Generic method and converting: how to define that Type 1 is convertible to Type 2

Question

I defined this method:

public static List<T2> ConvertList<T1, T2>(List<T1> param) where T1:class where T2:class
{
    List<T2> result = new List<T2>();

    foreach (T1 p in param)
        result.Add((T2)p);

    return result;
}

For converting Lists of Type 1 to Lists of Type 2.

Unfortunately I forgot, that C# compiler cannot say at this stage that T1 is convertible to T2, so it throws error:

error CS0030: Cannot convert type T1 to T2

Can someone direct me how to do it properly? I need this method for now only to convert list of custom class to list of object, so as in .NET everything derives from object it should work.

Basically what I would expect is some syntax to tell compiler that T2 (object) is base for T1 (MyClass), so something like:

public static List<T2> ConvertList<T1, T2>(List<T1> param) where T2: base of T1

(... where T2: base of T1)

Answer 1

You could specify it in a generic parameter:

public static List<T2> ConvertList<T1, T2>(List<T1> param) 
                 where T1:class,T2 
                 where T2:class
{
    List<T2> result = new List<T2>();

    foreach (T1 p in param)
        result.Add((T2)p);

    return result;
}