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C# How to create a collection of generic class which derives from a specific implementation of another generic class which is a derived class

Struggling with wording that title to make any sense so I will just show my code and try and explain it
So I have this base class
public abstract class SpacecraftProperty
{
}
public abstract class SpacecraftProperty<T> : SpacecraftProperty
where T : SpacecraftProperty<T>
{
public abstract void Add(T property);
}
With this I can create a collection of SpacecraftProperty just fine thanks to the base SpacecraftProperty class that is not generic.
Then I have this class that derives from SpacecraftProperty that is also generic
public class ResourceStorage<ResourceType> : SpacecraftProperty<ResourceStorage<ResourceType>>
where ResourceType : ResourceInfo, new()
{
public ResourceType resource { get; private set; } = new ResourceType();
public float capacity { get; private set; }
public override void Add(ResourceStorage<ResourceType> property)
{
this.capacity += property.capacity;
}
}
Now the issus is that I need to create a collection of this ResourceStorage class, where each object in the collection can be of any type for ResourceType. But I can't use the same trick as above where I create a non-generic base class as then when I try and derive from SpacecraftProperty<>, it won't know what type of the generic SpacecraftProperty to derive from.
For completeness, here is the code for ResourceInfo, which is an abstract class which will be derived from
public abstract class ResourceInfo
{
public abstract string GetName();
public abstract string GetDescription();
}
So in summary I would for example want a collection that contains say a ResourceStorage<SomeTypeA>, ResourceStorage<SomeTypeB> etc. where SomeTypeA and SomeTypeB derive from ResourceInfo. And ResourceStorage derives from SpacecraftProperty, which has the generic method Add.
Any ideas?

But I can't use the same trick as above where I create a non-generic base class as then when I try and derive from SpacecraftProperty<>, it won't know what type of the generic SpacecraftProperty to derive from.
You can use the same trick. The type to derive from is SpacecraftProperty<ResourceStorage>, where ResourceStorage is the non-generic type you have created. This is because the implementation of Add in the generic ResourceStorage<T> doesn't actually use T.
// note that I've changed the naming conventions to match that of C#'s
public abstract class ResourceStorage: SpacecraftProperty<ResourceStorage> {
public abstract float Capacity { get; protected set; }
}
public class ResourceStorage<TResource> : ResourceStorage
where TResource: ResourceInfo, new()
{
public TResource Resource { get; private set; } = new TResource();
public override float Capacity { get; protected set; }
public override void Add(ResourceStorage property)
{
Capacity += property.Capacity;
}
}
ResourceStorage<TResource> is now a SpacecraftProperty<ResourceStorage>, however, and not a SpacecraftProperty<ResourceStorage<TResource>>.
To fix that, you can make the abstract classes contravariant interfaces instead. Since there is only one Add method:
public interface ISpacecraftProperty {}
public interface ISpacecraftProperty<in T> : ISpacecraftProperty
where T : ISpacecraftProperty<T>
{
void Add(T property);
}
public interface IResourceStorage: ISpacecraftProperty<IResourceStorage> {
public float Capacity { get; }
}
public class ResourceStorage<TResource> : IResourceStorage
where TResource: ResourceInfo, new()
{
public TResource Resource { get; private set; } = new TResource();
public float Capacity { get; private set; }
public void Add(IResourceStorage property)
{
Capacity += property.Capacity;
}
}
Now this compiles:
var list = new List<IResourceStorage>() {
new ResourceStorage<Foo>(),
new ResourceStorage<Bar>()
};
// This'd work too, but I'm sure you are aware already, since it is the nature of what you are trying to do
list[0].Add(list[1]);
ISpacecraftProperty<ResourceStorage<Foo>> x = new ResourceStorage<Foo>();
If ISpacecraftProperty has other methods that return a T, and so can't be contravariant, you can always just add ISpacecraftProperty<ResourceStorage<TResource>> as yet another interface of ResourceStorage<TResource>.
public class ResourceStorage<TResource> : IResourceStorage, ISpacecraftProperty<ResourceStorage<TResource>>
where TResource: ResourceInfo, new()
{
public TResource Resource { get; private set; } = new TResource();
public float Capacity { get; private set; }
public void Add(IResourceStorage property)
{
Capacity += property.Capacity;
}
// implement explicitly by delegation
void ISpacecraftProperty<ResourceStorage<TResource>>.Add(ResourceStorage<TResource> property) {
Add(property);
}
}

