[RESOLVED] [2008] How to get Itemdata of combobox item

[Nitesh]

Hi Guys,

I currently have this code to load a combobox. I also have a class to set the itemdata and text for each item.

my problem is that when the form loads I have another query that selects a classid for a student. I want to compare the itemdata for each item in the combobox against the current classid for that pupil and then set the selectedindex of the combo where that classid is. How can I do it. Please help.

Private Sub LoadClassCombo()
        Dim myDataReader As MySqlDataReader

        Using con As New MySqlConnection

            Dim strsql As String = "SELECT classid,CONCAT_WS(' ',gradelevel,class) from classes ORDER BY Gradelevel;"

            Dim cmd As New MySqlCommand

            With cmd
                .Connection = New MySqlConnection(myConnStr)
                .Connection.Open()
                .CommandText = strsql
                myDataReader = .ExecuteReader

            End With

            With cboClass
                .Items.Clear()

                Do While myDataReader.Read
                    .Items.Add(New ComboListData(myDataReader.GetString(1), myDataReader.GetString(0)))
                Loop

            End With

        End Using

    End Sub

class:

Public Class ComboListData

    Private sName As String
    Private iID As Long

    Public Sub New()
        sName = ""
        iID = 0
    End Sub

    Public Sub New(ByVal Name As String, ByVal ID As Long)
        sName = Name
        iID = ID
    End Sub

    Public Property Name() As String
        Get
            Return sName
        End Get

        Set(ByVal sValue As String)
            sName = sValue
        End Set
    End Property

    Public Property ItemData() As Long
        Get
            Return iID
        End Get

        Set(ByVal iValue As Long)
            iID = iValue
        End Set
    End Property

    Public Overrides Function ToString() As String
        Return sName
    End Function

End Class

[Deepak Sakpal]

TextBox1.Text = CType(cboClass.SelectedItem, ComboListData).ItemData

[jmcilhinney]

Instead of adding your ComboListItems to the ComboBox directly, add them to a List or BindingList, then bind that to the ComboBox.

Dim items As New List(Of ComboBoxItem)
 
While myDataReader.Read()
    items.Add(New ComboListData(myDataReader.GetString(1), myDataReader.GetString(0)))
End While
 
Me.cboClass.DisplayMember = "Name"
Me.cboClass.ValueMember = "ItemData"
Me.cboClass.DataSource = items

You then get the ItemData value that corresponds to the selected Name value like so:

Dim itemData As String = CStr(Me.cboClass.SelectedValue)

[Nitesh]

Hi Deepak,

Thanks for the reply . I tried this but I get an error:

Argument 'Prompt' cannot be converted to type 'String'.

For j = 0 To cboClass.Items.Count

                If CurClassId = CType(cboClass.Items(j), ComboListData).ItemData Then

                End If


            Next

[jmcilhinney]

Hi Deepak,

Thanks for the reply . I tried this but I get an error:

Argument 'Prompt' cannot be converted to type 'String'.

For j = 0 To cboClass.Items.Count

                If CurClassId = CType(cboClass.Items(j), ComboListData).ItemData Then

                End If


            Next

You didn't get it on any of that code because there's no method there with an parameter named "Prompt".

[jmcilhinney]

Hey, I just realised, you've declared your ItemData property as type Long and your ComboBoxItem constructor has a corresponding Long parameter, yet when you create the ComboBoxItem objects you're specifically getting a String and passing it to that parameter.

.Items.Add(New ComboListData(myDataReader.GetString(1), myDataReader.GetString(0)))

What's up with that?

[Nitesh]

Hi jmcilhinney,

When I try this line of code:

Dim items As New List(Of ComboBoxItem)

the ComboBoxItem has that blue squiggly line under it. It isn't recognised. Am i doing something wrong.

[Deepak Sakpal]

Your class name is ComboListData and not ComboBoxItem and the error you are talking about is not with the code i posted. I am sure there something wrong at different place.

[Nitesh]

Hey, I just realised, you've declared your ItemData property as type Long and your ComboBoxItem constructor has a corresponding Long parameter, yet when you create the ComboBoxItem objects you're specifically getting a String and passing it to that parameter.

oops

plz correct it for me.

[Nitesh]

sorry guys, but I need to loop through all the itemdata. How can I do that

[jmcilhinney]

Whether you're doing as you were originally or you've changed to what I suggested, you have a collection of ComboListData items. Just use a For Each loop to visit each one and get its ItemData property.

[Nitesh]

please, please give me an example of how i would do the for each using the list.

I tried this but I can't get it to work:

For j = 0 To items.Count

                If CLng(items(j).ItemData) = CurClassId Then

                    cboClass.SelectedIndex = j

                End If

            Next

This is probably the last step. BTW I have switched to your suggestion jmcilhinney

[Deepak Sakpal]

For j = 0 To items.Count
    If CType(items(j), ComboListData).ItemData = CurClassId Then
        cboClass.SelectedIndex = j
    End If
Next

[jmcilhinney]

For Each item As ComboListData In items
    MessageBox.Show(item.ItemData.ToString())
Next

The 'items' in the above code could be the generic List I suggested earlier, or it could be the ComboBox's Items collection.

[Nitesh]

thanks alot guys, it is working great . I appreciate the help

[jim25m]

How to extract itemdata of the selected Item, without looping. Thanks.