HOW to create an mdi interface 1.First create a new window form applcation. 2.Then set its form ISMDIcontainer property to true,This will make a form mdi container.whch is known as MDI PARENT. 3.ADD another form from solution explorer propertyTHIS WILL CREATE AN MDI CHILD. 4.After that add menu strip from tool box to both forms. 5.Now name component of your menu strip in first form as FILE ,window and in second form as new.AS shown in the images below 6.NOW add tool strip name to FILE as OPEN.AS shown in the images below 7.Now double-click on quotopenquot at form1 menustrip. 8.ADD the following Form2 obj new Form2 obj.MdiParent this obj.Show This code first create an object and then afterwords we use it to call diffrent method obj.MdiParentthis IT initialize Form2mdi child in form1mdi parent using this keyword which declares for a perticular instance. obj.show IT is a method that we use for a displaying form2mdi child. 9.Now run the application and see for yourself. 10.YOU can now add as many same codes to form2 to recreate same window application.