将 datagridViewComboboxColumn 中的键入文本项添加到数据库后的 vb.net 错误

Question

基本上，我不希望用户能够输入 datagridViewComboboxColumn 如果没有匹配，它会自动将文本保存到数据库中，更新 BindingSource 并选择项目。

这是我目前所拥有的。 绑定源：

With acctTitleCombo6
    .AutoComplete = True
    Try
        .DataSource = ds4
        .DisplayMember = "desc_description"
        .ValueMember = "desc_id"
        .DataPropertyName = "desc_id"
        .AutoSizeMode = DataGridViewAutoSizeColumnMode.Fill
    Catch ex As Exception
        MsgBox(ex.ToString)
    End Try
End With

在 EditingControlShowing 中将组合框样式更改为下拉：

Dim comboBoxColumn As DataGridViewComboBoxColumn = DataGridView2.Columns(0)
If (DataGridView2.CurrentCellAddress.X = comboBoxColumn.DisplayIndex) Then
    Dim cb As ComboBox = TryCast(e.Control, ComboBox)
    If (cb IsNot Nothing) Then
        cb.DropDownStyle = ComboBoxStyle.DropDown
    End If
End If

检查输入的文本是否已经在源项目中（CellValidating 事件）。

Dim comboBoxColumn As DataGridViewComboBoxColumn = DataGridView2.Columns(0)
cs2.Open()
Dim comm, comm2, comm3 As New MySqlCommand
comm.Connection = cs2
Dim msgAddDesc As String = "Your description is currently not in the list." & vbNewLine & _
    "Would you like to add '"

If (e.ColumnIndex = comboBoxColumn.DisplayIndex) And Not String.IsNullOrWhiteSpace(e.FormattedValue) Then
    Dim itemIE As IEnumerator = comboBoxColumn.Items.GetEnumerator
    itemIE.Reset()
    Dim thisItem As DataRowView
    Dim exist As Boolean = False
    While itemIE.MoveNext()
        thisItem = CType(itemIE.Current(), DataRowView)
        Dim valueMember As Object = thisItem.Row.ItemArray(0)
        Dim displayMember As Object = thisItem.Row.ItemArray(1)
        If displayMember.ToString = e.FormattedValue Then
            exist = True
        End If
    End While

    If exist = False Then
        If MessageBox.Show(msgAddDesc & e.FormattedValue & "' to the list?", "Does not exist", _
        MessageBoxButtons.YesNo) = Windows.Forms.DialogResult.Yes Then
           comm.CommandText = "INSERT INTO ref_description(desc_description) " & _
               "VALUES(@description)"
            With comm.Parameters
                .Add("@description", MySqlDbType.VarChar).Value = e.FormattedValue
            End With
            comm.ExecuteNonQuery()
            comm.Parameters.Clear()
        End If
    End If
End If
cs2.Close()

现在，每当我向数据库中添加新项目时，都会出现此错误，但有时不会：

The following exception occurred in the DataGridView:
System.FormatException: Value '' cannot be converted to type 'System.String'.

at System.Windows.Forms.DataGridViewComboBoxCell.ParseFormattedValue(Object formattedValue, DataGridViewCellStyle cellStyle, TypeConverter formattedValueTypeConverter, TypeConverter valueTypeConverter)
at System.Windows.Forms.DataGridView.PushFormattedValue(DataGridViewCell& dataGridViewCurrentCell, Object formattedValue, Exception& exception)

另一个问题是，我如何在将新项目添加到数据库后更新组合框，然后我还想在用户按 enter 或 tab 时自动选择新项目（仅当有新项目添加到数据库）。

Answer 1

我不确定，如果我能提供帮助。但是，错误来自 DataGridView，而不是组合。我怀疑，您同时更新了 datagridview（当您尝试更新组合时），这是行不通的。我认为您需要先完成单元格编辑（包括验证），然后才能更新 datagridview。我会尝试将其移至 CellEndEdit() 事件。

Answer 2

我如何更新组合框：我没有看到代码，你首先如何加载组合框。

通常，您只需更新相关数据集并将其重新分配给 ComboBox.DataSource，或者您可以使用数据绑定（无需更新，但如果需要更多绑定功能，通常会使用它）。

Private Sub LoadUpdateSubListCombo()
        Dim cmdText as String
        cmdText = "SELECT ID,SubName FROM SubmarinesTable "
        Dim ds as DataSet
        ds = MyDataAccessLayer.GetQueryResults(cmdText)
        Dim SubDT As DataTable = ds.Tables(0).DefaultView
        cb3.DataSource = SubDT
        cb3.ValueMember = "ID"
        cb3.DisplayMember = "SubName"
End Sub

...其中 cb3 是一个 ComboBox...