我的vb.net应用程序中有一个表单，用于获取有关退回库存的数据。表格包含两个组合框。一个名为combobox5，包含发票号，另一个名为combobox3，包含聚会代码。两个组合框都使用sqldataadapter预加载。
现在我想要的是在combobox5中更改发票号时更改combobox3中的聚会代码。进一步说明，当发行股票时，聚会代码与发票号一起存储，以跟踪发行股票的当事方。现在当退回库存时，我想跟踪哪一方已退回库存，并且我希望在发票号更改时自动选择聚会代码，并且应该根据该特定发票号存储在数据库中。 ...
我正在使用以下代码：
Private Sub ComboBox5_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles ComboBox5.SelectedIndexChanged
' defines a new connection to the database
Dim con As New SqlConnection("Data Source=TAHA;Initial Catalog=ADT;Integrated Security=True")
con.Open()
If ComboBox5.SelectedIndex = 0 Then
ComboBox3.Enabled = True
If Not ComboBox3.Items.Count = 0 Then
ComboBox3.SelectedIndex = 0
End If
Else
Me.ComboBox3.Enabled = False
Me.ComboBox3.BackColor = Color.White
Me.ComboBox3.ForeColor = Color.Black
Dim invoices As New SqlCommand("select invoice_no, party_code from Outgoing_Invoice group by invoice_no, party_code", con)
Dim reader As SqlDataReader = invoices.ExecuteReader
While reader.Read
Dim cnt, i As Integer
cnt = Me.ComboBox3.Items.Count
If Me.ComboBox5.SelectedItem.ToString.Trim = reader("invoice_no").ToString.Trim Then
If Not cnt = 0 Then
For i = 0 To cnt - 1
If Me.ComboBox3.Items.Item(i).ToString.Trim.Contains(reader("party_code").ToString.Trim) Then 'here i have also used equals instead of contains but that too doesn't work
Me.ComboBox3.SelectedIndex = i
Exit For
End If
Next
End If
End If
End While
reader.Close()
End If
con.Close()
End Sub