从实现IDictionary <，>的类型中获取类型参数

Question

I would like to write a function to get the type parameters from types implementing IDictionary. What I have so far, and what is discussed in most SO questions is:

public static Type[] GetParameters(Type dicType) {

    if (typeof(IDictionary).IsAssignableFrom(dicType)) {
        return dicType.GetGenericArguments();
    }
    else {
        return null;
    }
}

However this fails with the following:

public class MyClass : Dictionary<string, int> { }

Type[] typeParams = GetParameters(typeof(MyClass));
Console.WriteLine(String.Join(", ", (object[]) typeParams));

which would print nothing (empty array). This is even worse with the following:

public class MyOtherClass<T, U> : Dictionary<string, string> { }

Type[] typeParams = GetParameters(typeof(MyOtherClass<int, int>));
Console.WriteLine(String.Join(", ", (object[]) typeParams));

as the output is completely wrong (System.Int32, System.Int32).

How can I get these parameters for any type that inherits from IDictionary ?

Answer 1

While writing the question, I actually came up with an answer:

public static Type[] GetDictionaryParameters(Type dicType) {
    foreach(var interf in dicType.GetInterfaces()) {
        if (interf.IsGenericType && interf.GetGenericTypeDefinition() == typeof(IDictionary<,>)) {
            return interf.GetGenericArguments();
        }
    }

    // No matching interface
    return null;
}

This works with everything I have so far. If you have a better idea, please post another answer !