How can I create the program that encrypts file with 2DES (doubleDES)?

I know doubleDES is not used sine of Meet-in-the-middle Attack but i need to create a program that does that kind of encryption. I tried this but i think im stuck and just cannot figure out what am i missing..

DESCryptoServiceProvider DES = new DESCryptoServiceProvider();

DES.Mode = CipherMode.ECB;
DES.Padding = PaddingMode.Zeros;
// *****ENKRIPTIMI*****
DES.Key = utf8.GetBytes(textBox1.Text.Substring(0, 8));
StreamReader sr = new StreamReader(textBox2.Text);
string permbajtja = sr.ReadToEnd();
sr.Close();
FileStream fs1 = new FileStream(textBox2.Text, FileMode.Create, FileAccess.Write);
CryptoStream cs = new CryptoStream(fs1, DES.CreateEncryptor(), CryptoStreamMode.Write);
StreamWriter sw = new StreamWriter(cs);
sw.Write(permbajtja); sw.Flush();
sw.Close();
StreamReader stream = new StreamReader(textBox2.Text);
string msg = stream.ReadToEnd();
stream.Close();
MessageBox.Show(msg);



//*****DEKRIPTIMI*****

DES.Key = utf8.GetBytes(textBox1.Text.Substring(8, 8));
FileStream fs2 = new FileStream(textBox2.Text, FileMode.Open, FileAccess.Read);
CryptoStream cs1 = new CryptoStream(fs2, DES.CreateDecryptor(), CryptoStreamMode.Read);
StreamReader sr1 = new StreamReader(cs1);
string permbajtja1 = sr1.ReadToEnd();
//    MessageBox.Show(permbajtja1);
sr1.Close();
fs2.Dispose();
fs2.Close();


StreamWriter sw1 = new StreamWriter(textBox2.Text);
sw1.Write(permbajtja1);
sw1.Flush();
sw1.Close();

**** THE PART ABOVE IS JUST FOR ENCRYPTING *****

The decryption part

DESCryptoServiceProvider DES = new DESCryptoServiceProvider();

DES.Mode = CipherMode.ECB;
DES.Padding = PaddingMode.Zeros;
// *****ENKRIPTIMI*****
DES.Key = utf8.GetBytes(textBox1.Text.Substring(8,8));
StreamReader sr = new StreamReader(textBox2.Text);
string permbajtja = sr.ReadToEnd();
sr.Close();
FileStream fs1 = new FileStream(textBox2.Text, FileMode.Create, FileAccess.Write);
CryptoStream cs = new CryptoStream(fs1, DES.CreateEncryptor(), CryptoStreamMode.Write);
StreamWriter sw = new StreamWriter(cs);
sw.Write(permbajtja); sw.Flush();
sw.Close();
StreamReader lexo = new StreamReader(textBox2.Text);
MessageBox.Show(lexo.ReadToEnd());
lexo.Close();

////*****DEKRIPTIMI*****

DES.Key = utf8.GetBytes(textBox1.Text.Substring(0, 8));
FileStream fs2 = new FileStream(textBox2.Text, FileMode.Open, FileAccess.Read);
CryptoStream cs1 = new CryptoStream(fs2, DES.CreateDecryptor(), CryptoStreamMode.Read);
StreamReader sr1 = new StreamReader(cs1);
string permbajtja1 = sr1.ReadToEnd();
MessageBox.Show(permbajtja1);
sr1.Close();
fs2.Dispose();
fs2.Close();


StreamWriter sw1 = new StreamWriter(textBox2.Text);
sw1.Write(permbajtja1);
sw1.Flush();
sw1.Close();