Cannot add a derived class object to a list of it's base class type

I have the following class structure:
//BaseClass
public abstract class BaseClass<T> where T : Model
{
public abstract T Data { get; set; }
public BaseClass(T data) { Data = data; }
}
public abstract class Model
{
public int Id { get; set; }
}
//ClassA
public class BaseClassA : BaseClass<ModelA>
{
public override ModelA Data { get; set; }
public BaseClassA(ModelA data) : base(data) { }
}
public class ModelA : Model { }
//ClassB
public class BaseClassB : BaseClass<ModelB>
{
public override ModelB Data { get; set; }
public BaseClassB(ModelB data) : base(data) { }
}
public class ModelB : Model { }
I would like to use them as follows:
List<BaseClass<Model>> myBaseList = new List<BaseClass<Model>>();
myBaseList.Add(new BaseClassA(new ModelA()));
myBaseList.Add(new BaseClassB(new ModelB()));
foreach (var item in myBaseList)
{
if (item.Data.Id > 0)
{
//do stuff
}
}
But I get the compiler exception:
cannot convert from BaseClassA to BaseClass<Model>
However, I was under the impresion that BaseClassA being of type BaseClass<ModelA> would be meet the requirement of being of type BaseClass<Model>.
For instance, this doesn't generate any errors:
List<Model> myModelList = new List<Model>();
myModelList.Add(new ModelA());
myModelList.Add(new ModelB());
I can't seem to wrap my head around where I went wrong with this.

One possible solution would be to introduce a covariant interface:
public interface IBase<out T> where T : Model
{
T Data { get; }
}
public abstract class BaseClass<T> : IBase<T> where T : Model
Then use the interface for your list:
var myBaseList = new List<IBase<Model>>();
myBaseList.Add(new BaseClassA(new ModelA()));
myBaseList.Add(new BaseClassB(new ModelB()));
Because IBase declares Data as get-only, this ensures type-safety.
And here you still have access to Data:
foreach (var item in myBaseList)
{
if (item.Data.Id > 0)
{
//do stuff
}
}

Specify Generic type and interface

I need to have a list where all items extend class A and implement interface I. Additionally class A might be multiple parents up in the hierarchy.
If all the classes were direct descendants of class A I could just use an Abstract class that implements I as the generic and use that, but my use case doesn't allow for this.
is there a way to tell a List that its elements must both extend class A and implement interface I ? List<A,I> ? If not is there another way around this?
Example Code:
public class A
{
// Class belongs to a third party library
}
public class B : A
{
// Class belongs to a third party library
public string Text{ get; set; }
}
public class C : A
{
// Class belongs to a third party library
public string Other{ get; set; }
}
interface I
{
// Belongs to me
bool shouldSend();
string getName();
string getValue();
}
public class MyClass : B, I
{
public string Name{ get; set; }
public function myClass(ObjectWithName obj)
{
Name = obj.Name;
}
public string getValue()
{
return Text;
}
public bool shouldSend()
{
return true;
}
}
public class MyClass2 : C, I
{
public string Name{ get; set; }
public function myClass(ObjectWithName obj)
{
Name = obj.Name;
}
public string getValue()
{
return Other;
}
public bool shouldSend()
{
return true;
}
}
public class mainActions
{
// Here is where I need the list to use both restrictions
public List<A,I> myList;
// The class I need to use these things in
public function mainActions(List<ObjectWithName> elements)
{
ThirdPartyCollection TPC = new ThirdPartyCollection();
foreach(var el in elements)
{
MyList.Add(new MyClass(el));
MyList.Add(new MyClass2(el));
// TPC.Add accepts implementations of A here
TPC.Add(MyList.ElementAt(MyList.Count - 1));
TPC.Add(MyList.ElementAt(MyList.Count - 2));
}
}
public function doThisLater()
{
foreach(var el in myList)
{
if(el.shouldSend())
{
// I need an implementation of I here
doSomethingElse(el.getName(), el.getValue());
}
}
}
}
EDIT: For anyone coming in search of an answer here in the future, it doesn't seem to be possible. Instead I used #servys answer and made a new list to hold my sub class objects:
public class MyList<T> : List<T> where T : A, I
{
}
Then I kept different lists for each subclass:
protected MyList<MyClass> MCList = new MyList<MyClass>();
protected MyList<MyClass2> MCList2 = new MyList<MyClass2>();

When you specify generic constraints you can specify as many as you want, and all of them must be met, so you can simply add a generic constraint of A and I to your type, and a type has to meet both of those constraints to be a valid generic argument.
public class ClassThatNeedsABetterName<T> : List<T>
where T : A, I
{ }

Getting properties from generic type used in abstract superclass without using interfaces?

