There are two important windows forms methods that you will be using this week: a. To test if a string (such as the Text field of a textbox) is empty or null, use the string . IsNullOrEmpty (string ) method b. To pop up a MessageBox with a message and an OK button, use MessageBox . Show (message) 2. Open your course project solution from last week. It should look something like the screenshot below. 3. Revise the programming logic in the AddButton_Click event handler. Double-click on the "Add Song" button to bring up the code for the event handler. It should be similar to the code below