Decrypting multiple text files and storing in multiple text

Question

 I have a program given below. I wanna process multiple text file at once and display the result in different text file.

Please help.

 

namespace TMSDescriptionSample

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private void button1_Click(object sender, EventArgs e)

{

string error = "";

string encryptedText = File.ReadAllText(AppDomain.CurrentDomain.BaseDirectory + "input.txt");

string decryptedText = TMSDecryptionAPI.DecryptString(encryptedText, ref error); //pass the encrypted text to this function and it will return the decrypted text.

File.WriteAllText(AppDomain.CurrentDomain.BaseDirectory + "ouput.txt", decryptedText);

MessageBox.Show("Done");

}

}

}