Unusual problem when setting Combobox Display/Value members

Infog · #1 December 30th, 2008, 07:59 PM

Using this code, the display member of the combo box is displaying the text "System.Data.DataViewManagerListItemTypeDescriptor ". Huh???

The first block of code gets the data from the database, and works as far as I know. The second block of code sets the first value of the form, and does NOT work like I want it too. I commented out the line that sets the value member, because it gives an exception.

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 Public Function FillFromAccess(ByVal QueryString As String, ByVal FillTable As String)
 
        Dim OLEConnString As String

        OLEConnString = "Provider=" & My.Settings.Connection_AccessProvider & ";" _

            & "Data Source=" & My.Settings.Connection_Location & ";" ' _

        '   & "Initial Catalog=Blah;" _

        '   & "User Id=username;" _

        '   & "Password='password';"
 
        Dim DBConn As New OleDbConnection(OLEConnString)
 
        Dim DBCommand As OleDbDataAdapter

        Dim DataSetAccess As New DataSet
 
        ' For any data needed, pull it out of the database.

        DBCommand = New OleDb.OleDbDataAdapter(QueryString, DBConn)

        ' Once that's ready, use it to fill the dataset DSPageData:

        DBCommand.Fill(DataSetAccess, FillTable)
 
        FillFromAccess = DataSetAccess
 
    End Function

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 Private Sub Add_action_items_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        'Load the job number into the job number combo box

        Dim SQL As String

        Dim DataSet_Jobs_Incomplete As New DataSet
 
        'Find the information from the database

        SQL = "Select * From Jobs WHERE Completed <> True"

        DataSet_Jobs_Incomplete = FillFromAccess(SQL, "Jobs_Incomplete")
 
        'Add the list of job numbers to the combo box

        With CmbJobNum

            .DataSource = DataSet_Jobs_Incomplete

            '.ValueMember = "ID"

            .DisplayMember = "Job_num"

            .SelectedIndex = 0

        End With
 
    End Sub

Infog · #2 December 30th, 2008, 09:39 PM

I found the problem! I feel kind of silly now.

I didn't know how to reference which table in the dataset to use, and I had swapped the valuemember and displaymember.

The code below works to set a combobox to a list, pulled from a database.

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 Private Sub Add_action_items_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        'Load the job number into the job number combo box

        Dim SQL As String

        Dim DataSet_Jobs_Incomplete As New DataSet
 
        'Find the information from the database

        SQL = "Select * From Jobs WHERE Completed <> True"

        DataSet_Jobs_Incomplete = FillFromAccess(SQL, "Jobs_Incomplete")
 
        'Add the list of job numbers to the combo box

        With CmbJobNum

            .DataSource = DataSet_Jobs_Incomplete.Tables(0)

            .ValueMember = "ID"

            .DisplayMember = "Job_num"

            .SelectedIndex = 0

        End With
 
    End Sub

Infog · #3 December 31st, 2008, 07:17 PM

More advice, for whoever may be researching this topic later -

If the correctly formed query you send to the database returns no records, VB.NET will give an exception. To stop that, catch the exception and send back the value Nothing. Now, it skips the exception, and you can test for Nothing in the sub that used the above function. That way, no controls are set to an index (ComboBox1.Index = 0) when their index doesn't actually exist.

I hope my past mistakes can be put to use by someone else...

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        Try

            DBCommand.Fill(DataSetAccess, FillTable)

        Catch ex As Exception

            FillFromAccess = Nothing

            Exit Function

        End Try

Unusual problem when setting Combobox Display/Value members

re: Unusual problem when setting Combobox Display/Value members

re: Unusual problem when setting Combobox Display/Value members

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