaseGenericA<ClassA, ClassB>)), "65");
Assert.IsFalse(typeof(BaseGenericA<ClassB, ClassA>).IsSubClassOfGeneric(typeof(ChildGenericA2<ClassA, ClassB>)), "66");
Assert.IsFalse(typeof(BaseGenericA2<ClassB, ClassA>).IsSubClassOfGeneric(typeof(BaseGenericA<ClassA, ClassB>)), "67");
Assert.IsTrue(typeof(ChildGenericA3<ClassA, ClassB>).IsSubClassOfGeneric(typeof(BaseGenericB<ClassA, ClassB, ClassC>)), "68");
Assert.IsTrue(typeof(ChildGenericA4<ClassA, ClassB>).IsSubClassOfGeneric(typeof(IBaseGenericB<ClassA, ClassB, ClassC>)), "69");
Assert.IsFalse(typeof(ChildGenericA3<ClassB, ClassA>).IsSubClassOfGeneric(typeof(BaseGenericB<ClassA, ClassB, ClassC>)), "68-2");
Assert.IsTrue(typeof(ChildGenericA3<ClassA, ClassB2>).IsSubClassOfGeneric(typeof(BaseGenericB<ClassA, ClassB, ClassC>)), "68-3");
Assert.IsFalse(typeof(ChildGenericA3<ClassB2, ClassA>).IsSubClassOfGeneric(typeof(BaseGenericB<ClassA, ClassB, ClassC>)), "68-4");
Assert.IsFalse(typeof(ChildGenericA4<ClassB, ClassA>).IsSubClassOfGeneric(typeof(IBaseGenericB<ClassA, ClassB, ClassC>)), "69-2");
Assert.IsTrue(typeof(ChildGenericA4<ClassA, ClassB2>).IsSubClassOfGeneric(typeof(IBaseGenericB<ClassA, ClassB, ClassC>)), "69-3");
Assert.IsFalse(typeof(ChildGenericA4<ClassB2, ClassA>).IsSubClassOfGeneric(typeof(IBaseGenericB<ClassA, ClassB, ClassC>)), "69-4");
Assert.IsFalse(typeof(bool).IsSubClassOfGeneric(typeof(IBaseGenericB<ClassA, ClassB, ClassC>)), "70");
}
Classes and interfaces for testing :
public class Class1 { }
public class BaseGeneric<T> : IBaseGeneric<T> { }
public class BaseGeneric2<T> : IBaseGeneric<T>, IInterfaceBidon { }
public interface IBaseGeneric<T> { }
public class ChildGeneric : BaseGeneric<Class1> { }
public interface IChildGeneric : IBaseGeneric<Class1> { }
public class ChildGeneric2<Class1> : BaseGeneric<Class1> { }
public interface IChildGeneric2<Class1> : IBaseGeneric<Class1> { }
public class WrongBaseGeneric<T> { }
public interface IWrongBaseGeneric<T> { }
public interface IInterfaceBidon { }
public class ClassA { }
public class ClassB { }
public class ClassC { }
public class ClassB2 : ClassB { }
public class BaseGenericA<T, U> : IBaseGenericA<T, U> { }
public class BaseGenericB<T, U, V> { }
public interface IBaseGenericB<ClassA, ClassB, ClassC> { }
public class BaseGenericA2<T, U> : IBaseGenericA<T, U>, IInterfaceBidonA { }
public interface IBaseGenericA<T, U> { }
public class ChildGenericA : BaseGenericA<ClassA, ClassB> { }
public interface IChildGenericA : IBaseGenericA<ClassA, ClassB> { }
public class ChildGenericA2<ClassA, ClassB> : BaseGenericA<ClassA, ClassB> { }
public class ChildGenericA3<ClassA, ClassB> : BaseGenericB<ClassA, ClassB, ClassC> { }
public class ChildGenericA4<ClassA, ClassB> : IBaseGenericB<ClassA, ClassB, ClassC> { }
public interface IChildGenericA2<ClassA, ClassB> : IBaseGenericA<ClassA, ClassB> { }
public class WrongBaseGenericA<T, U> { }
public interface IWrongBaseGenericA<T, U> { }
public interface IInterfaceBidonA { }

