Dropdownlist add handler

[daniel50096230]

Hi,

I would like to add handler to a dropdownlist which is dynamically created. I have the following code:

Dim ddl1 as new Dropdownlist

ddl1.DataTextField = "Hours"
ddl1.DataValueField = "HourID"
ddl1.DataSource = GetHours()
ddl1.DataBind()

How can I add handler to the ddl1 so that when ddl1 selected index changed, then the text in the ddl1 will be assigned to Textbox1.text?


Can anyone advice?

[David Anton]

Use the 'AddHandler' operator to wire up event handling at run time.

e.g.,

AddHandler someObject.someEvent, AddressOf someMethod

[DataMiser]

SelectedIndexChanged is an included event, no need to write and new one.

Double click on the combo box and it should place you in the code block for the event you mention. Just put your code to update the textbox in that event.

[David Anton]

The OP's control is dynamically created - that's exactly what 'AddHandler' is for.

[DataMiser]

I guess I missed that part.. carry on

[HanneSThEGreaT]

The OP's control is dynamically created - that's exactly what 'AddHandler' is for.

Hi David.

Actually, I don't agree with using the AddHandler here. Why? Well, why hasn't this dropdownlist control not set up to Inherit from ComboBox? If it is indeed inheriting from CombBox, why re invent the wheel with new handlers and so on. This is exactly why Inheritance exists, so that the child class can make use of the base class' methods and properties.

[DataMiser]

I have not tried this but I thought I would throw it out there.

Have you tried to define the dropdownlist with events? I am thinking that this should give you access to all the events you would have with a drop down list or am I missing something here?

[JohnnyD]

What exactly is a dropdown list? Assuming it is some kind of customised ComboBox you should do this:

Public Class Form1
    Inherits System.Windows.Forms.Form

    Private WithEvents _dropDownList1 As ComboBox

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        _dropDownList1 = New ComboBox
        _dropDownList1.Size = New Size(200, 40)
        _dropDownList1.Location = New Point(20, 100)
        _dropDownList1.Parent = Me
        _dropDownList1.Show()

        _dropDownList1.Items.Add("Item1")
        _dropDownList1.Items.Add("Item2")

        AddHandler _dropDownList1.SelectedIndexChanged, AddressOf _dropDownList1_SelectedIndexChanged

    End Sub

    Private Sub _dropDownList1_SelectedIndexChanged(ByVal sender As Object, ByVal e As EventArgs)
        ' Do something when the selected index changes


    End Sub
End Class

[HanneSThEGreaT]

When you declare an object using WithEvents you do not need AddHandler at all, as the events will alread be "loaded" as well. We have established that. The only two options would be to either Inherit from the ComboBox class or using WithEvents.

[JohnnyD]

Sorry, you're right. I stand corrected.

[HanneSThEGreaT]

That's how we learn