public delegate void Callback<T, U, V, W>(T arg1, U arg2, V arg3, W arg4);
public delegate void Callback<T, U, V, W, X>(T arg1, U arg2, V arg3, W arg4, X arg5);
public delegate void Callback<T, U, V, W, X, Y>(T arg1, U arg2, V arg3, W arg4, X arg5, Y arg6);