How to make a WPF app not to overwrite the files it creates.

See more:

WPF

The program below creates a snapshot of itself by pressing the P key. It creates the file in the directory the program is in. For example the first time you press the P key it creates the file snapshot.png, if you press it again it creates snapshot_1, third time snapshot_2 and so on...

But if you close the program and start it again and those files are existing now in the directory, if now you press P key it overwrites them...

What I want is the program to check if the file that it tring to create exist, and if so, to try to create a file with the next number in the row.. and if that exist too, then try the next, and so on, untill it finds a file name that not exist and only then to create the file.

Can you guys help me modify the code to do what i'm describing?

Thanks

What I have tried:

    string filename = "\\screenshot.png";
    private void Mainwindow_KeyDown(object sender, KeyEventArgs e)
    {

        if (e.Key == Key.P)
        {

            FrameworkElement element = UxVisual as FrameworkElement;

            var pathstr = 

System.IO.Path.GetDirectoryName(System.Diagnostics.Process.GetCurrentProcess().MainModule.FileName);

            if (System.IO.File.Exists(pathstr + filename))
            {
                try
                {
                    string i = 
                    filename.Substring(filename.LastIndexOf('_') + 1, 
                    filename.LastIndexOf('.') - (filename.LastIndexOf('_') 
                    + 1));

                    filename = "\\screenshot_" + (Convert.ToInt32(i) +  
                    1).ToString() + ".png";
                }
                catch
                {
                    filename = "\\screenshot_1.png";
                }
            }
            Uri path = new Uri(pathstr + filename);


            CaptureScreen(element, path);
        }