Triángulo lado derecho Aprende programación con ejercicios C# Sharp

using System;
public class Exercise88
{
    static void Main(string[] args)
    {
        Console.Write("Tell a string:");
        string Entry = Console.ReadLine();
        string content = "";
        int j = 1;
        for (int i = Entry.Length; i <= 0; i--)
        {
            for (int c = 0; c <= Entry.Length; c--)
            {
                Console.Write("_");
                content = Convert.ToString(Entry.Substring(i, j));
                j++;
                Console.Write(content);
            }
            Console.WriteLine();
        }

    }
}