EntitySpaces Version # 2007.0.0730.0
MyGeneration Version # 1.2.0.7

Language: VB.NET

Using the Infragistics WinGrid with EntitySpaces leads sometimes to let's say interesting issues. Using VB.NET does the rest...

Bounding an EntityCollection to WinGrid and deleting the value of a cell, results in a DBNull-Value for that cell. Since in VB we need the value Nothing, you get permanent errors like "Unable to update the data value: The object with the type System.DBNull can not be converted to the type System.String.". (I've tried to translate the message...)

To get around this issue, you have to switch DBNull into Nothing.

    Private _DBNullToNothingCell As UltraGridCell = Nothing

    Private Sub uxGrid_BeforeCellUpdate(ByVal sender As Object, ByVal e As Infragistics.Win.UltraWinGrid.BeforeCellUpdateEventArgs) Handles uxGrid.BeforeCellUpdate
        If IsDBNull(e.NewValue) Then _DBNullToNothingCell = e.Cell
    End Sub

    Private Sub uxGrid_CellDataError(ByVal sender As Object, ByVal e As Infragistics.Win.UltraWinGrid.CellDataErrorEventArgs) Handles uxGrid.CellDataError
        If _DBNullToNothingCell IsNot Nothing Then
            e.RaiseErrorEvent = False
            e.RestoreOriginalValue = False
            e.StayInEditMode = False
            _DBNullToNothingCell.Value = Nothing
            _DBNullToNothingCell = Nothing
        End If
    End Sub

The reason why I use the variable DBNullToNothingCell and not ActiveCell in CellDataError is, that in some circumstances ActiveCell ist not always the same. Furthermore it is not possible to change the value of the cell in BeforeCellUpdate. That's why I'm doing it in the CellDataError-Event.

I'm sure there is a more elegant solution out there, and I'm definitly interested in it. Maybe I've missed something in ES, so that I could avoid using these events. But on the other hand, if some else is just struggling with this issue, here are my 2 Cents how you can deal with it.

BTW, I've just started using EntitySpaces again for a current project - after using it on the same project about one year ago. I really have to say that it is a lot of fun working with it again. I think you - the ES Team - are really doing a great job.

Thanks for a great product!

Hmm, after reading the following post
Possible Defect: Updating to blank string in grid using esDataSource
I wonder if it shouldn't also be possible with the Infragistics Grid to get it to work without the events mentioned above?

Infragistics Grid seems to implicitly use the underlying type System.String, which doesn't allow DBNull but Nothing. The error gets fired by the Grid itself. So the following code in ES wouldn't be called in this case:

 
Code:
    Public Overrides Sub SetProperty(name as string, value as object)
            
                If Not Me.Row Is Nothing Then
       
                    Dim col As esColumnMetadata = Me.Meta.Columns.FindByPropertyName(name)
                    If Not col Is Nothing Then
                    
                       If value Is Nothing OrElse value.GetType().ToString() = "System.String" Then

Of course it does work with datasets without any problems. How can I get it to work with ES?

I've forgotten to mention, that I've tried this:

  Public Overrides Sub SetProperty(name as string, value as object)

    	If Me.Row Is Nothing Then
	  Me.AddNew()
    	End IF
    			
	Dim col As esColumnMetadata = Me.Meta.Columns.FindByPropertyName(name)
                If Not col Is Nothing Then
   
                   If IsDBNull(value) Then value = Nothing
   
                   If value Is Nothing OrElse value.GetType().ToString() = "System.String" Then
   

But since the Grid checks the data type by itself the error gets thrown there and the code above is not called anyway.

Nevertheless if the value equals DBNull in VB, I think changing it to Nothing in SetProperty makes sense, doesn't it? Unless I've completely missed something maybe this should be done in your VB templates?

BTW, you could improve your generated VB code by generally using AndAlso instead of And and OrElse instead of Or.

Oh no, it's so easy...!

Just use the following code (for example in the InitializeLayout Event):

For Each column As UltraGridColumn In grid.Rows.Band.Columns
    column.Nullable = Nullable.Nothing
Next

With the Nullable property you can define how UltraGrid store Null values. The list below shows all possible values for Nullable:

Nevertheless there is a need to react on MultiCellOperations. In case of a MultiCellOperation like Cut, Copy or Delete, UltraGrid seems not to use the Nullable property. Here's my solution for that scenario:

Private Sub uxGrid_BeforeMultiCellOperation(ByVal sender As Object, ByVal e As Infragistics.Win.UltraWinGrid.BeforeMultiCellOperationEventArgs) Handles uxtGrid.BeforeMultiCellOperation
    Dim isPasteOperation As Boolean = (e.Operation = MultiCellOperation.Paste)
    If e.Operation = MultiCellOperation.Delete OrElse e.Operation = MultiCellOperation.Cut OrElse isPasteOperation Then
        For rowIndex As Integer = 0 To e.Cells.RowCount - 1
            For colIndex As Integer = 0 To e.Cells.ColumnCount - 1
                If isPasteOperation Then
                    If IsDBNull(e.NewValues(e.Cells.Item(rowIndex, colIndex)).Value) OrElse _
                       e.NewValues(e.Cells.Item(rowIndex, colIndex)).Value.ToString = "" Then
                        e.NewValues(e.Cells.Item(rowIndex, colIndex)).Value = Nothing
                    End If
                Else
                    e.NewValues(e.Cells.Item(rowIndex, colIndex)).Value = Nothing
                End If
            Next
        Next
     End If
End Sub

Again I could imagine that there exists a better solution. But I couldn't find any, so maybe this can be also usefull for others using the UltraGrid.

I appreciate the post, this has certainly saved me some time digging for an answer.

I'm glad it was of any help for you.

Thanks for your feedback!

Nice one! Saved me a lot of arsing around with that.