Question

I push a button and a list all the files in my given path appears in a listbox.

        IEnumerable<string> files = System.IO.Directory.EnumerateFiles(@"C:\Desktop\Stuffs\Dummi", "*.*", System.IO.SearchOption.AllDirectories);
        foreach (var f in files)
        {

            lbz.Items.Add(String.Format("{0}", f)); 

I want to be able to select a file from the list and open it’s contents in a text box below the listbox.

Answer 1

SteveDog’s answer should work fine for small files.

If you have large files, this may lock up the UI as the file’s contents are read. In that case you could use a BackgroundWorker to read the file:

ListBox lbz;
TextBox tbx;
BackgroundWorker bgw;

void lbz_SelectedIndexChanged(object sender, EventArgs e)
{
    if (!bgw.IsBusy)
    {
        bgw.RunWorkerAsync(lbz.SelectedItem.ToString());
    }
}

void bgw_DoWork(object sender, DoWorkEventArgs e)
{
    e.Result = File.ReadAllText((string)e.Argument);
}

void bgw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
    tbx.Text = (string)e.Result;
}