Exploring MVVM: Grouping with the DataGrid

Windows 7 News » Exploring MVVM: Grouping with the DataGrid

Windows 7 News » Exploring MVVM: Grouping with the DataGrid — Thu, 22 Jan 2009 03:46:48 GMT

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re: Exploring MVVM: Grouping with the DataGrid

Thibaud — Sun, 01 Feb 2009 20:14:52 GMT

Your article just give me an idea

While {Binding} linking controls to data, my {MethodBinding} linking controls to a public method on Data entity

see more here :

http://thibaud60.blogspot.com/2009/02/convert-clr-method-to-icommand-with.html

Performance Issues

Alexander — Tue, 10 Feb 2009 20:00:44 GMT

Dear Vincent,

maybe you are not the right one to address for this issue, but maybe you could give me a hint. We use the WPF CTP Datagrid for a set of ~50 records (14 columns). Since the records increased from a few to the mentioned 50, in-cell editing became unbelievably slow, i.e. it takes seconds for the characters to appear after the key was pressed.

The (well maybe not so) funny thing is that this occurs only on 64-bit, Windows Vista Home Premium HP TouchSmart with 4 GB of RAM and Intel DualCore CPU. The behaviour does not occur on slower 32bit-machines (we dont have an extra 64-bit machine to test). The WPF Visual Profiler shows that there is a lot of time spent for "Layout". Whatever that means -- since it does not occur while editing on the 'not so good' machines. We do not hook onto any Datagrid-specific events, editing messages or whatsoever.

Most remarkable to us was the fact that edit controls placed on a window which is child of the window containing the Datagrid show the same behaviour.

Do you have any hint for us?

Best Regards,

Alexander

re: Exploring MVVM: Grouping with the DataGrid

Alexander — Thu, 12 Feb 2009 19:04:50 GMT

Hi, this is Alexander again.

I solved the problem, but without knowing what the reason was. I found out that the problem did not occur when I removed the columns with the "IsReadOnly"-property set to "True". To work around using this property, I used a DataGridTemplateColumn with a DataGrid.CellTemplate and a TexBlock in it, but without a DataGrid.CellEditingTemplate. That was it. Now my customer is happy again. But still, this behaviour seems pretty strange to me.

For people facing the same problem, here is a small before/after-XAML-snippet:

BEFORE (slow):

==============

<dg:DataGridTextColumn

Header="Test-Column"

IsReadOnly="True"

Binding="{Binding Path=a_usual_read_only_property}"

CanUserSort="False"/>

AFTER (as it should be):

========================

<dg:DataGridTemplateColumn Header="Test-Column">

<dg:DataGridTemplateColumn.CellTemplate>

</DataTemplate>

</dg:DataGridTemplateColumn.CellTemplate>

</dg:DataGridTemplateColumn>

re: Exploring MVVM: Grouping with the DataGrid

shafique — Thu, 03 Sep 2009 18:46:15 GMT

I'm trying to set the Command binding from within a DataGridTemplateColumn, like so:

<toolkit:DataGridTemplateColumn>

<toolkit:DataGridTemplateColumn.CellTemplate>

<TextBlock.ContextMenu>

<MenuItem x:Name="Assign" Header="Assign"

mvvm:CommandBehavior.Event="Click"

mvvm:CommandBehavior.Command="{Binding Path=DataContext.EditLabelCommand, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type UserControl}}}"

mvvm:CommandBehavior.CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContextMenu}}, Path=DataContext}"/>

</ContextMenu>

</TextBlock.ContextMenu>

</TextBlock>

</DataTemplate>

</toolkit:DataGridTemplateColumn.CellTemplate>

</toolkit:DataGridTemplateColumn>

but I can't find the binding source. Any ideas? I'm trying to hookup a EditCommand on my viewmodel, which is the datacontext for this usercontrol.

re: Exploring MVVM: Grouping with the DataGrid

vinsibal — Tue, 08 Sep 2009 16:38:35 GMT

shafique,

What does the binding error say, that it cannot find UserControl? Have you tried specifying your specific implementation of the UserControl?

re: Exploring MVVM: Grouping with the DataGrid

Frank — Tue, 08 Dec 2009 09:31:21 GMT

Vincent

in your example you put an IsExpanded property directly on each of the items.

I have a similar problem, by which each item in the collection is styled depending on the actual data of the item. ( with many different style elements like typeface, color, size, IsExpanded ... ). I hesitate to clutter up the model with this type of data.

I wonder if in the spirit of MVVM I should implement this with value converters or if it is not better to have the ItemSource bind to a collection of ItemViewModels which provides the style data and references the items data

Frank

re: Exploring MVVM: Grouping with the DataGrid

vinsibal — Tue, 15 Dec 2009 13:02:36 GMT

Frank,

Style data is really a View concept and while some properties make sense to bind to, not all of them should be bound to the ViewModel.