JaredPar's code works but only for one level of inheritance. For unlimited levels of inheritance, use the following code
public bool IsTypeDerivedFromGenericType(Type typeToCheck, Type genericType)
{
if (typeToCheck == typeof(object))
{
return false;
}
else if (typeToCheck == null)
{
return false;
}
else if (typeToCheck.IsGenericType && typeToCheck.GetGenericTypeDefinition() == genericType)
{
return true;
}
else
{
return IsTypeDerivedFromGenericType(typeToCheck.BaseType, genericType);
}
}

Here's a little method I created for checking that a object is derived from a specific type. Works great for me!
internal static bool IsDerivativeOf(this Type t, Type typeToCompare)
{
if (t == null) throw new NullReferenceException();
if (t.BaseType == null) return false;
if (t.BaseType == typeToCompare) return true;
else return t.BaseType.IsDerivativeOf(typeToCompare);
}

This can all be done easily with linq. This will find any types that are a subclass of generic base class GenericBaseType.
IEnumerable<Type> allTypes = Assembly.GetExecutingAssembly().GetTypes();
IEnumerable<Type> mySubclasses = allTypes.Where(t => t.BaseType != null
&& t.BaseType.IsGenericType
&& t.BaseType.GetGenericTypeDefinition() == typeof(GenericBaseType<,>));

Simple solution: just create and add a second, non-generic interface to the generic class:
public interface IGenericClass
{
}
public class GenericClass<T> : GenericInterface<T>, IGenericClass
{
}
Then just check for that in any way you like using is, as, IsAssignableFrom, etc.
if (thing is IGenericClass)
{
// Do work
{
Obviously only possible if you have the ability to edit the generic class (which the OP seems to have), but it's a bit more elegant and readable than using a cryptic extension method.

Added to #jaredpar's answer, here's what I use to check for interfaces:
public static bool IsImplementerOfRawGeneric(this Type type, Type toCheck)
{
if (toCheck.GetTypeInfo().IsClass)
{
return false;
}
return type.GetInterfaces().Any(interfaceType =>
{
var current = interfaceType.GetTypeInfo().IsGenericType ?
interfaceType.GetGenericTypeDefinition() : interfaceType;
return current == toCheck;
});
}
public static bool IsSubTypeOfRawGeneric(this Type type, Type toCheck)
{
return type.IsInterface ?
IsImplementerOfRawGeneric(type, toCheck)
: IsSubclassOfRawGeneric(type, toCheck);
}
Ex:
Console.WriteLine(typeof(IList<>).IsSubTypeOfRawGeneric(typeof(IList<int>))); // true