Is there any nice, elegant way to get properties from generic type used in abstract superclass without using interfaces?
Here's an example:
public abstract class CoolBase<T>
where T : class
{
private IEnumerable<T> somEnumerable;
public void GetPersonProperties()
{
var name = somEnumerable.First().Name; //this doesn't work
}
}
public class CoolA : CoolBase<Person>
{
}
public class Person
{
public string Name { get; set; }
public string Region { get; set; }
}
}

The goal of using generic classes is type-flexibility -
therefore it makes no sence to declare a method in a generic class which
uses Person-specific methods.
You should implement such detailed methods in the concrete implementations of
your abstract, generic class (here CoolA).
Maybe it is helpful for you to declare an abstract method getProperties()
int the generic, abstract class, wich can be implemented in CoolA via using
Person-specific code.
public abstract class CoolBase<T>
where T : class
{
private IEnumerable<T> somEnumerable;
public abstract void getProperties();
}
public class CoolA : CoolBase<Person>
{
public override void getProperties()
{
//should work, somEnumberable is made of Persons here
var name = somEnumerable.First().Name;
}
}

It makes no sense to put GetPersonProperties in CoolBase. CoolBase is generic, so should not have a class-specific functionality within it.
You could create a abstract method in CoolBase and implement it in your derived type:
public abstract class CoolBase<T> where T : class
{
protected IEnumerable<T> somEnumerable;
public abstract void GetProperties();
}
public class CoolA : CoolBase<Person>
{
public override void GetProperties()
{
var name = somEnumerable.First().Name;
}
}
public class Person
{
public string Name { get; set; }
public string Region { get; set; }
}
Alternatively, you could you reflection to get at the properties of T at runtime:
public abstract class CoolBase<T> where T : class
{
private IEnumerable<T> somEnumerable;
public void GetProperties()
{
foreach (var prop in typeof (T).GetProperties())
{
// do something with each property
}
}
}

How Can I Accept a Generic Class and Use Its Properties / Methods

I want to create a class that could hold any of a number of same type of classes. For example lets says I have a base class like follows:
public class BaseClass
{
public string MyBaseString
{
get;
set;
}
}
And then I have a few derived classes like this:
public class DerivedClass : BaseClass
{
public MyDerivedClassString
{
get;
set;
}
}
public class DerivedClass2 : BaseClass
{
public MyDerivedClass2String
{
get;
set;
}
}
Now I would like a class that accepts one of these implementations and does stuff with it. Here is the only thing I can think of, but there must be a better way:
public class ClassA
{
public object MyClass
{
get;
set;
}
public ClassA (object myClass)
{
MyClass = myClass;
if (object is BaseClass)
{
//do something
}
else if (object is DerivedClass)
{
//do something specific to derived class
}
else if (object is DerivedClass2)
{
//do something specific to derived class 2
}
}
}
CLARIFICATION: The specific goal I am trying to accomplish is to use ClassA as a container class for various implementations of the BaseClass. The business goal I am trying to accomplish is to create a Legend object which might use multiple color schemes (i.e. a Mono Color Ramp, Multi Color Ramp, etc). So I would like the Legend class to contain the ColorScheme that is being used, but still have access to that color scheme's unique properties for modification later on.
CLARIFICATION 2 Based on the wide array of responses I got, I thought I'd provide an exact replication of what I'm trying to do:
public class BaseColorScheme
{
List<Color> _colors = new List<Color>();
public List<Color> Colors
{
get
{
return _colors;
}
set
{
_colors = value;
}
}
}
public class SingleColorScheme : BaseColorScheme
{
public Color MidColor
{
get;
set;
}
public SingleColorScheme( Color midColor, int numberOfClassifications )
{
Colors = CreateMonoColorRamp( midColor, numberOfClassifications );
}
}
public class MultiColorScheme : BaseColorScheme
{
public Color StartColor
{
get;
set;
}
public Color EndColor
{
get;
set;
}
public Color MidColor
{
get;
set;
}
public MultiColorScheme( Color startColor, Color endColor, Color midColor )
{
StartColor = startColor;
EndColor = endColor;
MidColor = midColor;
Colors = //do something to define multi color scheme
}
}
Then I would have a Legend Class that would be something like
public class Legend
{
public object ColorScheme
{ get; set; }
public Guid LegendId
{ get; set; }
public Legend(object colorScheme)
{
ColorScheme = colorScheme;
}
}
Finally I might have a form that sits on top of the legend that displays the properties of the various color schemes based on which type of color scheme it is. Hopefully that helps clarify a bit.

public class ClassA<T> where T : BaseClass
{
public T MyClass { get; set; }
public ClassA(T myClass) { MyClass = myClass; }
}
Beyond that, define the common interface of the class hierarchy either as an interface or as methods (concrete, abstract, or virtual) within the base class. Then you can be assured all derived classes have such method / properties and can use them within your generic wrapper.

