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GridViewDataColumn Header from RIA MetaData?

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answered on 07 Sep 2009, 10:18 PM

Hi Vlad,

Yes, if your grid is implemented the same way as the MS SL3 RTM DataGrid, that will be excellent. The MS DataGrid code in the snippet below results in the Headers automatically being populated from the DisplayAttribute in our meta data--no Header="..." required. We are going to generate meta data from a localised meta-data provider, and the auto-populated Header behaviour would greatly reduce the number of places we need to explicitly provide a localised Header.

    
                    <DataControls:DataGrid x:Name="ListDataGrid" 
        
                                            ItemsSource="{Binding Path=BookingItemsSource}" 
        
                                            SelectedItem="{Binding SelectedBooking, Mode=TwoWay}" 
        
                                            Width="Auto" 
        
                                            Height="Auto" 
        
                                            AutoGenerateColumns="False" 
        
                                            SelectionMode="Single" 
        
                                            HeadersVisibility="All" 
        
                                            CanUserResizeColumns="True" 
        
                                            CanUserReorderColumns="True" 
        
                                            CanUserSortColumns="True" 
        
                                            HorizontalScrollBarVisibility="Auto" 
        
                                            VerticalScrollBarVisibility="Visible" 
        
                                            VerticalContentAlignment="Top" 
        
                                            IsReadOnly="True" 
        
                                            > 
        
                        <DataControls:DataGrid.Columns> 
        
                            <DataControls:DataGridTextColumn  Binding="{Binding book_id}" /> 
        
                            <DataControls:DataGridTextColumn  Binding="{Binding book_summary}" /> 
        
                            <DataControls:DataGridTextColumn  Binding="{Binding book_start}" /> 
        
                            <DataControls:DataGridTextColumn  Binding="{Binding book_end}" /> 
        
                            <DataControls:DataGridTextColumn  Binding="{Binding Job}" /> 
        
                            <DataControls:DataGridTextColumn  Binding="{Binding CostCentre}" /> 
        
                            <DataControls:DataGridTextColumn  Binding="{Binding Priority}" /> 
        
                            <DataControls:DataGridTextColumn  Binding="{Binding book_actual_end}" /> 
        
                            <DataControls:DataGridTextColumn  Binding="{Binding Address}" /> 
        
                        </DataControls:DataGrid.Columns> 
        
                    </DataControls:DataGrid>

Cheers,
Scott

answered on 08 Sep 2009, 06:01 AM

silverlightapplication.zip

Hello Scott,

I've tried MS DataGrid with declared columns however this didn't worked for me - I've attached small project.

Best wishes,
Vlad
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answered on 08 Sep 2009, 10:48 PM

Hi Vlad,

Interesting! It appears to be the DomainDataSource that makes the difference. If you bind the DataGrid's ItemsSource directly to the RIA DomainContext's .Customers (EntityList<Customer>) property (as we are doing in our solution using a MVVM pattern), the Headers get auto-populated from the DisplayAttribute. If the DataGrid is bound to an intermediate DomainDataSource, the Headers are lost.

I've updated your sample project with a example of what I mean. Can I upload here?

Basically the altered sample looks like this:

MainPage.xaml (Note the DataGrid1.ItemsSource binding):

    
            ﻿<UserControl x:Class="SilverlightApplication.MainPage" 
        
                xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"  
        
                xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
        
                xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"  
        
                xmlns:web="clr-namespace:WebApplication" 
        
                xmlns:ria="clr-namespace:System.Windows.Controls;assembly=System.Windows.Ria.Controls" 
        
                xmlns:data="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Data" 
        
                xmlns:telerikInput="clr-namespace:Telerik.Windows.Controls;assembly=Telerik.Windows.Controls.Input" 
        
                xmlns:telerikGridView="clr-namespace:Telerik.Windows.Controls;assembly=Telerik.Windows.Controls.GridView" 
        
                mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480"> 
        
                <Grid x:Name="LayoutRoot"> 
        
            <!--        <ria:DomainDataSource x:Name="DomainDataSource1" AutoLoad="True" QueryName="GetCustomers">--> 
        
            <!--            <ria:DomainDataSource.DomainContext>--> 
        
            <!--                <web:DomainService1 />--> 
        
            <!--            </ria:DomainDataSource.DomainContext>--> 
        
            <!--        </ria:DomainDataSource>--> 
        
                    <data:DataGrid x:Name="DataGrid1" ItemsSource="{Binding Customers, Mode=OneWay}" 
        
             Width="Auto" Height="Auto" AutoGenerateColumns="False" SelectionMode="Single" HeadersVisibility="All"  
        
             CanUserResizeColumns="True" CanUserReorderColumns="True" CanUserSortColumns="True" HorizontalScrollBarVisibility="Auto"  
        
             VerticalScrollBarVisibility="Visible" VerticalContentAlignment="Top" IsReadOnly="True"> 
        
                        <data:DataGrid.Columns> 
        
                            <data:DataGridTextColumn Binding="{Binding Address}" /> 
        
                            <data:DataGridTextColumn Binding="{Binding City}" /> 
        
                        </data:DataGrid.Columns> 
        
                    </data:DataGrid> 
        
                </Grid> 
        
            </UserControl>

MainPage.xaml.cs:

    
            namespace SilverlightApplication 
        
            { 
        
                public partial class MainPage : UserControl 
        
                { 
        
                    private WebApplication.DomainService1 _domainServiceClient; 
        
                    public MainPage() 
        
                    { 
        
                        InitializeComponent(); 
        
                        _domainServiceClient = new WebApplication.DomainService1(); 
        
                        DataContext = _domainServiceClient; 
        
                        _domainServiceClient.Load(_domainServiceClient.GetCustomersQuery()); 
        
                    } 
        
                } 
        
            }

So I know it would make us happy if the RadGridView worked as the DataGrid does above, but I don't know how many others will use it in this way (binding directly to EntityList). Let me know if you want to see the whole modified test solution.

