public delegate TResult Func<in T, out TResult>(T arg)
public delegate TResult Func<in T1, in T2, out TResult>(T1 arg1, T2 arg2)
public delegate TResult Func<in T1, in T2, in T3, out TResult>(T1 arg1, T2 arg2, T3 arg3)
public delegate TResult Func<in T1, in T2, in T3, in T4...