private void btnLoad_Click(object sender, System.EventArgs e) 
{
           //Open fle dialog control used
            odlgSourceFile.InitialDirectory = @"C:\";

            // The file could be of any type. The Filter is restricted to Text Format 
            // files only for demonstration purposes.

            odlgSourceFile.Filter = "Text Format (*.txt)|*.txt";
            odlgSourceFile.FilterIndex = 1;

            // The OpenFileDialog control only has an Open button, not an OK button.
            // However, there is no DialogResult.Open enum so use DialogResult.OK.

            if (odlgSourceFile.ShowDialog() == DialogResult.OK) {
                try 
               {
                    txtCrypto.Text = ReadFileAsstring(odlgSourceFile.FileName);
                    strSourcePath = odlgSourceFile.FileName;
               } 
                catch( ArgumentException exp)
                {
                    MessageBox.Show(exp.Message, this.Text,MessageBoxButtons.OK, MessageBoxIcon.Warning);
                }
            }
    }

private void EncryptDecrypt_Click(object sender, System.EventArgs e) 
{	
        Button btn = (Button) sender;
        try 
         {
            crpSample.SourceFileName = strSourcePath;
			if (btn.Name == "btnEncrypt") 
			{
				crpSample.EncryptFile();
			}
			else 
			{
				crpSample.DecryptFile();
			}

            txtCrypto.Text = ReadFileAsstring(strSourcePath);
           } 
           catch(CryptographicException expCrypto)
           {
            MessageBox.Show("The file could not be decrypted. Make sure you entered " + 
                "the correct password. " + Environment.NewLine + "This error can also be caused by changing " + 
                "crypto type between encryption and decryption.", 
                this.Text,MessageBoxButtons.OK, MessageBoxIcon.Warning);
            }
            catch( Exception exp)
            {
            MessageBox.Show(exp.Message, this.Text,MessageBoxButtons.OK, MessageBoxIcon.Warning);
             }
}

public void EncryptFile()
{    
        // Create a FileStream object to read in the source file.
        FileStream fsInput = new FileStream(strSourceFile, FileMode.Open, FileAccess.Read);
        // Create a byte array from the FileStream object by reading in the source file.

        byte[] abytInput = new byte[Convert.ToInt32(fsInput.Length)];
        fsInput.Read(abytInput, 0, Convert.ToInt32(fsInput.Length));
        fsInput.Close();

        // Create a FileStream object to write to a temp file.

        FileStream fsCipherText = new FileStream("temp.dat", FileMode.Create, FileAccess.Write);
        fsCipherText.SetLength(0);

        // Create a Crypto Stream that transforms the file stream using the chosen 
        // encryption and writes it to the output FileStream object.

        CryptoStream csEncrypted = new CryptoStream(fsCipherText, crpSym.CreateEncryptor(), 
            CryptoStreamMode.Write);
        csEncrypted.Write(abytInput, 0, abytInput.Length);
       csEncrypted.FlushFinalBlock();
        // Clean up. There is no need to call fsCipherText.Close() because closing the
        // crypto stream automatically encloses the stream that was passed into it.
        csEncrypted.Close();
}

public void DecryptFile()
{   
        // Create a FileStream object to read back the encrypted file.
        FileStream fsCipherText = new FileStream(strSourceFile, FileMode.Open, FileAccess.Read);
        // Create a FileStream object to write to the temp file.
        FileStream fsPlainText = new FileStream("temp.dat", FileMode.Create, FileAccess.Write);
        // Read in the encrypted file and decrypt.
        CryptoStream csDecrypted = new CryptoStream(fsCipherText, crpSym.CreateDecryptor(), 
        CryptoStreamMode.Read);
        // Create a StreamWriter to write to the temp file.
        StreamWriter swWriter = new StreamWriter(fsPlainText);
        // Read the decrypted stream into a StreamReader.
        StreamReader srReader = new StreamReader(csDecrypted);
         try 
         {
	// Write out the decrypted stream.
	swWriter.Write(srReader.ReadToEnd());
          } 
          catch( CryptographicException expCrypto)
          {
	throw new CryptographicException();
           }
           finally
           {
            // Close and clean up.
            swWriter.Close();
            csDecrypted.Close();
           }
 }