using overloading in calculator

sumaira you are only keeping track of a number when you click add (variable w) and on your = event you are taking the number currently being display on the textbox + w. Because of that you will only get the operation for the last number entered and current number on the textbox.

I would say to build an expression like first#+operation+second#+operitation...etc until the equals button is clicked and than you can evaluate your expression. If you don't want string parsing you can just keep a list of numbers, but keeping in mind concatenated operations.