This question already has answers here:
Can I use reflection to inspect the code in a method?
(7 answers)
Closed 16 days ago.
I want to compare if two methods have the same body and the same method signature. I want to also make sure they have the same attributes above the method.
Is there a way to get the method body info? I am aware I can get the attributes easily but I tried using reflection and did not see a way. Below are two examples.
This should return that they are the same
[TestCase("a")]
public void Foo1(string a)
{
Assert.True(true);
}
[TestCase("a")]
public void Foo1(string a)
{
Assert.True(true);
}
This should return that they are not the same since an extra attribute
[TestCase("a")]
public void Foo1(string a)
{
Assert.True(true);
}
[TestCase("a")]
[TestCase("aa")]
public void Foo1(string a)
{
Assert.True(true);
}
This should return that they are not the same since the method body is different
[TestCase("a")]
public void Foo1(string a)
{
Assert.True(true);
}
[TestCase("a")]
public void Foo1(string a)
{
Assert.That(a, Is.EqualTo("a"));
}
By parsing source code only. Even reflection does not meet your requirements
Related
This question already has answers here:
Pass Method as Parameter using C#
(13 answers)
Closed 3 years ago.
(I'm a bit new to programming so if this doesn't make sense just say so)
Let's say that a method takes in a void as parameter. Ex:
method(anotherMethod);
and I want to write the void inside of the brackets rather than writing the void and putting the name inside so rather than
void theVoid() {
doSomethingHere;
}
and then calling it like
method(theVoid());
I wanted to do
method({ doSomethingHere; })
directly, is it possible to do so?
The thing you are trying to do is called "lambda" it's anonymous functions
Here is the documentation for that.
https://learn.microsoft.com/en-us/dotnet/csharp/programming-guide/statements-expressions-operators/lambda-expressions
Your method will need to be passed a Delegate (if you do not return anything, an Action should be fine)
https://learn.microsoft.com/en-us/dotnet/api/system.action-1?view=netcore-2.2
Method(TheVoid()); // does not compile
Method(TheVoid); // compiles
using System;
public class Example
{
public void Method(Action func)
{
func();
}
public void TheVoid()
{
Console.WriteLine("In example.TheVoid");
}
}
public class Program
{
public static void TheVoid()
{
Console.WriteLine("In TheVoid");
}
public static void Main()
{
var example = new Example();
example.Method(example.TheVoid);
example.Method(() => {
Console.WriteLine("In lambda");
});
example.Method(TheVoid);
}
}
Example of what you are trying to do
I have an object that can be of type AudioRequest or VideoRequest. Both classes inherit from Request. I have this class:
public static DoThings
{
public static void HandleRequest(AudioRequest r)
{
// Do things.
}
public static void HandleRequest(VideoRequest r)
{
// Do things.
}
}
I want to be able to call DoThings.HandleRequest(r) where r can be either a VideoRequest or AudioRequest and have it call the correct one. Is that possible? I have no control over the *Request classes, so I can't do anything to them. I do have control of the DoThings class and the code that calls HandleRequest. This is the code that calls it, it is WebAPI:
public Response Post(Request input)
{
return DoThings.HandleRequest(input);
}
The code above gives the error Argument 1: cannot convert from 'Request' to 'AudioRequest'.
The original code that I was cleaning up had this:
if (input.GetType() == typeof(AudioRequest))
{
var audioRequest = (AudioRequest)input;
DoThings.HandleRequest(audioRequest);
}
else if (input.GetType() == typeof(VideoRequest))
{
var videoRequest = (VideoRequest)input;
DoThings.HandleRequest(videoRequest);
}
But I figured there was a cleaner way to do this.
Based on the information you've provided so far, your question appears to be a duplicate of How to call a function dynamically based on an object type. I agree with the answer, that the fact that you want to do this suggests you should rethink the design. But, you can use dynamic to accomplish what you want.
Here's a simple console program that demonstrates the basic idea:
class Program
{
static void Main(string[] args)
{
A b = new B(), c = new C();
M(b);
M(c);
}
static void M(A a)
{
WriteLine("M(A)");
M((dynamic)a);
}
static void M(B b)
{
WriteLine("M(B)");
}
static void M(C c)
{
WriteLine("M(C)");
}
}
class A { }
class B : A { }
class C : A { }
The output is:
M(A)
M(B)
M(A)
M(C)
As you can see, in each case the M(A) method is called first, and then the appropriate M(B) or M(C) overload is called from M(A).
In your own example, this could look something like this:
public static DoThings
{
public static void HandleRequest(Request r)
{
// Dynamic dispatch to actual method:
HandleRequest((dynamic)r);
}
public static void HandleRequest(AudioRequest r)
{
// Do things.
}
public static void HandleRequest(VideoRequest r)
{
// Do things.
}
}
Note that dynamic does incur a run-time cost, particularly the first time a method is called with a given run-time type. But depending on the frequency and complexity of these "requests", using dynamic could be the cleanest way out of the current situation.
C# will call the appropriate function that matches the arguments and their types.