Cheers,
Scott

answered on 18 Oct 2009, 06:14 PM

How was this implemented by Telerik? Does is retrieve the [Display] information of a relevant property via an instance of the object in context? If yes, then this has the same flaw as the default DataForm in Silverlight: If there is no instance, i.e. if the collection bound to the grid is empty, then there won't be any column headers displayed. The same goes for the DataForm: it becomes quite invisible, when there's no instance to bind to. This constitutes a major UI flaw - but I don't know how to fix this either, without resorting to explicitely binding the headers to localized resources.

Regards,
Kasimier

answered on 22 Oct 2009, 09:23 AM

Hello Kasimier,

We try to resolve the type, which donates the attributes on several step. First we check to see if you have passed a generic enumerable as ItemsSource if so we take its type. If the type is object (rear cases when you bind to IEnumerable<object>) we resolve the type from the first instance. If you have passed a non generic collection we also fall back to resolve the type from the first element.

Hope this helps.

Sincerely yours,
Stefan Dobrev
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answered on 25 Jan 2010, 11:31 AM

It sounds great but it's not working like MS Datagrid, at least not in my version (using SP2).

I'm binding my itemssource property to a collection that implements IEnumerable<T>, ICollectionView and IPagedCollectionView. The items in the collection are entities from WCF RIA Services and they have DisplayAttribute applied to its properties.

When the view loads the collection is empty (not null, just empty) and then I fetch my data asynchronously (using WCF RIA Services), the collection gets items added to it (INotifyCollectionChanged event fires) and only then the headers are displayed.

The problem is that (besides the delay when displaying the headers) is that in some cases I might not have data to display and the grid will not show any headers at all..

With MS Datagrid the headers are automatically displayed when the view loads, even if the collection is empty, so when my data is fetched the grid already has the headers displayed, even if there is no data to return.

I'd really like to know if I'm doing anything wrong or if this is supposed to work with empty collections.

Best regards,

Manuel Felício

answered on 28 Jan 2010, 11:25 AM

Hello Manuel,

You have hit a corner case. The problem is that when RadGridView is bound to IPagedCollectionView it delays its columns creation until there are items in the view. We do this because we will generate columns based on the first item type in the view. However in your case we can generate columns based on the generic type of your collection, bypassing the IPagedCollectionView. We will do our best to change this behavior in one of the next internal builds of the control.

Thanks for pointing out this issue. I have updated your Telerik points.

All the best,
Stefan Dobrev
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answered on 23 Feb 2010, 11:58 PM

Stefan,
Have an observation similar to Manuel's... and a question. Two-way binding is in place on a collection in a telerikGrid in our Silverlight app.

We use 3 lines to bind (this will be a VB rendering):

Dim oCollectionViewSource As New Data.CollectionViewSource

oCollectionViewSource.Source = our_collection

grdShowCollection.ItemsSource = oCollectionViewSource.View

The grid has a dropdown but that is working fine. You called Manuel's description a corner case.

If the collection is empty, we cannot insert items into the grid that does not break the two-way binding. Is there a way to preserve the two-way binding and insert a blank row into the grid when the Source of CollectionViewSource is empty?

Keefe

answered on 24 Feb 2010, 10:42 PM

Stefan,

Thanks for your quick response. We have solved our issue and we wanted to spare others the effort by discussing the technique here. It applies to Manuel's question as well. The code we offered earlier in the thread worked for a two-way binding of a collection to a grid object, but seemed not to work when the collection was empty.

In our example we have a combo and a textbox inside our telerik grid. The combo binds a collection wonderfully using the telerik controls and the methods described. But if the collection were empty how would we preserve two-way binding and get our control to recognize new items. The clue was given by Manuel himself, although he was concerned about auto-generating the headers. When the INotifyCollectionChanged event is wired up correctly in the objects behind it will 'wake up' the control when you add a stub member to the underlying collection. All you have to do is determine the default values for the collection members and add an object to the collection. The control recognizes the internal binding and restores the column integrity (or the headers), keeping the two-way binding. This is great when several events are adding and removing items from collections that affect this collection, because you can be sure that the grid will always have the latest contents.

We spent 3 peoples' work of 2 days effort to get this right! The first big step was getting to the CollectionViewSource and understanding that implementation completely; the second was wiring up the INotifyCollectionChanged event to get the two-way binding in place and the third was realizing that if the wire-up were correct, the collection would force the controls to respond.

Hope this helps others.

Keefe

answered on 26 Apr 2010, 11:45 AM

Hello Manuel Felício,

If this is the same as this PITS issue, then it was fixed. But I am not sure that it is the same.

I would strongly recommend downloading the latest version (it's free) and testing against your specific scenario.

Please, let us know if problems still occur. It would be even better if you send us your sample project, since you might have hit another bug that is different from the one above.

Thank you in advance.

Sincerely yours,
Ross
the Telerik team

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answered on 19 Mar 2012, 03:18 PM

Does this only work with the Silverlight version of the controls? I'm trying to get this to work with the latest WPF RadGridView, and have a collection of object with DisplayAttribute set, and the collection supports IEnumerable<T> and ICollection<T>.

I have noticed that this appears to not work on the sample application for WPF or Silverlight (http://www.telerik.com/help/silverlight/gridview-columns-defining-columns.html ) . I'm trying to get this example to work, following forum posts that indicate that it is now fixed.

I'f it is working, could you please post some sample code.

Regards,

Chris.