Just filling in some default fields in the tio editor would do. For example pre-fill the header as:

   using System;
   using System.IO;

and pre-filling Code with

   namespace example
   {
      public class Example
      {
         static void Main(){
         }
      }
   }

(But better names, my naming sucks!)

That would go a long way, then you could just add "Console.WriteLine("Hello World"); for hello world.