C# How to use GetMethod to find a specific overload with a generic out parameter?

问题

Everything is in the title, but let me put some code. Let's say we have a class with 2 methods with the same name:

class MyClass
{
  /// <summary>
  /// The first version
  /// </summary>
  public TItem Foo(long param1) { ... }
  /// <summary>
  /// Overload with a generic parameters
  /// </summary>
  public bool Foo<TItem>(out TItem item, long param1) { ... }
}

An we need to get the MethodInfo for the second 'Foo' method which has a generic out parameter:

    public class AnotherClass
    {
      public MethodInfo GetFooForType(Type typeOfItem)
      {
        // the answer is probably GetMethod with the right parameters
        return typeof(MyClass).GetMethod(???);
      }
    }

Please note that:

I'm trying to NOT USE GetMethods or GetMember because it's inelegant and prone-to-future-errors
Renaming any of the Foo methods is not an option (would be too easy).
The type or TItem is obviously known only at runtime.
I'm probably looking for the right parameters for GetMethod, but I can take any suggestion (other that GetMethods or GetMember).
I spent 1 hour searching StackOverflow for the answer without success, but reflection evolved so much that there is a lot of irrelevant answers all around. Adding a date filter in stackoverflow might be a great idea (or maybe a .Net framework version filter ?)
You are more than welcome to prove me wrong an find me the obvious answer I missed !
This is not a .Net Core project (MakeGenericMethodParameter is not an option)
My name is Mose and I'm a bullet addict ^^

回答1:

If your class is a generic one (and if it is not, your code will give you a warning about overriding) you can use typeof(MyClass<>).GetGenericArguments().First().MakeByRefType():

class MyClass<TItem>
{
    /// <summary>
    /// The first version
    /// </summary>
    public TItem Foo(long param1) { throw new Exception(); }
    /// <summary>
    /// Overload with a generic parameters
    /// </summary>
    public bool Foo(out TItem item, long param1) { throw new Exception();}
}

var genericMI = typeof(MyClass<>).GetMethod(
    "Foo",
    new[] 
    { 
         typeof(MyClass<>).GetGenericArguments().First().MakeByRefType(), 
         typeof(long)
    });

For non-generic you can use Type.MakeGenericMethodParameter(0).MakeByRefType() (actually it will work with MyClass<T> and override of generic parameter in Foo<T> too):

class MyClass
{
    /// <summary>
    /// The first version
    /// </summary>
    public int Foo(long param1) { throw new Exception(); }
    /// <summary>
    /// Overload with a generic parameters
    /// </summary>
    public bool Foo<TItem>(out TItem item, long param1) { throw new Exception();}
}

var genericMI = typeof(MyClass).GetMethod(
        "Foo",
        new[] 
        {
            Type.MakeGenericMethodParameter(0).MakeByRefType(),
            typeof(long)
        });

来源：https://stackoverflow.com/questions/61879161/c-sharp-how-to-use-getmethod-to-find-a-specific-overload-with-a-generic-out-para

标签

generics

reflection

getmethod