Hello, this source code demonstrates how to create a basic calculator using Visual Basic.Net
This Calculator application can perform two tasks i.e Addition and Subtraction of whole numbers.

Global Variables

1. Dim
   
   operater_on As
   
   Boolean
   
   =
   
   False
   
2. Dim
   
   operater As
   
   String
   
   =
   
   ""
   
3. Dim
   
   val1, val2 As
   
   Double
   

Form Load Event

1. Private
   
   Sub
   
   Form1_Load(
   
   sender As
   
   Object
   
   , e As
   
   EventArgs)
   
   Handles
   
   MyBase
   
   .
   
   Load
   
2. AddHandler
   
   btn0.
   
   Click
   
   , AddressOf
   
   buttonClick
   
3. AddHandler
   
   btn1.
   
   Click
   
   , AddressOf
   
   buttonClick
   
4. AddHandler
   
   btn2.
   
   Click
   
   , AddressOf
   
   buttonClick
   
5. AddHandler
   
   btn3.
   
   Click
   
   , AddressOf
   
   buttonClick
   
6. AddHandler
   
   btn4.
   
   Click
   
   , AddressOf
   
   buttonClick
   
7. AddHandler
   
   btn5.
   
   Click
   
   , AddressOf
   
   buttonClick
   
8. AddHandler
   
   btn6.
   
   Click
   
   , AddressOf
   
   buttonClick
   
9. AddHandler
   
   btn7.
   
   Click
   
   , AddressOf
   
   buttonClick
   
10. AddHandler
    
    btn8.
    
    Click
    
    , AddressOf
    
    buttonClick
    
11. AddHandler
    
    btn9.
    
    Click
    
    , AddressOf
    
    buttonClick
    
12. End
    
    Sub
    

Number buttons click handler

1. Private
   
   Sub
   
   buttonClick(
   
   sender As
   
   Object
   
   , e As
   
   EventArgs)
   
2. 
   
3. Dim
   
   btn As
   
   Button =
   
   DirectCast
   
   (
   
   sender, System.
   
   Windows
   
   .
   
   Forms
   
   .
   
   Button
   
   )
   
4. If
   
   lblDisplay.
   
   Text
   
   =
   
   "0"
   
   Or
   
   operater_on =
   
   True
   
   Then
   
5. lblDisplay.
   
   Text
   
   =
   
   btn.
   
   Text
   
6. operater_on =
   
   False
   
7. Else
   
8. lblDisplay.
   
   Text
   
   =
   
   lblDisplay.
   
   Text
   
   &
   
   btn.
   
   Text
   
9. End
   
   If
   
10. End
    
    Sub
    

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