Adding / Deleting Controls at Run Time in VB

Image via Wikipedia

Hello all, and welcome to my first official VB Wednesday! *doot-da-doo*

Today, I’ll discuss how to add and remove controls (buttons and picture boxes) on a form during runtime in VB.

What is run time?  Run time is the time when code is running on a computer.  Normally, you would add controls during development time, when you are designing the program.

Sometimes, though, the need arises to create controls at run time.  The most common reason for this would be a login scenario.  The user logs in on the sidebar, and extra content shows up on the page.

For purpose of example, I have created a little demo of this method.  Though it isn’t a login scenario (I didn’t think of that until I wrote it ), it should give you a good idea of how to use this technique.

You can download the demo here.  For the executable, unzip the file, and go to ButtonGame\bin\Debug and run ButtonGame.exe.

Now, open up the code and look at the source for ButtonGame.vb.  On lines 12- 22, you’ll see the following code:

     
     Dim NewButton As New Button()
     Me.Controls.Add(NewButton)     
     If nBackColor <> Nothing Then
          NewButton.BackColor = nBackColor
     End If     
     NewButton.Height = nHeight
     NewButton.Text = "I'm a button!"
     NewButton.Width = 115
     NewButton.Location = New Point(r.Next(525), r.Next(430))

What happens here?  Well, on line 12, we create a button.   At this point, the button is just an abstract identity;  it’s not actually on the form.  Then on line 13, we add it to Me.Controls. This is a very important variable that stores a list of all controls on a form.  You may have seen it used for parsing controls before.  Here, we add our button, thus adding it to the form.  Pretty nifty, eh?

Now, glance down to lines 42 – 50.

       For x = 1 To 100
            For Each c As Control In Me.Controls
                If TypeOf c Is Button Or TypeOf c Is PictureBox Then
                    If Not c.Name.StartsWith("saveme") Then
                        Me.Controls.Remove(c)
                    End If
                End If
            Next
        Next

What happens here is that we parse all of the controls on the form.  We then use an If statement to restrict the parsing to only Buttons and PictureBoxes (the bunny button produces these).  If the name of the control does not indicate that it should be kept from deletion, we remove it from the form by taking it out of Me.Controls.

So, that’s how to add and remove controls from a form during runtime.  It may be simple, but it is also helpful.

I’ll see you on Friday!  If you have any funny computer-related jokes/pics, then please send them in! Do pobachennya (that’s Ukrainian for good bye)!

Related articles

• Programming VB.NET (docserve.wordpress.com)
• Making a DrawImage a button in VB.net 2010 (stackoverflow.com)

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