VB-Tips

DataGrid: Raise Event When User Presses Delete Key using OS messages

To be notified when the user presses the delete key to delete a row in a datagrid you have to create a new datagrid. You must override the PreprocessMessage and the ProcessDialogKey events in the datagrid. Here is a sample class that inherits from the datagrid that raises an event when a user deletes a row. Public Class ConfirmDeleteDataGrid
    Inherits DataGrid

    Public Event DeletedRow(ByVal sender As Object, ByVal e As EventArgs)
    Private Const WM_KEYDOWN = &H100

    Public Overrides Function PreProcessMessage(ByRef msg As System.Windows.Forms.Message) As Boolean
        Dim keyCode As Keys = CType((msg.WParam.ToInt32 And Keys.KeyCode), Keys)

        If msg.Msg = WM_KEYDOWN And keyCode = Keys.Delete Then
            If MessageBox.Show("Delete This Row?", "Confirm Delete", _
              MessageBoxButtons.YesNo) = DialogResult.No Then
                Return True
            Else
                RaiseEvent DeletedRow(Me, New EventArgs)
            End If
        End If

        Return MyBase.PreProcessMessage(msg)

    End Function

    Protected Overrides Function ProcessDialogKey(ByVal keyData As System.Windows.Forms.Keys) As Boolean
        Dim pt As Point
        Dim hti As DataGrid.HitTestInfo

        pt = Me.PointToClient(Cursor.Position)
        hti = Me.HitTest(pt)

        If keyData = Keys.Delete Then
            If hti.Type = Me.HitTestType.RowHeader Then
                If MessageBox.Show("Delete this row?", "Confirm Delete", _
                   MessageBoxButtons.YesNo) = DialogResult.No Then
                    Return True
                Else
                    RaiseEvent DeletedRow(Me, New EventArgs)
                End If
            End If
        End If

        Return MyBase.ProcessDialogKey(keyData)
    End Function


End Class

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