That being said, both of your functions accept AudioRequest, I believe one of those should accept a VideoRequest.
public static DoThings
{
public static void HandleRequest(AudioRequest r)
{
// Do things.
}
public static void HandleRequest(VideoRequest r)
{
// Do things.
}
}
If for some reason you must have two different functions that take only AudioRequest you can differentiate between two function with an extra parameter
public static class DoThings
{
public static void HandleRequest(AudioRequest r)
{
// Do things.
}
public static void HandleRequest(AudioRequest r, bool UseAlternativeMethod)
{
// Do other things.
}
}
Simply having a second parameter will call the second method regardless of it's value.
This isn't a best practices solution as you'd rather discriminate between them by accurately renaming the method name to be accurate but in practice you don't always have a choice.
This question already has answers here:
C# params keyword with two parameters of the same type
(5 answers)
Closed 6 years ago.
I'm trying to make a log plugin for myself and I want to have a method where I overload it with different parameters.
The key is, it needs to be possible to add multiple strings, which I will print on different lines. I like the idea of using params, that way I don't need to add string[] { strings here } everytime.
The issue I currently have is that the Log.L() method will not trigger the first, but the second method, which kinda makes sense.
How can I solve this issue, while keeping the params?
Log.L("line1", "line2", "line3");
public static class Log
{
public static void L(params string[] message)
{
Write(LogType.Log, message);
}
public static void L(string location, params string[] message)
{
Write(LogType.Log, message, false, location);
}
}
It will always assume that the first string is location so, just use the second overload:
public static void L(string location, params string[] message)
{
Write(LogType.Log, message, false, location);
}
you can simply pass null or empty string when location is not available and deal with it in the method.
You can create two classes and use them to differentiate between the two overloads. You can even go so far as having one class inherit from the other if you want.
public class LoginWithMessages {
public string[] Messages {get; set;}
}
public class LoginWithLocation : LoginWithMessages {
public string Location {get; set;}
}
Then your method signatures will be:
public static void L(LoginWithMessages loginMessage)
public static void L(LoginWithLocation loginLocation)
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Closed 7 years ago.
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It makes no sense to me why C# doesn't support static methods & static properties in interfaces. In a brief survey of other SO questions on the issue, I come across a variety of answers ranging from "it's apparently an oversight in the design of C# and/or the CLR, and fixing it would break existing code" all the way to "interfaces are meant to interact with objects, and if you find yourself wanting to use interfaces otherwise, you're obviously lacking grey matter and should probably go back to sweeping floors". This question exhibits the full range of such answers.
I need a family of parsers, each with a method that determines if the assembly file contents passed to it matches its platform type. These are stateless entities; there's no reason to have "objects" of these parsers other than that C# interfaces require class instances. If I rip out all the "static" keywords below, this code compiles without error.
public interface IParser
{
static string platformName { get; }
static bool isThisPlatform(string asmFileContents);
static bool parseAsm(string asmFileContents);
}
class PIC32MX_GCC_Parser : IParser
{
public static string platformName { get { return "PIC32MX_GCC"; } }
public static bool isThisPlatform(string asmFileContents)
{
return false; // stub
}
public static bool parseAsm(string asmFileContents)
{
return false; // stub
}
}
class M16C_IAR_Parser : IParser
{
public static string platformName { get { return "M16C_IAR"; } }
public static bool isThisPlatform(string asmFileContents)
{
return false; // stub
}
public static bool parseAsm(string asmFileContents)
{
return false; // stub
}
}
IParser[] parsers =
{
new PIC32MX_GCC_Parser(),
new M16C_IAR_Parser()
};
public IParser findTheRightParser(string asmFileContents)
{
foreach(IParser parser in parsers)
{
if (parser.isThisPlatform(asmFileContents))
{
Console.WriteLine("Using parser: ", parser.platformName);
return parser;
}
}
return null;
}
I'd like to ask why C# won't let me do this, but I know the answer is just "because it doesn't." I know the "workaround" is to just implement them as instance methods which, if necessary, call a static method (which isn't actually necessary in this case).
Since there are a number of people out there (many with high SO rep) who think that putting static methods in interfaces makes no logical sense and if you want to do so there's something wrong with your design, or your head (or both), I'd like some of those people to help me out & give me a good, simple alternative to my code above which uses static methods and doesn't simply "work around" the issue by having instance methods wrap static methods.
There is a need for objects because what you appear to be looking for is dynamic dispatch- you want to be able to call a method on an interface (IParser.Parse), but have the implementation of the method defined by the concrete implementation of the interface. This is classic OOP, and C# (as well as Java) only supports it via instance methods. Singletons eliminate the need for an allocation per call, so that's a good approach. Alternatively you cal use static classes and static methods- but then you are limited to static dispatch, because the caller must know which implementation to call.
In short- it isn't a C# limitation. It's a limitation of most if not all object oriented programming languages.
There are many examples of singleton implementations in the C# literature (for example: http://www.dotnetperls.com/singleton).
