Random number string between 1 and 50

[code=c#]
using System;
using System.Collections.Generic;
using System.Text;
using System.Windows.Forms;

namespace daniweb
{
  public partial class frmRandom : Form
  {
    public frmRandom()
    {
      InitializeComponent();
    }

    public static int GetRandom(int Maxvalue)
    {
      byte[] randomNumber = new byte[1];
      System.Security.Cryptography.RNGCryptoServiceProvider Gen = new System.Security.Cryptography.RNGCryptoServiceProvider();
      Gen.GetBytes(randomNumber);
      int rand = Convert.ToInt32(randomNumber[0]);
      return rand % Maxvalue + 1;
    }

    public static string GetRandomNumberString()
    {
      List<int> lst = new List<int>();
      for (int i1 = 1; i1 <= 50; i1++)
        lst.Add(i1);
      
      StringBuilder result = new StringBuilder();
      while (lst.Count > 0)
      {
        int rnd = lst[GetRandom(lst.Count)-1];
        lst.Remove(rnd);
        result.Append(rnd.ToString("F0"));
        if (lst.Count > 0)
          result.Append(" ");
      }

      return result.ToString(); ;
    }

    private void button1_Click(object sender, EventArgs e)
    {
      string rnd = GetRandomNumberString();
      string[] sTest = rnd.Split(new char[] { ' ' });
      if (sTest.Length != 50)
        System.Diagnostics.Debugger.Break(); //Makes sure we have 50 elements
      Console.WriteLine(rnd);
    }
  }
}
[/code]