Updated Answer
This method checks if typeA equals, inherts (class : class), implements (class : interface) or extends (interface : interface) typeB. It accepts generic and non-generic interfaces and classes.
public static bool Satisfies(Type typeA, Type typeB)
{
var types = new List<Type>(typeA.GetInterfaces());
for (var t = typeA; t != null; t = t.BaseType)
{
types.Add(t);
}
return types.Any(t =>
t == typeB ||
t.IsGenericType && (t.GetGenericTypeDefinition() == typeB));
}
Used in the following it passes 74 of the 76 of the tests #Xav987's answer (It doesn't pass tests '68-3' and '69-3' but I think these tests imply List<Giraffe> is a subclass of List<Animal> and I don't think it is. E.g., List<Giraffe> cannot be cast to a List<Animal>, see https://stackoverflow.com/a/9891849/53252.)
public static bool IsSubClassOfGeneric(this Type typeA, Type typeB)
{
if (typeA == typeB)
{
return false;
}
return Satisfies(typeA, typeB);
}
Examples:
using System.Collections;
using System.Numerics;
void ShowSatisfaction(Type typeA, Type typeB)
{
var satisfied = Satisfies(typeA, typeB);
Console.WriteLine($"{satisfied}: [{typeA}] satisfies [{typeB}]");
}
ShowSatisfaction(typeof(object), typeof(string));
ShowSatisfaction(typeof(string), typeof(object));
ShowSatisfaction(typeof(string), typeof(IEnumerable));
ShowSatisfaction(typeof(string), typeof(IEnumerable<>));
ShowSatisfaction(typeof(string), typeof(IEnumerable<char>));
ShowSatisfaction(typeof(string), typeof(IEnumerable<int>));
ShowSatisfaction(typeof(int), typeof(object));
ShowSatisfaction(typeof(int), typeof(IComparable));
ShowSatisfaction(typeof(IReadOnlyDictionary<,>), typeof(IReadOnlyCollection<>));
ShowSatisfaction(typeof(bool), typeof(INumber<>));
ShowSatisfaction(typeof(int), typeof(INumber<>));
ShowSatisfaction(typeof(IBinaryInteger<>), typeof(IShiftOperators<,>));
ShowSatisfaction(typeof(IBinaryInteger<int>), typeof(IShiftOperators<,>));
ShowSatisfaction(typeof(IBinaryInteger<int>), typeof(IShiftOperators<int, int>));
Output:
False: [System.Object] satisfies [System.String]
True: [System.String] satisfies [System.Object]
True: [System.String] satisfies [System.Collections.IEnumerable]
True: [System.String] satisfies [System.Collections.Generic.IEnumerable`1[T]]
True: [System.String] satisfies [System.Collections.Generic.IEnumerable`1[System.Char]]
False: [System.String] satisfies [System.Collections.Generic.IEnumerable`1[System.Int32]]
True: [System.Int32] satisfies [System.Object]
True: [System.Int32] satisfies [System.IComparable]
True: [System.Collections.Generic.IReadOnlyDictionary`2[TKey,TValue]] satisfies [System.Collections.Generic.IReadOnlyCollection`1[T]]
False: [System.Boolean] satisfies [System.Numerics.INumber`1[TSelf]]
True: [System.Int32] satisfies [System.Numerics.INumber`1[TSelf]]
True: [System.Numerics.IBinaryInteger`1[TSelf]] satisfies [System.Numerics.IShiftOperators`2[TSelf,TResult]]
True: [System.Numerics.IBinaryInteger`1[System.Int32]] satisfies [System.Numerics.IShiftOperators`2[TSelf,TResult]]
True: [System.Numerics.IBinaryInteger`1[System.Int32]] satisfies [System.Numerics.IShiftOperators`2[System.Int32,System.Int32]]
INumber<> examples are from .NET 7 preview 5.
Previous Answer
It might be overkill but I use extension methods like the following. They check interfaces as well as subclasses. It can also return the type that has the specified generic definition.
E.g. for the example in the question it can test against generic interface as well as generic class. The returned type can be used with GetGenericArguments to determine that the generic argument type is "SomeType".
/// <summary>
/// Checks whether this type has the specified definition in its ancestry.
/// </summary>
public static bool HasGenericDefinition(this Type type, Type definition)
{
return GetTypeWithGenericDefinition(type, definition) != null;
}
/// <summary>
/// Returns the actual type implementing the specified definition from the
/// ancestry of the type, if available. Else, null.
/// </summary>
public static Type GetTypeWithGenericDefinition(this Type type, Type definition)
{
if (type == null)
throw new ArgumentNullException("type");
if (definition == null)
throw new ArgumentNullException("definition");
if (!definition.IsGenericTypeDefinition)
throw new ArgumentException(
"The definition needs to be a GenericTypeDefinition", "definition");
if (definition.IsInterface)
foreach (var interfaceType in type.GetInterfaces())
if (interfaceType.IsGenericType
&& interfaceType.GetGenericTypeDefinition() == definition)
return interfaceType;
for (Type t = type; t != null; t = t.BaseType)
if (t.IsGenericType && t.GetGenericTypeDefinition() == definition)
return t;
return null;
}