To come up with other alternatives requires changing the way that you select your parser. For example, if you wanted to select it via an enum:
enum ParserType {
PIC32MX_GCC,
M16C_IAR,
Other_Parser,
}
Then something like this will work:
public static bool parseAsm(ParserType type, string asmFileContents) {
switch type {
case PIC32MX_GCC:
return PIC32MX_GCC_Parser.ParseAsm(asmFileContents);
case M16C_IAR:
return M16C_IAR_Parser.ParseAsm(asmFileContents);
default:
throw new NotImplementedException("I dont know this parser type");
}
}
You can also do what you are already trying to do, via reflection (but the performance will be very bad):
Type[] parsers =
{
typeof(PIC32MX_GCC_Parser),
typeof(M16C_IAR_Parser)
};
public Type findTheRightParser(string asmFileContents)
{
foreach(Type parser in parsers)
{
// You probably want to cache this
var mi = parser.GetMethod("isThisPlatform", BindingFlags.Static);
if ((Boolean)mi.Invoke(null, new object[] {asmFileContents}))
{
Console.WriteLine("Using parser: ", parser.platformName);
return parser;
}
}
return null;
}
You can't have static interfaces but you can get the behavior you are looking for if you switch to singletons that redirect to the static fields. Because you use a singleton and the singleton holds no data it has a very low memory overhead, only a few bytes per type.
public interface IParser
{
string platformName { get; }
bool isThisPlatform(string asmFileContents);
bool parseAsm(string asmFileContents);
}
class PIC32MX_GCC_Parser : IParser
{
private PIC32MX_GCC_Parser()
{
}
public static string platformName { get { return "PIC32MX_GCC"; } }
public static bool isThisPlatform(string asmFileContents)
{
return false; // stub
}
public static bool parseAsm(string asmFileContents)
{
return false; // stub
}
private static readonly PIC32MX_GCC_Parser _instance = new PIC32MX_GCC_Parser();
public static IParser Instance
{
get { return _instance; }
}
string IParser.platformName { get { return platformName; } }
bool IParser.isThisPlatform(string asmFileContents)
{
return isThisPlatform(asmFileContents);
}
bool IParser.parseAsm(string asmFileContents)
{
return parseAsm(asmFileContents);
}
}
class M16C_IAR_Parser : IParser
{
//..snip
}
Parser[] parsers =
{
PIC32MX_GCC_Parser.Instance,
M16C_IAR_Parser.Instance
};
public IParser findTheRightParser(string asmFileContents)
{
foreach (IParser parser in parsers)
{
if (parser.isThisPlatform(asmFileContents))
{
Console.WriteLine("Using parser: ", parser.platformName);
return parser;
}
}
return null;
}
However if this where me I would just drop the static methods and put all of the data right inside the singleton.
I am using the following methods:
public void M1(Int32 a)
{
// acquire MyMutex
DoSomething(a);
// release MyMutex
}
and
public void M2(String s, String t)
{
// acquire MyMutex
DoSomethingElse(s, t);
// release MyMutex
}
From what I have found so far it seems that it is not possible to use a single delegate for two methods with different signatures.
Are there any other alternatives to write something like this:
public void UsingMutex(...)
{
// acquire MyMutex
...
// release MyMutex
}
UsingMutex(M1);
UsingMutex(M2);
All I can think for the moment is to use two delegates and a boolean flag to know which delegate to call, but it is not a long term solution.
It is possible to combine generics with delegates? And if so, do you have some links for any kind of documentation?
Environment: C# 2.0
Absolutely you can mix delegates with generics. In 2.0, Predicate<T> etc are good examples of this, but you must have the same number of args. In this scenario, perhaps an option is to use captures to include the args in the delegate?
i.e.
public delegate void Action();
static void Main()
{
DoStuff(delegate {Foo(5);});
DoStuff(delegate {Bar("abc","def");});
}
static void DoStuff(Action action)
{
action();
}
static void Foo(int i)
{
Console.WriteLine(i);
}
static void Bar(string s, string t)
{
Console.WriteLine(s+t);
}
Note that Action is defined for you in .NET 3.5, but you can re-declare it for 2.0 purposes ;-p
Note that the anonymous method (delegate {...}) can also be parameterised:
static void Main()
{
DoStuff(delegate (string s) {Foo(5);});
DoStuff(delegate (string s) {Bar(s,"def");});
}
static void DoStuff(Action<string> action)
{
action("abc");
}
static void Foo(int i)
{
Console.WriteLine(i);
}
static void Bar(string s, string t)
{
Console.WriteLine(s+t);
}
Finally, C# 3.0 makes this all a lot easier and prettier with "lambdas", but that is another topic ;-p
Yes, it's possible to combine generics with delegates.
public delegate void Action<T>(T x);
public delegate void Action<T,U>(T x, U y);
public void UsingMutex<T>(Action<T> x, T t) {
// acquire mutex...
x(t);
// release mutex...
}
public void UsingMutex<T,U>(Action<T,U> x, T t, U u) {
// acquire mutex...
x(t, u);
// release mutex...
}
But you still have to handle different number of parameters using overloads.
If you look at the Func<T> and Action<T> delegates in the framework, you'll see that they define a number of similar delegates with different number of parameters. You can use generics, but that doesn't solve the number of arguments issue you're talking about.