如何在C＃中使用表示反射结果类型的变量进行转换.Invoke（）

Question

I have a method that returns byte[] but for now would like to avoid using generics on the method to supply the return type. I currently pass a parameter into this method that has the details of the type of the data that will be serialized to the byte[] return result.

Question:

How do I perform a dynamic cast of the result of .Invoke() ?

I'm using reflection to call a method on a class the output of this is object and this result needs to be cast.

The Code:

public byte[] SomeMethod(/* some params */)
{
    MethodInfo info = /* ... */ .GetMethod(methodToCall);

    //Here I want to perform a dynamic cast:
    return (info.Invoke(classToCall, methodParams)).Serialize();

    //if I was to just have the method fixed to a type it would look like:
    return (info.Invoke(classToCall, methodParams) as SomeType).Serialize();

    //NOTE: .Serialize() is just my own extension method
}

What I have tried without success:

//with returnType as a string
var dynamicType = Type.GetType(returnType);

(info.Invoke(classToCall, methodParams) as dynamicType).Serialize();

Also some other variations with typeof() , GetTypeHandle , .ReflectedType

---

Am I missing something simple and/or obvious, or am I just trying to do something strange/silly?

Additional note: the SomeMethod is an override of a method of a class hence not wanting to have the method support a generic type.

Answer 1

It is a common misunderstanding that the cast operator really does anything in this situation. You either want to convert from the type that Invoke returned to another type, or it already is the type you want it to be even though Invoke is declared to return object .

Since I don't think you want to convert anything, you have to first recognize that the return value of calling Invoke like this:

var result = info.Invoke(classToCall, methodParams);

the result will be a variable of type object but the value in that variable will already be the type you want to cast it to . You just don't know exactly what it is. And you need to know what it is to call Serialize .

Now, you have this extension method, or set of overloaded extension methods that operate on a compile time specified initial this parameter. One of them matches the type of the return value of the Invoke call.

In order to choose which of these methods to call, you need to use reflection again to get a MethodInfo matching the right type and just call your Serialize method. It might help if it weren't an extension method because now you have no easy way to look up the extension method the same way the compiler does at compile time only. Extension method matching is extremely laborious and not suited to dynamic invocation.

Instead, if you want to use reflection a second time to call Serialize , without having a giant switch statement, then you need to have a utility class with all the Serialize methods as public overloads within that class. At least that is one way to approach the problem.

Answer 2

2 methods come to mind if you don't want to use generics.

First method would be to cast based on methodToCall. Not too elegant.

if (methodToCall == "method1")
  return ((obj1)info.Invoke(classToCall, methodParams)).Serialize();
else if (methodToCall == "method2")
 return ((obj2)info.Invoke(classToCall, methodParams)).Serialize();

Second method would be to create a super class that is inherited by all possible return types of your methodToCall. The super class would have .Serialize() declared and inherited by the sub classes.

interface mySuperClass
{
  byte[] Serialize();
}

Cast as mySuperClass

return (info.Invoke(classToCall, methodParams) as mySuperclass).Serialize();

This may not work too well if you have a very large number of possible return types. Happy coding.