C# Simple substitution cipher

decodeCaesar.cs

using System;
using System.Collections.Generic;
class DecodeCaesarTool {
		public static void Main(string[] args) {
				if(args.Length == 0 ) {
					Console.WriteLine("DecodeCaesar.exe <cipher text>");
				}else{
						for(int i = 1;i<26;i++) {
								List<char> r = DecodeCaesar(args[0],i);
								Console.WriteLine("seed:{0},{1}",i,new String(r.ToArray()));
						}
				}
		}

		private static List<char> DecodeCaesar(string chiher,int seed) {
				char[] alpha = "abcdefghijklmnopqrstuvwxyz".ToCharArray();
				List<char> list = new List<char>(alpha);
				List<char> result = new List<char>();
				char[] text = chiher.ToLower().ToCharArray();
				for(int i = 0;i<text.Length;i++) {
						if(!Char.IsNumber(text[i])) {
								if(25 >= (list.IndexOf(text[i]) + seed)) {
										result.Add(list[list.IndexOf(text[i]) + seed]);
								}else{
										result.Add(list[Math.Abs(seed - list.IndexOf(text[i]))]);
								}

						}else{
								continue;
						}
				}
				return result;
		}
}