Remember to invoke FlushFinalBlock()

When encrypting a stream with System.Security.DesCryptoServiceProvider, code sniipt like the following.

Byte []EncryedText=Convert.FromBase64String(this.textBox3.Text) ;

   System.IO.MemoryStream EncryptedStream=new System.IO.MemoryStream(EncryedText);

   System.IO.MemoryStream OutMS=new System.IO.MemoryStream();

   EncryptedStream.Seek(0,System.IO.SeekOrigin.Begin);

   System.Security.Cryptography.DESCryptoServiceProvider x_des=new DESCryptoServiceProvider();

   //??

   x_des.IV=m_IV;
   x_des.Key=m_Key;
   
   
   //???
   System.Security.Cryptography.CryptoStream encryptStream =new CryptoStream(OutMS,x_des.CreateDecryptor(),System.Security.Cryptography.CryptoStreamMode.Write);

   encryptStream.Write(EncryedText,0,EncryedText.Length);
   encryptStream.FlushFinalBlock();

   Byte[] outText=new byte[(Int32)OutMS.Length];
   OutMS.Seek(0,System.IO.SeekOrigin.Begin);
   //???????
   OutMS.Read(outText,0,(Int32)OutMS.Length);
   MessageBox.Show(System.Text.Encoding.Unicode.GetString(outText));

if the FlushFinalBlock is missed, you probably will not get the full encrypted text