public class MD5Str
{
  /// <summary>
  /// 字符串MD5加密
  /// </summary>
  /// <param name="Text">要加密的字符串</param>
  /// <returns>密文</returns>
  public static string MD5(string Text)
  {
    byte[] buffer = System.Text.Encoding.Default.GetBytes(Text);
    try
    {
      System.Security.Cryptography.MD5CryptoServiceProvider check;
      check = new System.Security.Cryptography.MD5CryptoServiceProvider();
      byte[] somme = check.ComputeHash(buffer);
      string ret = "";
      foreach (byte a in somme)
      {
        if (a < 16)
          ret += "0" + a.ToString("X");
        else
          ret += a.ToString("X");
      }
      return ret.ToLower();
    }
    catch
    {
      throw;
    }
  }
}

static void Main(string[] args)
{
  string data = "123456789"; //要加密的數(shù)據(jù)
  string encodeStr = "";  //加密后文本
  encodeStr = MD5Str.MD5(data);
  Console.WriteLine("原文本：{0}", data);
  Console.WriteLine("加密后文本：{0}", encodeStr);
  Console.Read();
}