Let’s begin working on the sample application by creating an MDI parent form, which will contain the other forms in the application as well as common menu items:
Start by creating a new Windows Application project. Name the project MDIDemo.
Click Form1.vb in the Solution Explorer window; then change its File Name property in the Properties window to frmParent.vb.
Right-click the form’s Designer window, and then select View Code from the context menu. Rename the form by changing Public Class Form1 at the top of the Code window to Public Class frmParent. (It is possible that the name of the class was changed for you when you changed the File Name property in the previous step.)