Radio Button Control in VB.NET
A RadioButton control provides a round interface to select one
option from a number of options. Radio buttons are usually placed in a group on
a container control such as a Panel or a GroupBox and one of them is selected.
Creating a RadioButton
We
can create a RadioButton control using a Forms designer at design-time or using
the RadioButton class in code at run-time (also known as dynamically).
To
create a RadioButton control at design-time, you simply drag and drop a RadioButton
control from Toolbox to a Form in Visual Studio. After you drag and drop a RadioButton
on a Form, the RadioButton looks like Figure 1. Once a RadioButton is on the
Form, you can move it around and resize it using mouse and set its properties
and events.
Figure 1
Creating a RadioButton control at run-time is merely work of
creating an instance of RadioButton class, set its properties and add RadioButton
class to the Form controls.
First step to create a dynamic RadioButton is to create an
instance of RadioButton class. The following code snippet creates a RadioButton
control object.
Dim dynamicRadioButton As New RadioButton()
In the next step, you may set properties of a RadioButton
control. The following code snippet sets location, width, height, background
color, foreground color, Text, Name, and Font properties of a RadioButton.
dynamicRadioButton.Left = 20
dynamicRadioButton.Top = 100
dynamicRadioButton.Width = 300
dynamicRadioButton.Height = 30
dynamicRadioButton.BackColor = Color.Orange
dynamicRadioButton.ForeColor = Color.Black
dynamicRadioButton.Text = "I
am a Dynamic RadioButton"
dynamicRadioButton.Name = "DynamicRadioButton"
dynamicRadioButton.Font = New
Font("Georgia",
12)
Once a RadioButton
control is ready with its properties, next step is to add the RadioButton
control to the Form. To do so, we use Form.Controls.Add method. The following
code snippet adds a RadioButton control to the current Form.
Controls.Add(dynamicRadioButton)
New RadioButton created
by the above code looks like Figure 2.
Figure 2
Setting RadioButton
Properties
After you place a RadioButton control on a Form, the next step is
to set properties.
The easiest way to set properties is from the Properties Window.
You can open Properties window by pressing F4 or right click on a control and
select Properties menu item. The Properties window looks like Figure 3.
Figure 3
Location,
Height, Width, and Size
The Location property takes a Point that specifies the
starting position of the RadioButton on a Form. You may also use Left and Top
properties to specify the location of a control from the left top corner of the
Form. The Size property specifies the
size of the control. We can also use Width and Height property instead of Size
property. The following code snippet sets Location, Width, and Height
properties of a RadioButton control.
dynamicRadioButton.Location = New Point(20, 150)
dynamicRadioButton.Height = 40
dynamicRadioButton.Width = 300
Background,
Foreground, BorderStyle
BackColor and ForeColor properties are used to set background and
foreground color of a RadioButton respectively. If you click on these
properties in Properties window, the Color Dialog pops up.
Alternatively, you can set background and foreground colors at
run-time. The following code snippet sets BackColor and ForeColor properties.
dynamicRadioButton.BackColor = Color.Red
dynamicRadioButton.ForeColor = Color.Blue
Name
Name property represents a unique name of a RadioButton
control. It is used to access the control in the code. The following code
snippet sets and gets the name and text of a RadioButton control.
dynamicRadioButton.Name = "DynamicRadioButton"
Text and
TextAlign
Text property of a RadioButton represents the current text
of a RadioButton control. The TextAlign property represents text alignment that
can be Left, Center, or Right. The following code snippet sets the Text and
TextAlign properties and gets the size of a RadioButton control.
dynamicRadioButton.Text = "I
am a Dynamic RadioButton"
dynamicRadioButton.TextAlign = ContentAlignment.MiddleCenter
Font
Font property represents the font of text of a RadioButton
control. If you click on the Font property in Properties window, you will see
Font name, size and other font options. The following code snippet sets Font
property at run-time.
dynamicRadioButton.Font = nNw
Font("Georgia",
16)
Read RadioButton
Contents
The simplest way of reading a RadioButton control contents is
using the Text property. The following code snippet reads contents of a RadioButton
in a string.
Dim RadioButtonContents As String = dynamicRadioButton.Text
Appearance
Appearance property of RadioButton can be used to set the
appearance of a RadioButton to a Button or a RadioButton. The Button look does
not have a round select option. The following property makes a RadioButton look
like a Button control.
dynamicRadioButton.Appearance = Appearance.Button
Check Mark
Alignment
CheckAlign
property is used to align the check mark in a RadioButton. By using CheckAlign
and TextAlign properties, we can place text and check mark to any position on a
RadioButton we want. The following code snippet aligns radio button round
circle and text to middle-right and creates a RadioButton that looks like
Figure 4.
dynamicRadioButton.CheckAlign = ContentAlignment.MiddleRight
dynamicRadioButton.TextAlign = ContentAlignment.MiddleRight
Figure 4
AutoEllipsis
An ellipsis character (...) is used to give an impression that a
control has more characters but it could not fit in the current width of the
control. If AutoEllipsis property is true, it adds ellipsis character to a
control if text in control does not fit. You may have to set AutoSize to false
to see the ellipses character. The following code snippet sets the AutoEllipsis
property of a RadioButton to true.
dynamicRadioButton.AutoEllipsis = True
Figure 5 shows a
RadioButton when AutoEllipsis is true and contents does not fit in the given
width of the control.
Figure
5
Image in RadioButton
The Image property of a
RadioButton control is used to set the background as an
image. The Image property needs an Image object. The Image class has a static
method called FromFile that takes an image file name with full path and creates
an Image object.
You can also align image and
text. The ImageAlign and TextAlign properties of RadioButton are
used for this purpose.
The following code snippet sets an
image as a RadioButton background.
dynamicRadioButton.Image = Image.FromFile("C:\Images\Dock.jpg")
dynamicRadioButton.ImageAlign = ContentAlignment.MiddleRight
dynamicRadioButton.FlatStyle = FlatStyle.Flat
RadioButton
States
A typical RadioButton
control has two possible states – Checked and Unchecked. Checked state is when
the RadioButton has check mark on and Unchecked is when the RadioButton is not
checked. Typically, we use a mouse to check or uncheck a RadioButton.
Checked
property is true when a RadioButton is in checked state.
dynamicRadioButton.Checked = True
Usually, we
check if a RadioButton is checked or not and decide to take an action on that
state something like following code snippet.
If (dynamicRadioButton.Checked) Then
Else
End If
AutoCheck
property represents whether the Checked or CheckState
values and the RadioButton's appearance are automatically changed when the RadioButton
is clicked. By default this property is true but if set to false.
dynamicRadioButton.AutoCheck = False
RadioButton Checked Event Hander
CheckedChanged event occurs
when the value of the Checked property changes. To add this event handler, you
go to Events window and double click on CheckedChanged events as you can see in
Figure 6.
Figure 6
The following code
snippet defines and implements these events and their respective event
handlers. You can write this code to implement CheckedChanged event
dynamically.
Friend WithEvents
RadioButton1 As System.Windows.Forms.RadioButton
Private Sub
RadioButton1_CheckedChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) _
Handles RadioButton1.CheckedChanged
End Sub
Summary
In this article, we discussed discuss how to create a RadioButton
control in Windows Forms at design-time as well as run-time. After that, we saw
how to use various properties and methods.