VB Windows APP: ComboBox SelectedValue

[Frinavale]

This question is going to sound a little crazy but.........How do you set the selected item in a ComboBox?

I am populating a ComboBox with a bunch of instances of a custom private class:

For Each s as Something In MyListOfSomethings
 MyComboBox.Items.Add(New XYZListItem(s.ID,s.description))
Next
MyComboBox.ValueMember = "ID"
MyComboBox.DisplayMember = "Description"
 

Here's the Private Class

Private Class XYZListItem
  Private _description As String
        Private _id As Integer
        Public Property Description() As String
            Get
                Return _description
            End Get
            Set(ByVal value As String)
                _description = value
            End Set
        End Property
        Public Property ID() As Integer
            Get
                Return _id
            End Get
            Set(ByVal value As Integer)
                _id = value
            End Set
        End Property
        Public Sub New(ByVal theID As Integer, ByVal theDescription As String)
            _id = theID
            _description = theDescription
        End Sub
End Class

Now the descriptions of the objects are displayed in the ComboBox and when the user selects an Item I'm able to grab the ID from the SelectedItem and do stuff with it.

My problem is that I want to set the selected item through the SelectedValue property and I can't seem to do so:

      MyComboBox.SelectedValue = value 'Value being a valid ID for an item listed in the ComboBox
 

According to this article:

The SelectedValue property can also be used to select an item in the list control by setting it with the value of the item. If no items in the list control contain the specified value, a System..::.Argu mentOutOfRangeE xception is thrown.

...using the SelectedValue to set the selected item should be possible...so, since what I'm doing doesn't work (I'm getting no exception....th e SelectedValue just remains a value Nothing) how do you set the selected item without having to:

Loop through the items in the ComboBox
Find a reference to the one with the ID matching
And then set the ComboBox SelectedItem to the one I found..

(For example...)

Dim item As XYZListItem
For Each thing As XYZListItem In MyComboBox.Items
  If value = thing.ID Then
    item = thing
    Exit For
  End If
Next
MyComboBox.SelectedItem = item
 

-Frinny

[DrBunchman]

Hi Frinny,

Did you mean to post this in .NET? :-)

Dr B

[Frinavale]

Hi Frinny,

Did you mean to post this in .NET? :-)

Dr B

>>blush<<

I gotta stop doing that!

(especially since this question has nothing to do with web development!)

-Frinny

[Plater]

What you are doing seems like it should work with the SelectedValue, not sure why it doesn't.
Are you able to maybe switch to a Dictionary<IDTy pe,Something> collection and set it as your data source (or something like that instead. Then you can reference the Dictionary with the ID and get the item to set to SelectedItem?

When the combobox is just strings, I use the .Items.Contains ("string value I want")

When the combobox uses a datasource (mine are always DataTables, sorry), I had to jump through some hoops.

//dd is the DataTable that was used as a datasource
DataRow[] dd = dt.Select("[Client Company] ='Philips Healthcare'");
int rowidx = dt.Rows.IndexOf(dd[0]);
cbClientCompany.SelectedItem = dt.DefaultView[rowidx];
 

Only thing I could think of is maybe you can use the SelectedIndex proeprty instead?

[Frinavale]

What you are doing seems like it should work with the SelectedValue, not sure why it doesn't.
Are you able to maybe switch to a Dictionary<IDTy pe,Something> collection and set it as your data source (or something like that instead. Then you can reference the Dictionary with the ID and get the item to set to SelectedItem?

I'll look into this...but I'd really prefer not to use a Dictionary.
I'm working on an example application for other developers to reference so that they understand how to use certain functionality. Since I have no idea how much my audience knows about software development I was even reluctant to introduce the very simple private class described above....

I just didn't feel like adding the ID to the string displayed in the combo box...only to have to parse the string later (I find parsing Strings a chore and it can complicate examples)

When the combobox is just strings, I use the .Items.Contains ("string value I want")

When the combobox uses a datasource (mine are always DataTables, sorry), I had to jump through some hoops.

//dd is the DataTable that was used as a datasource
DataRow[] dd = dt.Select("[Client Company] ='Philips Healthcare'");
int rowidx = dt.Rows.IndexOf(dd[0]);
cbClientCompany.SelectedItem = dt.DefaultView[rowidx];
 

Interesting.... .

Only thing I could think of is maybe you can use the SelectedIndex proeprty instead?

This wont simplify things because I don't know what index the item's ID exists at....I'd still have to loop through the items in the combo box to find the index.

-Frinny

[Plater]

Well how do you know which "id" you want to set?
SelectedItem returns the isntance of your class (and all the properties associated with it) for that item.
Somewhere you have to get the ID value you want to set that combobox to, could you not get some other value (like possibly the entire instance of your private class) and use it to select?

[Frinavale]

Well how do you know which "id" you want to set?
SelectedItem returns the isntance of your class (and all the properties associated with it) for that item.
Somewhere you have to get the ID value you want to set that combobox to, could you not get some other value (like possibly the entire instance of your private class) and use it to select?

The above code exists in a user control (let's call it the HelperControl).

The HelperControl is used within many other controls that require the functionality the HelperControl offers.


In order to configure the HelperControl to display "default" data ...the parent control calls a function offered by the HelperControl and passes the ID of the item that should be selected.

The parent control has no idea about the item descriptions listed in the ComboBox in the HelperControl.. .just the ID of the item.

[Plater]

I believe the selected value problem comes from using Items.Add() and not a DataSource.
Testing has confirmed this.
I used an array of XYZListItem ( XYZListItem[] xxx = new XYZListItem[6])
And the SelectedValue was getting/setting correctly and changing the combobox just fine

[Frinavale]

I believe the selected value problem comes from using Items.Add() and not a DataSource.
Testing has confirmed this.
I used an array of XYZListItem ( XYZListItem[] xxx = new XYZListItem[6])
And the SelectedValue was getting/setting correctly and changing the combobox just fine

You've got to be kidding me!
I'm going to try it now.

[Frinavale]

It's working.
Plater I'd hug you if you were here :)

Thanks a lot for looking into this for me because I spent a few hours trying to figure out why it wasn't working.

I'm still not sure why the SelectedValue property works when you set the data source property....and why it doesn't work if you add individual items to the ComboBox...I'll have to look into it further later.

I'm just glad that I don't have to loop through all the items.

Thanks again!

-Frinny