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CellStyleSelector : when changing the value, the styleselector is not called

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GridView

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answered on 08 Sep 2010, 08:39 AM

Hi,

I cannot send you my project, but you can try a simple thing :

Create a person class with Name, Age properties.
Create a personFactory to create an observablecollection(of person) filled with some new objects.
Create a radgrid view in your main.xaml like this :

<UserControl.Resources>

<local:MyStyleSelector x:Key="CellStyleSelector" />

</UserControl.Resources>

<Grid x:Name="LayoutRoot" Background="White">

<my:RadGridView ItemsSource="{Binding MyListeOfPersons}" AutoGenerateColumns="False">

<my:RadGridView.Columns>

<my:GridViewDataColumn DataMemberBinding="{Binding Name}" />

<my:GridViewDataColumn DataMemberBinding="{Binding Age}" CellStyleSelector="{StaticResource CellStyleSelector}" />

</my:RadGridView.Columns>

</my:RadGridView>

</Grid>

And here is the StyleSelector :

Public Class MyStyleSelector

Inherits StyleSelector

Public Overrides Function SelectStyle(ByVal item As Object, ByVal container As System.Windows.DependencyObject) As System.Windows.Style

Dim style As New Style(GetType(GridViewCell))

Dim cell As GridViewCell = container

Dim p As Person = item

If p.Age > 18 Then

If Application.Current.Resources.Contains("CMN_OrangeBackground") Then

style.Setters.Add(New Setter(GridViewRow.BackgroundProperty, CType(Application.Current.Resources("CMN_OrangeBackground"), Brush)))

End If

Return style

End Function

End Class

The style :

<LinearGradientBrush x:Key="CMN_OrangeBackground" EndPoint="0.5,1" StartPoint="0.5,0">

<GradientStop Color="#FFFFE3C6" />

<GradientStop Color="#FFFFC082" Offset="0.394" />

<GradientStop Color="#FFFFC68C" Offset="0.417" />

<GradientStop Color="#FFFFDB91" Offset="1" />

</LinearGradientBrush>

All the notify property changed events are raised in properties setters (on in each person property, and one in the MyListOfPersons property).

So if you try this, you will see some cells with an orange color and others without.
But, if you change the age of a person directly into the radgridview, and validate your row change by typing on enter key, you will see that the style selector is not called.

Thanks
Regards

Steeve

answered on 13 Sep 2010, 01:41 PM

Hello LE DREAU Steeve,

Please excuse me for the delayed answer. Your query provoked a small discussion in the team ,

Here is the situation in general :
The current implementation of RadGridView will not call the style selector on changes of the values( even if INotifyPropertyChanged is implemented) .

The behavior is the same as in the MS datagrid and thus might be called "expected behavior" .

Indeed having the RadGridView update the style on property changes is reasonable expectation . We were thinking to implement this in RadGridView. However we found this would imply significant performance problems. Therefore we have decided not yet to implement it.

As a workaround I may suggest to call the RadGridView.Rebind() method after the value has been changed . This should force regeneration of the UI and the style will be applied.

Best wishes,
Pavel Pavlov
the Telerik team

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answered on 21 Sep 2010, 07:00 AM

I have also had this same issue, but calling Rebind had a lot of unwanted side effects.

In my case I wanted to refresh the whole column's cells' styles so I used the following after editing a cell's contents which worked perfectly:

foreach (var item in ParametersGridView.Items)

{

var row = ParametersGridView.ItemContainerGenerator.ContainerFromItem(item) as GridViewRow;

if (row != null)

{

var otherCell = row.Cells.FirstOrDefault(x => x.Column == column) as GridViewCell;

if (otherCell != null)

{

otherCell.Style = cell.Column.CellStyleSelector.SelectStyle(otherCell.ParentRow.Item, otherCell);

otherCell.Content = column.CreateCellElement(otherCell, row.Item);

}

Might be useful to do something like this in your case...