CODEWITHSUNDEEP
.netvb.netcombobox
Rusnnja
Rusnnja

Reputation: 13

How to make a MessageBox pop up only if the value in ComboBox changes

I'm trying to make the MessageBox pop up whenever the value in the combobox changes, instead, it currently pops up on the load and then when the value changes. Not sure what I'm doing wrong here.

Public Class DropDownBox

Private Sub DropDownBox_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    Dim dropSource As New Dictionary(Of String, String)()
    dropSource.Add("", "")
    dropSource.Add("1", "1")
    dropSource.Add("2", "2")
    dropSource.Add("3", "3")
    dropSource.Add("4", "4")
    dropSource.Add("5", "5")
    dropSource.Add("6", "6")
    dropSource.Add("7", "7")
    dropSource.Add("8", "8")
    dropSource.Add("9", "9")
    dropSource.Add("10", "10")

    cbox.DataSource = New BindingSource(dropSource, Nothing)
    cbox.DisplayMember = "Value"
    cbox.ValueMember = "Key"

    cbox.Text = Nothing

End Sub


Private Sub cbox_TextChanged(sender As Object, e As EventArgs) Handles cbox.TextChanged

    If cbox.Text IsNot Nothing Then
        MsgBox("Are you sure?")
    Else

    End If

End Sub

End Class

Thank you for your help.

Please let me know if you need any additional information on this subject, I've searched all over and haven't been able to figure this out.

Upvotes: 0

Views: 85

Answers (3)

Fabio
Fabio

Reputation: 32455

Event Combobox.SelectionChangeCommitted perfectly fit your requirement without extra workarounds.

The SelectionChangeCommitted event is raised only when the user changes the combo box selection

ComboBox.SelectionChangeCommitted Event

Private Sub cbox_SelectionChangeCommitted(sender As Object, e As EventArgs) 
                                                      Handles cbox.SelectionChangeCommitted

    Dim combobox = DirectCast(sender, ComboBox)
    If combobox.Text IsNot Nothing Then
        MsgBox("Are you sure?")
    End If

End Sub

Upvotes: 3

Patrick
Patrick

Reputation: 196

I like Youssef's answer, and use that when I have multiple objects, such as an array of controls, that share the same event handler. The downside is that you don't get to identify the event handler in the object's events in the comboboxes at the top of the editor, nor see the routine identified as the handler in the code.

I like this approach:

Private Sub cbox_TextChanged(sender As Object, e As EventArgs) Handles cbox.TextChanged
    If Not Me.IsHandleCreated Then Return

    If cbox.Text IsNot Nothing Then
        MsgBox("Are you sure?")
    Else

    End If

End Sub

You can also use cbox.IsHandleCreated

Upvotes: 2

Youssef13
Youssef13

Reputation: 4954

I think the value is changing already on loading form.

Anyway here is my idea

Firstly, Remove the event handler, so this line

Private Sub cbox_TextChanged(sender As Object, e As EventArgs) Handles cbox.TextChanged

should be

Private Sub cbox_TextChanged(sender As Object, e As EventArgs)

Secondly, Add the handler again at the end of the form_load by this line

AddHandler cbox.TextChanged, AddressOf cbox_TextChanged

Upvotes: 1

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