listbox items

//Directory where all the data files are kept
string sDirectory = @"D:\CSharpProject\MyData\";

private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    string sFilePath = sDirectory + listBox1.SelectedItem.ToString().Trim() + ".txt";
    LoadMyFile(sFilePath);
}

public void LoadMyFile(string filename)
{
    if (File.Exists(filename))
    {
        // Load the contents of the file into the RichTextBox.
        richTextBox1.LoadFile(filename, RichTextBoxStreamType.PlainText);
    }
    else
    {
        MessageBox.Show("File doesn't exist in the folder : " + sDirectory );
    }
}