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) Then
            Return
        End If
        pInitData = New OuterExtendItem()
        pInitData.mTitle = ""
        pInitData.mValue = ""
    End Sub

官方说明：https://msdn.microsoft.com/zh-cn/library/system.windows.forms.datagridview.newrowneeded(VS.80).aspx

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
        Else
            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。