private string createHash(string strSource)
{
   Byte[] bytSource; // will hold Unicode bytes of source string
   Byte[] bytHash;   // will hold bytes of encrypted (hash) string

   System.Text.UnicodeEncoding unicodeConverter = 
      new System.Text.UnicodeEncoding();

   System.Security.Cryptography.SHA256Managed shaEncrypter = 
      new System.Security.Cryptography.SHA256Managed();

   // fill array with Unicode chars from source string
   bytSource = unicodeConverter.GetBytes(strSource);

   bytHash = shaEncrypter.ComputeHash(bytSource); // encrypt the byte array

   return Convert.ToBase64String(bytHash); // return Base64 string
}