CODEWITHSUNDEEP
c#.netreflectionreflection.emit
Qwertie
Qwertie

Reputation: 17186

Reflection.Emit: How to convert MethodBuilder to RuntimeMethodInfo reliably?

After generating a type dynamically and calling TypeBuilder.CreateType, I want to create a delegate that points to a method in the new type. But if I use code like

loadedType = typeBuilder.CreateType();
myDelegate = (MyDelegate)Delegate.CreateDelegate(
                                  typeof(MyDelegate), methodBuilder);

Reusing the methodBuilder as a methodInfo, I get the exception "MethodInfo must be a RuntimeMethodInfo". Now normally I can re-acquire the MethodInfo with

MethodInfo mi = loadedType.GetMethod(methodBuilder.Name);
myDelegate = (MyDelegate)Delegate.CreateDelegate(typeof(MyDelegate), mi);

But my class may contain several overloaded methods with the same name. How do I make sure I get the right one? Do methods have some persistent identifier I could look up in loadedType?

Update: okay, here's what I'm using to re-acquire the MethodInfo. I just wish I could be sure it works in all cases.

private static MethodInfo ReacquireMethod(Type type, MethodInfo method)
{
    BindingFlags flags = BindingFlags.DeclaredOnly;
    flags |= (method.IsPublic ? BindingFlags.Public : BindingFlags.NonPublic);
    flags |= (method.IsStatic ? BindingFlags.Static : BindingFlags.Instance);
    MethodInfo m = type.GetMethod(method.Name, flags, null,
                                          ParameterTypes(method), null);
    Debug.Assert(m != null);
    return m;
}

Upvotes: 3

Views: 3270

Answers (2)

LukeH
LukeH

Reputation: 269428

As far as I'm aware there's no persistent shared identifier.

Overloads of a method are distinguished by their parameter lists, so my guess is that you'll need to call GetParameters on methodBuilder and then translate the returned ParameterInfo[] array into a Type[] array to pass to the the appropriate GetMethod overload:

MethodInfo mi = loadedType.GetMethod(
    methodBuilder.Name,
    methodBuilder.GetParameters().Select(p => p.ParameterType).ToArray());

Upvotes: 3

jrista
jrista

Reputation: 32960

You need to use the GetMethod overload that takes an array of types. Method overloads are selected for binding by the parameters passed to them. Since you are not actually calling a method when getting their metadata via reflection, you have to provide an ordered array of Type objects to get the right MethodInfo object:

Type.GetMethod Method (String, Type[])

Used like:

MethodInfo mi = loadedType.GetMethod(
    methodBuilder.Name, 
    new[] 
    { 
        typeof(string), 
        typeof(int) 
    }
);

Assiming methodBuilder.Name is "MyMethod", that would bind the following:

public <returnType> MyMethod(string param1, int param2);

Remember that the return type is not a part of a method signature, only the method name and its parameter types are.

Upvotes: 0

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