DotNet · 2022年5月15日

当DataGridView在VirtualMode模式下NewRowNeeded和UserAddedRow事件以及RowsAdded的区别使用

NewRowNeeded事件当 VirtualMode 属性为 true 时,将在用户定位到 DataGridView 底部的新行时发生,适合给新行建立一些默认数据和按规则应该产生的数据,但此时不推荐添加新数据到后台数据表中。因为用户操作有太多的变数,可以把产生的默认值直接赋值给一个临时初始数据对像即可,在用户触发UserAddedRow事件后,再赋值到后台数据也不迟

    Private pInitData As OuterExtendItem
    Private Sub xDataGridView_NewRowNeeded(sender As Object, e As System.Windows.Forms.DataGridViewRowEventArgs) Handles xDataGridView.NewRowNeeded
        If (mHalt OrElse mGaugeConfig.mOPCItems Is Nothing) Then

            Return
        End If
        If (mGaugeConfig.mOPCItems.Count < 15) Then
            _InitData = New OPCItemConfig(mGaugeConfig.mGID)
            With _InitData
                .fMin = Convert.ToDouble(Int16.MinValue)
                .fMax = Convert.ToDouble(Int16.MaxValue)
                .mRemark = ""
                .mUnitAdjust = 1.0
                .mDataField = _fieldList(0).mValue
            End With
        Else
            If (xDataGridView.RowCount > mGaugeConfig.mOPCItems.Count + 1) Then
                xDataGridView.CancelEdit()
            End If
            MsgBox("OPC项最多只允许配置15个!", MsgBoxStyle.OkOnly, MyHub.mBase.appTitle)
        End If
 
        checkControl()
    End Sub

UserAddedRow事件是在编辑新行时触发,此时适合添加数据到后台数据表中
如例:
    Private Sub xDataGridView_UserAddedRow(sender As Object, e As System.Windows.Forms.DataGridViewRowEventArgs) Handles xDataGridView.UserAddedRow
        If (mHalt) Then
            Return
        End If
        If (_ExtendList Is Nothing) Then
            Return
        End If
        If (pInitData IsNot Nothing) Then
            _ExtendList.addNotEvent(pInitData)
            pInitData = Nothing
        End If
    End Sub
//参考的数据显示代码:
    Private Sub xDataGridView_CellValueNeeded(sender As Object, e As System.Windows.Forms.DataGridViewCellValueEventArgs) Handles xDataGridView.CellValueNeeded
        If (mHalt) Then
            Return
        End If
        If (e.RowIndex < 0 OrElse e.RowIndex > _ExtendList.Count) Then
            Return
        End If
        If (e.RowIndex = _ExtendList.Count AndAlso pInitData IsNot Nothing) Then
        '显示新行的代码
            Select Case e.ColumnIndex
                Case xColumnTitle.Index
                    e.Value = pInitData.mTitle
                Case xColumnValue.Index
                    e.Value = pInitData.mValue
            End Select
        ElseIf (e.RowIndex < _ExtendList.Count) Then
            With _ExtendList
                Select Case e.ColumnIndex
                    Case xColumnTitle.Index
                        e.Value = .Item(e.RowIndex).mTitle
                    Case xColumnValue.Index
                        e.Value = .Item(e.RowIndex).mValue
                End Select
            End With
        End If
    End Sub
    Private Sub xDataGridView_CellValuePushed(sender As Object, e As System.Windows.Forms.DataGridViewCellValueEventArgs) Handles xDataGridView.CellValuePushed
        If (mHalt) Then
            Return
        End If
        If (e.RowIndex < 0 OrElse e.RowIndex >= _ExtendList.Count) Then
            Return
        End If
        With _ExtendList(e.RowIndex)
            Try
                Select Case e.ColumnIndex
                    Case xColumnTitle.Index
                        .mTitle = e.Value
                    Case xColumnValue.Index
                        .mValue = e.Value
                End Select
                .raiseValueChangedEvent(_ExtendList, EventArgs.Empty)  //触发列表变化事件
            Catch exp As Exception
                MyHub.mBase.mDebugLog.writerError(Me, exp)
            Finally
            End Try
        End With
    End Sub
     '列表变化事件,此处只要根据实际数据,设置行数即可
     Private Sub listChanged(sender As Object, ByVal e As DBListChangedEventArgs(Of OuterExtendItem))
        If (Me.InvokeRequired) Then
            Me.BeginInvoke(New EventHandler(Of DBListChangedEventArgs(Of OuterExtendItem))(AddressOf listChanged), New Object() {sender, e})
        Else
            xDataGridView.RowCount = _ExtendList.Count + 1   //行数+1行
            xDataGridView.Refresh()
        End If
    End Sub
RowsAdded事件,此事件是指在表格增加新行时触发,在初始化数据增加新行和后期编辑增加新行时都会触发此事件,而UserAddedRow事件一般是指在编辑阶段由用户操作触发的增加新行事件,二者有所区别,UserAddedRow事件使用率会比较高一点,RowsAdded事件适用于产生一些根据绑定数据需要额外显示的信息时。

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