如何从Visual Basic 2013中的组合框的选定项中获取关联列的值？

Question

I am working with Visual Basic 2013 and sqlite. My table structure is like -

• topic_id
• topic_name
• subject_id
• subject_name
• chapter_no

I am importing this table into combo box as -

 Dim con As SQLiteConnection
 Dim sql As String
 Dim da As SQLiteDataAdapter
 Dim ds As New DataSet
 Dim cmd As New SQLiteCommand

 con = New SQLiteConnection("Data Source = test.db;Version=3;")
 con.Open()
 sql = "SELECT * FROM med_topics"
 da = New SQLiteDataAdapter(sql, con)
 da.Fill(ds, "TopicsList")
 con.close()
 cboTopicsList.DisplayMember = "Topic_Name"
 cboTopicsList.ValueMember = "Topic_Id"
 cboTopicsList.DataSource = ds.Tables("TopicsList")

I want to use tables other column's value (but don't want them to display in combo box) viz. "subject_id, subject_name, chapter_no". I know these values are imported in TopicsList , but I don't know, how to get the corresponding value of the selected item. I am stuck here.

Answer 1

A ComboBox populate its object collection (the Items property) with DataRowView objects when bound to a DataTable . This is because the DataTable class implements IListSource which the ComboBox looks for. It returns a DataView , the DefaultView of the table.

Private Sub cboTopicsList_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cboTopicsList.SelectedIndexChanged
    Dim rowView As DataRowView = TryCast(cboTopicsList.SelectedItem, DataRowView)
    If (Not rowView Is Nothing) Then
        Dim row As DataRow = rowView.Row
        Dim subjectName As String = DirectCast(row.Item("subject_name"), String)
        '...
    End If
End Sub