How to delete a text file when i close my windows form?

To delete the file, use File.Delete(string filepath) method.

You can use the Closed event, for that purpose:

If you have a FileStream and you want to close it when the form is closed, you can add an event-handler to the Closed event using the designer or, in the constructor of your form, like the following:

this.Closed += new EventHandler(Form1_Closed);

and implement the event-handler to close your file, like the following:

void Form1_Closed(object sender, EventArgs e)
{
    myFileStream.Close();
}

You can use File.Delete to delete the file on FormClosing[^] as Prasad said.

http://msdn.microsoft.com/en-us/library/system.io.file.delete.aspx[^]

use this code but make sure that the file is not used by any application

private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
  File.Delete( path + filename);
}

If, as Shmuel Zang suggests, you have a handle to this file (i.e. a FileStream, StreamWriter, TextWriter etc) open, you won't be able to delete it until after you close the handle. So in the Closed event you should do something like

FileStream fs; // let's say you have this
// if it's a StreamWriter etc the code is basically the same

void FormClosed(object sender, EventArgs e){
 fs.Close();
 
 File.Delete(filename);
}

Note that (contrary to some of the solutions above) you should use the FormClosed event for terminal tidy-up tasks like this, not FormClosing. FormClosing is called when a close request is received (i.e. the user presses Alt+F4, or code calls Close), and any handler attached to the form can reject it and cause the form not to be closed after all. FormClosed is called when the form has actually been closed, and there is no chance it won't be closed. That's the point where you want to clear things up which you've created during the course of the application. (Well, either there or in your Main method after the Application.Run.)