VB.NET 2005 Daily Lesson [7.02.07] - Custom Controls Pt.1

ccoonen · #1 (**permalink**) 07-02-2007, 08:28 PM

Many times we want to stylize our form elements but modifying the properties of each form element can only take us so far. In many cases, their is also a need to make a control act in a certain way, but should only be changed once and reflected application-wide. I'll discuss a few ways you can make your OWN controls or extend the current controls for the features and functionality you actually deserve

User controls can be created with whatever elements you like. They can be added by right-clicking the project, and adding a new user control. At this point you are a blank slate, and you can add whatever elements (including other user controls) to your user control. You can even add your own properties which are then viewed and executed real time when you add the to a form. It's pretty cool when you "compile" and you see your own custom control in the toolbar

For example, Create a user control, add 5 textboxes and add this to the code of the User Control.

Code:

Public Class UserControl1

    Private _TextboxBackgroundColor As Color

    Public Property TextBoxBackgroundColor() As Color
        Get
            Return _TextboxBackgroundColor
        End Get
        Set(ByVal value As Color)
            _TextboxBackgroundColor = value
            TextBox1.BackColor = value
            TextBox2.BackColor = value
            TextBox3.BackColor = value
            TextBox4.BackColor = value
            TextBox5.BackColor = value
        End Set
    End Property

End Class

Then hit the compile button and watch how it now appears in your toolbar. Drag your new user control onto a form and notice in your properties window that you have available "TextBoxBackgroundColor" property now. Modify it and see that all 5 textboxes change for the control... Now, you are probably asking why would we do this (besides being freekin sweet). Because it extracts the control and now you can use this control everywhere. When the client decides that only 4 of the 5 textboxes should have that color... then it is only one change and it occurs application-wide.

The next lessons to come will discuss the ability to override controls using their events and how to inherit the already-built controls to make shnazzy looking form controls

HelloWorld · #2 (**permalink**) 07-02-2007, 09:25 PM

I personally kind of confused with Visual Basic whether this is the VB.NET or not, I'm not sure but I'm confused to both haha... Can you please describe it what happened on each lines?

I think the "As Color" is the Inheritance right? I'm not sure with the followings:
- Get
- Set
are those try catch blocks? no right? What is _TextBackgroundColor for?

ccoonen · #3 (**permalink**) 07-03-2007, 05:48 AM

Yes, in VB, getters/setters and called Properties. The Private variable holds the data for color value, the Get returns the private variable, and the Set actually sets the the private variable. We also hook into setting other control properties in our set... so when you set the Property "TextBoxBackgroundColor" to Color.Red for example, it will set all 5 controls and the internal variable so you could retrieve it again later. This way it is realtime in the VisualStudio GUI and you can use the properties in the properties window to see your changes instantly

_TextBackgroundColor is my own variable... showing you can extend these user controls to anything you want...

HelloWorld · #4 (**permalink**) 07-03-2007, 09:11 AM

Quote:

the Get returns the private variable

why do we need to Get the returns of the private variables? if we want to acccess them, can't we just call it...?

ccoonen · #5 (**permalink**) 07-03-2007, 11:15 AM

This is the hook if you ever wanted to retrieve the value that you've set. Say you wanted all form elements to use the same background color that you set your user control. You could set the color of your user control to red, enumerate over all other controls on the form, and "Set" their background color from the "Get" of your User control.

In all reality, if you wanted to limit it to "Set Only" you could change it the property to WriteOnly but then your loosing the ability to get the value realtime.

Code:

Public Class UserControl1
    Public WriteOnly Property TextBoxBackgroundColor() As Color
        Set(ByVal value As Color)
            TextBox1.BackColor = value
            TextBox2.BackColor = value
            TextBox3.BackColor = value
            TextBox4.BackColor = value
            TextBox5.BackColor = value
        End Set
    End Property
End Class

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