Instead of letting ClassA perform whatever needs to be done, you can use polymorphism and let the classes do it to themselves.
Simply declare a virtual method in the base class, have it do whatever you need it do so, and then override this method in the subclasses. In the method in ClassA, you just need to call that method on the object you receive as a parameter - without having to care about the specific type.

If you need to access different properties based on which derived class is passed something like this should help:
public class ClassA<T> where T : BaseClass
{
public T MyClass { get; set; }
public ClassA(T myClass) { MyClass = myClass; }
public void DoStuffToMyClass()
{
if(MyClass is BaseClass)
{ // do base class stuff }
else if(Myclass is DerivedClass)
{ // do DerivedClass stuff }
else if(MyClass is DerivedClass2)
{ // do DerivedClass2 stuff }
}
}
This gives you the type saftey to ensure you at least have the BaseClass object, and possibly a derived class.

The answer is polymorphism, let the object do it themselves.
public class BaseClass
{
public string MyString { get; set; }
public virtual string DoIt()
{
return "I'm Base Class";
}
}
public class DerivedClassA
{
public override string DoIt()
{
return "I'm Derived Class A";
}
}
public class DerivedClassB
{
public override string DoIt()
{
return "I'm Derived Class B";
}
}
....
public ClassA (BaseClass myClass)
{
MyClass = myClass;
MyClass.DoIt();
}
.....
ClassA x1 = ClassA(new BaseClass()) // calls BaseClass.DoIt()
ClassA x2 = ClassA(new DerivedClassA()) // calls DerivedClassA.DoIt()
ClassA x3 = ClassA(new DerivedClassB()) // calls DerivedClassB.DoIt()
whenever you catch yourself acting differently based on the run-time type of the object, you are dealing with code that breaks OO principles, i.e. a class that does not respect the base class contract.

Can you use virtual methods?
public abstract class BaseClass
{
public abstract void DoStuff();
}
public class DerivedClass1 : BaseClass
{
public override void DoStuff()
{
...
}
}
public class DerivedClass2 : BaseClass
{
public override void DoStuff()
{
...
}
}
Without generics:
public class ClassA
{
public BaseClass MyClass
{
get;
set;
}
public ClassA (BaseClass myClass)
{
MyClass = myClass;
myClass.DoStuff();
}
}
or with generics:
public class ClassA<T> where T : BaseClass
{
public T MyClass { get; set; }
public ClassA (T myClass)
{
MyClass = myClass;
myClass.DoStuff();
}
}

Keep it simple: polymorphism
Hopefully your objects have a common interface, something like:
class Base {
public virtual void DoSomething() { /* Default implementation */ }
}
class Derived1 : Base {
public override void DoSomething() { /* Implementation specific to this type */ }
}
class Derived2 : Base {
public override void DoSomething() { /* Another implementation specific to this type */ }
}
Or maybe they implement a common interface. So hopefully your consuming class can hold the most general representation of your inputs as possible and invoke code as such:
class Dependent {
public Dependent(Base instance) {
instance.DoSomething();
}
}
So your Dependent class doesn't really are whether it has a derived type or a base type.
Not quite as simple: visitor pattern
Sometimes polymorphism doesn't really work, which is particularly the case if you need to access the specific members of your derived classes, and those members aren't in the base class. Visitor pattern works well in this case, especially if you have a fixed, well-defined graph of objects.
public interface IVisitor<T> {
T Visit(Base x);
T Visit(Derived1 x);
T Visit(Derived2 x);
}
class Base {
public virtual T Accept<T>(IVisitor<T> visitor) { visitor.Visit(this); }
public string BaseString { get; set; }
}
class Derived1 : Base {
public override T Accept<T>(IVisitor<T> visitor) { visitor.Visit(this); }
public string Derived1String { get; set; }
}
class Derived2 : Base {
public override T Accept<T>(IVisitor<T> visitor) { visitor.Visit(this); }
public string Derived2String { get; set; }
}
So Derived1 and Derived2 have a different set of properties, and if you need to get to those properties without a runtime type-checking, implement a visitor:
class DefaultStringVisitor : IBaseVisitor<string> {
public string Visit(Base x) { return x.BaseString; }
public string Visit(Derived1 x) { return x.Derived1String; }
public string Visit(Derived2 x) { return x.Derived2String; }
}
class Dependent {
public Dependent(Base x) {
string whatever = x.Accept<string>(new DefaultStringVisitor());
}
}
So the visitor pattern gives you access to your derived object's members without a type-check. Its a somewhat inflexible pattern (i.e. need to know which objects to visit up front), but it might work for your needs.