Building on the excellent answer above by fir3rpho3nixx and David Schmitt, I have modified their code and added the ShouldInheritOrImplementTypedGenericInterface test (last one).
/// <summary>
/// Find out if a child type implements or inherits from the parent type.
/// The parent type can be an interface or a concrete class, generic or non-generic.
/// </summary>
/// <param name="child"></param>
/// <param name="parent"></param>
/// <returns></returns>
public static bool InheritsOrImplements(this Type child, Type parent)
{
var currentChild = parent.IsGenericTypeDefinition && child.IsGenericType ? child.GetGenericTypeDefinition() : child;
while (currentChild != typeof(object))
{
if (parent == currentChild || HasAnyInterfaces(parent, currentChild))
return true;
currentChild = currentChild.BaseType != null && parent.IsGenericTypeDefinition && currentChild.BaseType.IsGenericType
? currentChild.BaseType.GetGenericTypeDefinition()
: currentChild.BaseType;
if (currentChild == null)
return false;
}
return false;
}
private static bool HasAnyInterfaces(Type parent, Type child)
{
return child.GetInterfaces().Any(childInterface =>
{
var currentInterface = parent.IsGenericTypeDefinition && childInterface.IsGenericType
? childInterface.GetGenericTypeDefinition()
: childInterface;
return currentInterface == parent;
});
}
[Test]
public void ShouldInheritOrImplementNonGenericInterface()
{
Assert.That(typeof(FooImplementor)
.InheritsOrImplements(typeof(IFooInterface)), Is.True);
}
[Test]
public void ShouldInheritOrImplementGenericInterface()
{
Assert.That(typeof(GenericFooBase)
.InheritsOrImplements(typeof(IGenericFooInterface<>)), Is.True);
}
[Test]
public void ShouldInheritOrImplementGenericInterfaceByGenericSubclass()
{
Assert.That(typeof(GenericFooImplementor<>)
.InheritsOrImplements(typeof(IGenericFooInterface<>)), Is.True);
}
[Test]
public void ShouldInheritOrImplementGenericInterfaceByGenericSubclassNotCaringAboutGenericTypeParameter()
{
Assert.That(new GenericFooImplementor<string>().GetType()
.InheritsOrImplements(typeof(IGenericFooInterface<>)), Is.True);
}
[Test]
public void ShouldNotInheritOrImplementGenericInterfaceByGenericSubclassNotCaringAboutGenericTypeParameter()
{
Assert.That(new GenericFooImplementor<string>().GetType()
.InheritsOrImplements(typeof(IGenericFooInterface<int>)), Is.False);
}
[Test]
public void ShouldInheritOrImplementNonGenericClass()
{
Assert.That(typeof(FooImplementor)
.InheritsOrImplements(typeof(FooBase)), Is.True);
}
[Test]
public void ShouldInheritOrImplementAnyBaseType()
{
Assert.That(typeof(GenericFooImplementor<>)
.InheritsOrImplements(typeof(FooBase)), Is.True);
}
[Test]
public void ShouldInheritOrImplementTypedGenericInterface()
{
GenericFooImplementor<int> obj = new GenericFooImplementor<int>();
Type t = obj.GetType();
Assert.IsTrue(t.InheritsOrImplements(typeof(IGenericFooInterface<int>)));
Assert.IsFalse(t.InheritsOrImplements(typeof(IGenericFooInterface<String>)));
}

JaredPar,
This did not work for me if I pass typeof(type<>) as toCheck. Here's what I changed.
static bool IsSubclassOfRawGeneric(Type generic, Type toCheck) {
while (toCheck != typeof(object)) {
var cur = toCheck.IsGenericType ? toCheck.GetGenericTypeDefinition() : toCheck;
if (cur.IsGenericType && generic.GetGenericTypeDefinition() == cur.GetGenericTypeDefinition()) {
return true;
}
toCheck = toCheck.BaseType;
}
return false;
}

