Question

I know what’s wrong, I don’t know how to fix it.

I get a

NullReferenceException: Object reference not set to an instance of an object.

I get this error because I have a populated ListBox, when you select a file name in the ListBox the contents of that file are then displayed in a textbox.

Now, I have a depopulate button that clears all the files from the ListBox, if a file is selected, then I get the error.

I want to be able to click the depopulate button and clear both boxes.

The code:

private void DE_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    myScaleTransform2.ScaleX = myScaleTransform2.ScaleX * .9833333333333333333333333333333333333333333333333333333333;
    myScaleTransform2.ScaleY = myScaleTransform2.ScaleY * .9833333333333333333333333333333333333333333333333333333333;
    lbz.Items.Clear();
}

private void lbz_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    tb1.Text = File.ReadAllText(lbz.SelectedItem.ToString());
}

Answer 1

private void lbz_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
    if( lbz.SelectedItem != null ){
        if(File.Exist(lbz.SelectedItem.ToString())){
            tb1.Text = File.ReadAllText(lbz.SelectedItem.ToString());
        }
        else
        {
            tb1.Text = "File is not exist in the selected Path";
        }
    } else {
        tb1.Text = "No File Selected";
    }
}

Please check weather your list item contain file path or not?