vb.net - DropDownStyle（DropDownList）的ComboBox控件无法显示数据

Question

我有以下要求，

我有一个 ComboBox 控件（DropDownList 样式），用户必须选择一个给定的值，但不能编辑。然后我将它保存到数据库表中，它工作正常。

(dataRow("it_discount_profile") = Trim(cmbDisProfile.Text))

但是，当我尝试通过从数据库中检索它来在同一个 ComboBox 中显示相同的数据时，它不会显示。

(cmbDisProfile.Text = Trim(tempTb.Rows(0).Item("it_discount_profile")))

当我将 ComboBox 更改为“DropDown Style”时，它可以工作。但随后用户可以对其进行编辑。

我在这里遗漏了什么还是那样？任何建议将不胜感激。

我使用一个过程在运行时填充它。

Private Sub filldisProfiles()
    Dim sqlString As String = "SELECT discount_profile FROM tb_discount_profiles"
    Dim tempTb As DataTable
    Dim myTbClass As myClassTableActivities = New myClassTableActivities()
    tempTb = myTbClass.myFunctionFetchTbData(sqlString)

    cmbDisProfile.DataSource = tempTb
    cmbDisProfile.DisplayMember = "discount_profile"
End Sub

好的。实际上，我试图将我的一个旧项目从 VB 迁移到 VB.Net。VB.Net 对我来说并不新鲜。我使用自建类来减少其他地方的代码。我附上下面的课程。

我的实际要求是从表格中填充组合框。我喜欢在运行时做。我不希望用户编辑它。如果他们想添加一个新值，他们有单独的地方（表格）。我认为我做错了。如果可能，请提供示例代码，因为我不熟悉建议的方法。

Public Function myFunctionFetchTbData(ByVal inputSqlString As String) As DataTable
    Try
        Dim SqlCmd As New SqlCommand(inputSqlString, conn)
        Dim dataAdapter As New SqlDataAdapter(SqlCmd)

        Dim fetchedDataSet As New DataSet
        fetchedDataSet.Clear()
        dataAdapter.Fill(fetchedDataSet)

        Dim fetchedDataTable As DataTable = fetchedDataSet.Tables(0)

        Return fetchedDataTable

    Catch ex As Exception
        MsgBox(Err.Description)
    End Try
End Function

' this sub will update a table
Public Sub MyMethodUpdateTable(ByVal sqlString As String, ByVal tbToUpdate As DataTable)

    Dim SqlCmd As New SqlCommand(sqlString, conn)
    Dim dataAdapter As New SqlDataAdapter(SqlCmd)
    Dim objCommandBuilder As New SqlClient.SqlCommandBuilder(dataAdapter)
    dataAdapter.Update(tbToUpdate)

End Sub

Public Function MyMethodfindRecord(ByVal strSearckKey As String, ByVal tableName As String, ByVal strColumnName As String) As Boolean
    Try
        Dim searchSql As String = "SELECT * FROM " & tableName & " WHERE " & strColumnName & "='" & strSearckKey & "'"

        'Dim searchString As String = txtCategoryCode.Text
        '        searchOwnerCmd.Parameters.Clear()
        '        searchOwnerCmd.Parameters.AddWithValue("a", "%" & search & "%")

        Dim tempTb As DataTable
        Dim myTbClass As myClassTableActivities = New myClassTableActivities()
        tempTb = myTbClass.myFunctionFetchTbData(searchSql)

        If tempTb.Rows.Count = 0 Then
            Return False
        Else
            Return True
        End If

    Catch ex As Exception
        MsgBox(Err.Description)
    End Try
End Function
Public Function myFunctionFetchSearchTB(ByVal inputSqlString As String) As DataTable
    Try
        Dim SqlCmd As New SqlCommand(inputSqlString, conn)
        Dim dataAdapter As New SqlDataAdapter(SqlCmd)

        Dim fetchedDataSet As New DataSet
        fetchedDataSet.Clear()
        dataAdapter.Fill(fetchedDataSet)

        Dim fetchedSearchTB As DataTable = fetchedDataSet.Tables(0)

        Return fetchedSearchTB

    Catch ex As Exception
        MsgBox(Err.Description)
    End Try
End Function

标签： vb.netcomboboxdata-retrieval

Answer 1

谢谢大家的建议。唯一可以做到的方法就是你说的方法。我想把工作代码和一些要点放在所有人的利益上。

建议的，

• ComboBox1.SelectedIndex = comboBox1.FindStringExact(Trim(tempTb.Rows(0).Item("it_discount_profile")))"

当您将数据表绑定到组合框时不起作用。如果上述“SelectedIndex”方法有效，则应在运行时将这些值添加到组合框中。将项目添加到组合框的代码如下（myClassTableActivities 是我自己定义的一个类，如上所示），

Private Sub filldisProfiles()
    Dim sqlString As String = "SELECT discount_profile FROM tb_discount_profiles"
    Dim tempTb As DataTable
    Dim myTbClass As myClassTableActivities = New myClassTableActivities()
    tempTb = myTbClass.myFunctionFetchTbData(sqlString)

    Dim i As Integer = 0
    For i = 0 To tempTb.Rows.Count - 1
        cmbDisProfile.Items.Add(Trim(tempTb.Rows(i).Item("discount_profile")))
    Next
End Sub

添加后我们可以使用以下代码在组合框（DropDownList）上显示数据。

Private Sub txtItCode_TextChanged(sender As Object, e As EventArgs) Handles txtItCode.TextChanged
    Try
        Dim sqlString As String = "SELECT * FROM tb_items where it_code='" & Trim(txtItCode.Text) & "'"
        Dim tempTb As DataTable
        Dim myTbClass As myClassTableActivities = New myClassTableActivities()
        tempTb = myTbClass.myFunctionFetchTbData(sqlString)

        If Len(txtItCode.Text) < 4 Then
            cmdAdd.Enabled = False
            cmdDelete.Enabled = False
            cmdSave.Enabled = False
        Else
            If tempTb.Rows.Count > 0 Then


                With tempTb
                    txtItName.Text = Trim(tempTb.Rows(0).Item("it_name"))
                    cmbDisProfile.SelectedIndex = cmbDisProfile.FindStringExact(Trim(tempTb.Rows(0).Item("it_discount_profile")))
                    cmbProfitProfile.SelectedIndex = cmbProfitProfile.FindStringExact(Trim(tempTb.Rows(0).Item("it_profit_profile")))
                    cmbItCategory.SelectedIndex = cmbItCategory.FindStringExact(Trim(tempTb.Rows(0).Item("it_category")))
                    cmbFinanCategory.SelectedIndex = cmbFinanCategory.FindStringExact((tempTb.Rows(0).Item("it_finance_category")))
                End With
                cmdAdd.Enabled = False
                cmdDelete.Enabled = True
                cmdSave.Enabled = True
            Else
                cmdAdd.Enabled = True
                cmdDelete.Enabled = False
                cmdSave.Enabled = False
                txtItName.Text = ""
                Call fillItCategories()
                Call fillProProfile()
                Call filldisProfiles()
                Call fillFinCat()
            End If
        End If
    Catch ex As Exception
        MsgBox(ex.Message)
    End Try