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Resources » Articles » .NET Framework »
Ways to trigger windows form Control's event
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In this article, we can see the various ways of triggering the Control's Event.
Some times we may want to perform the same functionality as a button control does, from another control, say another button or Checkbox etc.
In such scenarios, it will be useful to trigger the event handler from other controls.
There are Three ways to trigger Conrols Event
1. Perform the event by the Assigned Control itself.
2. Call the Event Handler by passing Null as parameters For both Sender and Args Parameter.
3. Calling the Event Handler by passing Control Name as parameters For Sender and Null For Args Parameter.
To illustrate this, let us consider the following Form and Controls.
a) A Form, and name it as Myform.
b) a button and name it as Button1
c) a button and name it as Button2
d) a ComboBox and name it as ComboBox1
and we will see how the Button1's Click Event Handler is going to be handled by all other controls and Button1.
Public Sub New()
'Assigning text property of the controls
me.Button1.Text = "I am Button 1"
me.Button2.Text = "I am Button 2"
me.ComboBox1.Items.Add ("1")
me.ComboBox1.Items.Add ("2")
me.ComboBox1.Items.Add ("3")
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As_
System.EventArgs) Handles Button1.Click
Dim myComboBox As ComboBox
Dim myButton As Button
'code to perform action when Button is clicked
If Sender Is Nothing Then
MessageBox.Show (Button1.Text)
End If
If TypeOf sender Is Button Then
myButton = CType(sender, Button)
'Just to display the text of the control as an illustration
MessageBox.Show (myButton.Text)
ElseIf TypeOf sender Is ComboBox Then
myComboBox = CType(Ctrl, ComboBox)
MessageBox.Show (myComboBox.SelectedItem.ToString)
End If
End Sub
Perform the event by the Assigned Control itself.(Button1)
In this case,
a. we can just click on the Button1. The Event handler will be invoked.
The Text "I am Button1" will be displayed
b. Call Button1's PerformClick() Method
Button1.PerformClick()
It will also invoke Button1's Event handler
passing Null as parameters For both Sender and Args Parameter.
1. Triggering the Button1's Click Event using Button2's Click
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As_
System.EventArgs) Handles Button1.Click
'Calling Button1's Click Event by passing Sender as Button2 And
'Args As Nothing
Button1_Click (sender, Nothing)
End Sub
2. Triggering the Button1's Click Event using ComboBox1's selectedIndexChanged
Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
Button1_Click (sender, Nothing)
End Sub
Calling the Event Handler by passing Control Name as parameters For Sender and Null For Args Parameter.
1. Triggering the Button1's Click Event using Button2's Click
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As_
System.EventArgs) Handles Button1.Click
'Calling Button1's Click Event by passing Sender And
'Args As Nothing
Button1_Click (Nothing, Nothing)
End Sub
2. Triggering the Button1's Click Event using ComboBox1's selectedIndexChanged
Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
'Calling Button1's Click Event by passing Sender And
'Args As Nothing
Button1_Click (Nothing, Nothing)
End Sub
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