C# Reflection on this-Object

Question

i totaly got stuck in a Reflection Problem, i think it isn't real big, but i don't find any solution for this.

public class myClass : myClassIF {

    public myClass() { }

    private void doSomething_A() {
        //...
    }

    private void doSomething_B() {
        //...
    }

    public void DecideAndCall(string identifier) {
        string methodName = "doSomething_" + identifier;
        MethodInfo mi = this.GetType().GetMethod(methodName); //here i got a NullReference??
        //here should be the Invocation of the Method and so on...
    }
}

The Interface looks this way:

public interface myClassIF {

    void DecideAndCall(string identifier);

}

If i call the GetMethod("...")-Method, i always got a NullReference. I can't understand this, because in an other Part of this Project i've done this before. But there i used Refelction to an other Type not to "this".

Is it possible to Reflect Methods in the actually instanciated Object? I think i'd should be, but i don't know how...

Many Thanks! Benni

Answer 1

The method you want to retrieve is private, but the parameterless Type.GetMethod method only looks for public methods. Try the overload that lets you specify binding-constraints:

BindingFlags flags = BindingFlags.Instance | BindingFlags.NonPublic;
MethodInfo mi = GetType().GetMethod(methodName, flags);

I would strongly recommend against doing something like this though. It's highly unusual for an object to perform reflection on itself . You obviously lose type-safety; for example, your provided sample will fail spectacularly if the argument to the method is something other than "A" or "B" . Although I'm sure your real program is more complicated, are you sure you can't redesign this in a way that doesn't require reflection?

Answer 2

The methods you're interested in are private, so you'll need to specify BindingFlags.NonPublic in your arguments:

public void DecideAndCall(string identifier)
{
    string methodName = "doSomething_" + identifier;

    BindingFlags flags = BindingFlags.Instance | BindingFlags.NonPublic;
    MethodInfo mi = this.GetType().GetMethod(methodName, flags);
    // ...
}

Answer 3

你需要使用BindingFlags.NonPublic来获取私有方法。

Answer 4

Since the methods are private, you need to use the overload taking BindingFlags

MethodInfo mi = typeof(myClass).GetMethod(methodName, BindingFlags.Instance | BindingFlags.NonPublic); 

This is discussed in more detail here