C#: Call non-generic method from generic method

Question

class CustomClass<T> where T: bool
{
    public CustomClass(T defaultValue)
    {
        init(defaultValue); // why can't the compiler just use void init(bool) here?
    }
    public void init(bool defaultValue)
    {

    }
    // public void init(int defaultValue) will be implemented later
}

Hello. This seems to be a simple question, but I couldn't find an answer on the Internet: Why won't the compiler use the init method? I simply want to provide different methods for different types.

Instead it prints the following error message: "The best overloaded method match for 'CustomClass.init(bool)' has some invalid arguments"

I would be glad about a hint.

Best regards, Chris

Answer 1

The compiler cannot use init(bool) because at compile-time it cannot know that T is bool. What you are asking for is dynamic dispatch — which method is actually being called depends on the run-time type of the argument and cannot be determined at compile-time.

You can achieve this in C# 4.0 by using the dynamic type:

class CustomClass<T>
{
    public CustomClass(T defaultValue)
    {
        init((dynamic)defaultValue);
    }
    private void init(bool defaultValue) { Console.WriteLine("bool"); }
    private void init(int defaultValue) { Console.WriteLine("int"); }
    private void init(object defaultValue) {
        Console.WriteLine("fallback for all other types that don’t have "+
                          "a more specific init()");
    }
}