VB.NET - How to add a large amount of events to a single handle? - vb.net

Question

Recently I've been working on a program that has a few TextBoxes, CheckBoxes, ComboBoxes, etc., and I found that making one function handle multiple events is pretty simple, you just separate the events with a comma and the code recognizes the inidvidual events.
Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click, Button2.Click
MsgBox("Hello World!")
End Sub
However, when you start to have a large number of events that you want handled by the same function, it gets a bit messy.
Private Sub Checks_CheckedChanged(sender As Object, e As EventArgs) Handles chkInput1.CheckedChanged, chkInput2.CheckedChanged, chkInput3.CheckedChanged, chkInput4.CheckedChanged, checkInput5.CheckedChanged, chkOutput.CheckedChanged
MsgBox("Checks Changed!")
End Sub
You can use the line continuation character _ to make it look a little better.
Private Sub Checks_CheckedChanged(sender As Object, e As EventArgs) Handles _
chkInput1.CheckedChanged, chkInput2.CheckedChanged, chkInput3.CheckedChanged, _
chkInput4.CheckedChanged, checkInput5.CheckedChanged, chkOutput.CheckedChanged
MsgBox("Checks Changed!")
End Sub
But you still end up with a nasty block of text. Is there a more clean/concise way of doing this? What I have in mind is that it would be really nice to give an array of object events as an argument but I don't think that's possible.

Answer 1

You could do this by using the
AddHandler ObjectName.EventName, AddressOf EventHandlerName
syntax
It's simple enough to write a Sub that takes an array of object and loops over them to add the handler for each event.
For checkboxes:
Public Sub AddHandlerSub(PassedArray As CheckBox())
For Each item As CheckBox in PassedArray
AddHandler Item.CheckedChanged, AddressOf EventHandlerName
next
End Sub

Answer 2

You can simply iterate the controls in the controls collection and not fuss with an array at all. You can also do further conditions if you want to exclude/add any given control, such as in the example of the TextBox Case in the following example.
Private Sub DataTables_Load(sender As Object, e As EventArgs) Handles MyBase.Load
For Each Ctrl As Control In Panel1.Controls
Select Case Ctrl.GetType
Case GetType(CheckBox)
AddHandler DirectCast(Ctrl, CheckBox).CheckedChanged, Sub(S As Object, EA As EventArgs)
Dim ChkBox As CheckBox = DirectCast(S, CheckBox)
'do something with ChkBox
End Sub
Case GetType(TextBox)
Select Case Ctrl.Name
Case "TextBox1", "TextBox2" 'Add handle only to these contrls
'Or you could add Case Else and put the below handle within it
'Then this becomes an exclusion case
AddHandler DirectCast(Ctrl, TextBox).TextChanged, Sub(S As Object, EA As EventArgs)
Dim TxtBox As TextBox = DirectCast(S, TextBox)
'do something with TxtBox
End Sub
End Select
End Select
Next
End Sub

Answer 3

Additional Information: You can select procedures as Event Handlers by selecting the control. Then in the Properties window click the lightning bolt to display Events. Selected the event you wish to assign a handler and then the drop down arrow to the right. The resulting list will display all the Subs that match the signature of that event. Select the one you want and the designer will write or append the control to the Handles clause.
Add a procedure to the Form with a signature that matches the event.
Private Sub MultipleButtons(sender As Object, e As EventArgs)
End Sub
In the dropdown the list contains all Subs that match the signature of the event.
The designer writes the Handles clause
Private Sub MultipleButtons(sender As Object, e As EventArgs) Handles Button5.Click
End Sub