#EnocNRoll - Ananda Gopal 's answer is interesting, but in case an instance is not instantiated beforehand or you want to check with a generic type definition, I'd suggest this method:
public static bool TypeIs(this Type x, Type d) {
if(null==d) {
return false;
}
for(var c = x; null!=c; c=c.BaseType) {
var a = c.GetInterfaces();
for(var i = a.Length; i-->=0;) {
var t = i<0 ? c : a[i];
if(t==d||t.IsGenericType&&t.GetGenericTypeDefinition()==d) {
return true;
}
}
}
return false;
}
and use it like:
var b = typeof(char[]).TypeIs(typeof(IList<>)); // true
There are four conditional cases when both t(to be tested) and d are generic types and two cases are covered by t==d which are (1)neither t nor d is a generic definition or (2) both of them are generic definitions. The rest cases are one of them is a generic definition, only when d is already a generic definition we have the chance to say a t is a d but not vice versa.
It should work with arbitrary classes or interfaces you want to test, and returns what as if you test an instance of that type with the is operator.

Type _type = myclass.GetType();
PropertyInfo[] _propertyInfos = _type.GetProperties();
Boolean _test = _propertyInfos[0].PropertyType.GetGenericTypeDefinition()
== typeof(List<>);

You can try this extension
public static bool IsSubClassOfGenericClass(this Type type, Type genericClass,Type t)
{
return type.IsSubclassOf(genericClass.MakeGenericType(new[] { t }));
}

late to the game on this... i too have yet another permutation of JarodPar's answer.
here's Type.IsSubClassOf(Type) courtesy of reflector:
public virtual bool IsSubclassOf(Type c)
{
Type baseType = this;
if (!(baseType == c))
{
while (baseType != null)
{
if (baseType == c)
{
return true;
}
baseType = baseType.BaseType;
}
return false;
}
return false;
}
from that, we see that it's not doing anything too cray cray and is similar to JaredPar's iterative approach. so far, so good. here's my version (disclaimer: not thoroughly tested, so lemme know if you find issues)
public static bool IsExtension(this Type thisType, Type potentialSuperType)
{
//
// protect ya neck
//
if (thisType == null || potentialSuperType == null || thisType == potentialSuperType) return false;
//
// don't need to traverse inheritance for interface extension, so check/do these first
//
if (potentialSuperType.IsInterface)
{
foreach (var interfaceType in thisType.GetInterfaces())
{
var tempType = interfaceType.IsGenericType ? interfaceType.GetGenericTypeDefinition() : interfaceType;
if (tempType == potentialSuperType)
{
return true;
}
}
}
//
// do the concrete type checks, iterating up the inheritance chain, as in orignal
//
while (thisType != null && thisType != typeof(object))
{
var cur = thisType.IsGenericType ? thisType.GetGenericTypeDefinition() : thisType;
if (potentialSuperType == cur)
{
return true;
}
thisType = thisType.BaseType;
}
return false;
}
basically this is just an extension method to System.Type - i did this to intentionally limit the "thisType" Type to concrete Types, as my immediate usage is to LINQ query "where" predicates against Type objects. i'm sure all you smart folks out there could bang it down to an efficient, all-purpose static method if you need to :) the code does a few things the answer's code doesn't
open's it up to to general "extension" - i'm considering inheritance (think classes)
as well as implementation (interfaces); method and parameter names
are changed to better reflect this
input null-validation (meah)
input of same type (a class cannot extend itself)
short-circuit execution if Type in question is an interface; because GetInterfaces() returns all implemented interfaces (even ones implemented in super-classes), you can simply loop through that collection not having to climb the inheritance tree
the rest is basically the same as JaredPar's code

Determine which genric type object is derived from

I have the following classes:
public abstract class CommandBase
{
... Stuff
}
public abstract class Command<TArgumentType>
: CommandBase where TArgumentType : class
{
protected TArgumentType Argument { get; private set; }
protected Command(TArgumentType argument)
{
Argument = argument;
}
}
public abstract class Command<TArgumentType, TReturnType>
: Command<TArgumentType> where TArgumentType : class
{
public TReturnType ReturnValue{ get; protected set; }
protected Command(TArgumentType argument) : base(argument)
{
}
}
How do I determine if an object is of type Command<TArgumentType> or Command<TArgumentType, TReturnType>? I don't know what specific types TArgumentType or TReturnType are. Or should I just do a simple try/catch around:
var returnValue = object.ReturnValue;

If you don't know the type at compile-time, then foo.ReturnValue won't even compile, unless it's of type dynamic.
You can use something like this:
static bool ContainsGenericClassInHierarchy(object value,
Type genericTypeDefinition)
{
Type t = value.GetType();
while (t != null)
{
if (t.IsGenericType
&& t.GetGenericTypeDefinition() == genericTypeDefinition)
{
return true;
}
t = t.BaseType;
}
return false;
}
Call it like this:
// Single type parameter
bool x = ContainsGenericClassInHierarchy(foo, typeof(Command<>));
// Two type parameters
bool y = ContainsGenericClassInHierarchy(foo, typeof(Command<,>));
Note that this won't work for finding implemented interfaces, which is somewhat trickier.

How to test whether two generics have a base-subclass relationship without instantiating them?

I have the following generic classes:
class Base<T> where T : ... { ... }
class Derived<T> : Base<T> where T : ... { ... }
class Another<T> where T : ... { ... }
class DerivedFromDerived<T> : Derived<T> where T : ... { ... }
Somewhere in my code, I would like to test whether a given generic inherits from Base<T>, without creating a particular instance of the generic. How do I do that?
static bool DerivedFromBase(Type type) { /* ??? */ }
static void Main(string[] args)
{
Console.WriteLine(DerivedFromBase(typeof(Derived<>))); // true
Console.WriteLine(DerivedFromBase(typeof(Another<>))); // false
Console.WriteLine(DerivedFromBase(typeof(DerivedFromDerived<>))); // true
Console.ReadKey(true);
}
EDIT: Thank you Mark. Now I see the light. I originally tried the following:
typeof(Derived<>).BaseType == typeof(Base<>)
Apparently, this is correct. But it is not. The problem is that Base's T is not the same thing as Derived's T. So, in
typeof(Base<>)
Base's T is a free type. But, in
typeof(Derived<>).BaseType
Base's T is bound to Derived's T, which is in turn a free type. (This is so awesome I would LOVE to see the System.Reflection's source code!) Now,
typeof(Derived<>).BaseType.GetGenericTypeDefinition()
unbounds Base's T. Conclusion:
typeof(Derived<>).BaseType.GetGenericTypeDefinition() == typeof(Base<>)
And now, if you all excuse me, my head is burning.

Not sure if this is what you are looking for but I think "IsAssignableFrom" will do the trick.
class Program
{
class Base<T> { }
class Derived<T> : Base<T> { }
class Another<T> { }
class DerivedFromDerived<T> : Derived<T> { }
static bool DerivedFromBase<T>(Type type)
{
return typeof(Base<T>).IsAssignableFrom(type);
}
static void Main(string[] args)
{
Console.WriteLine(DerivedFromBase<int>(typeof(Derived<int>))); // true
Console.WriteLine(DerivedFromBase<int>(typeof(Another<int>))); // false
Console.WriteLine(DerivedFromBase<int>(typeof(DerivedFromDerived<int>))); // true
Console.ReadKey(true);
}
}
To handle the open base type:
static bool DerivedFromBase(Type type)
{
Type openBase = typeof(Base<>);
var baseType = type;
while (baseType != typeof(Object) && baseType != null)
{
if (baseType.GetGenericTypeDefinition() == openBase) return true;
baseType = baseType.BaseType;
}
return false;
}

I've come up with this version, although it seems a little hacky.
private static bool IsDerivedFrom(Type derivedType, Type baseType)
{
if (derivedType.BaseType == null)
return false;
if (derivedType.BaseType.GUID == baseType.GUID)
return true;
return IsDerivedFrom(derivedType.BaseType, baseType);
}
It relies on all types having different GUIDs, which should be true, but obviously a collision will happen next Thursday.