How to hide rows bound to GridView?

[Rob Ainscough]

I'm trying to setup a GridView that will hide (not visible) rows (objects) based on some of my own criteria.  A checkbox external to the GridView will drive the logic that makes these rows visible or hidden.

I assume I can do this one of two way:

1.  Setup a filter and apply the filter to the Grid?
2.  LoadingRowDetails and somehow set visibility of row?

I'm sure this is a very common scenario, can someone give me hints/ideas on how to accomplish this using MVVM?

EDIT: Tried to setup and bind a filter value, but that doesn't seem to work (grid is not being filter) ...

<telerik:RadGridView.FilterDescriptors>
<telerik:FilterDescriptor
Member="CustomerUnitStatus"
Operator="IsEqualTo"
Value="{Binding Path=UnitStatusFilter, Mode=TwoWay, FallbackValue='Occupied', TargetNullValue='Occupied'}"
IsCaseSensitive="False"/>

</telerik:RadGridView.FilterDescriptors>

In my MVVM I have a UnitStatusFilter property I'm still seeing rows in the GridView that are NOT equal.  IsFilteringAllowed=True for the GridView

Thanks, Rob.

[Rossen Hristov]

Hi,

Since the FilterDescriptor is not part of the visual tree you cannot bind it like that in XAML, since its DataContext is not the same as the one of the grid.

Create a FilterDescriptor in code behind and add it to the FilterDescriptors collection. Kepp its reference. Attach to the PropertyChanged event of your view model and if the changed property is UnitStatusFilter update the FilterDescriptor.Value. Note that the Value you set must be of the same type as the data in the column. 

I am afraid that this cannot be done entirely through XAML. If you don't want to leave your MVVM pattern you can always embed this code in an attached behavior and set it on the grid.

More about programmatic filtering you can learn here.

Regards,
Rossen Hristov
Telerik

[Rob Ainscough]

Can you point me to a code sample (including XAML) for attached behavior?  The link you provided appears to be all code behind.

Thanks, Rob.

[Rob Ainscough]

UPDATE:

I tried using Code Behind, but the filtering is still not happening. I stepped thru the code behind and I can see the data in the Me.UnitSelectionGridView (data binding is happening) and the Filter is added, but the filtering just doesn't seem to work.

My code behind:

Private Sub DCUnitSelectionGrid_Loaded(sender As Object, e As RoutedEventArgs) Handles Me.Loaded

    Me.UnitSelectionGridView.FilterDescriptors.SuspendNotifications()
    Dim UnitFilter As New Telerik.Windows.Data.FilterDescriptor("Balance", Telerik.Windows.Data.FilterOperator.IsEqualTo, 0)
    Me.UnitSelectionGridView.FilterDescriptors.Add(UnitFilter)
    Me.UnitSelectionGridView.FilterDescriptors.ResumeNotifications()

End Sub

[Rob Ainscough]

I have this "partially working" using a behavior - XAML:

<telerik:RadGridView x:Name="UnitSelectionGridView" AreRowDetailsFrozen="True" AutoGenerateColumns="False" CanUserFreezeColumns="False" CanUserReorderColumns="False" CanUserResizeColumns="False" CanUserSortColumns="False" RowIndicatorVisibility="Collapsed" IsReadOnly="False" ShowGroupPanel="False" IsFilteringAllowed="True"
                ItemsSource="{Binding Path=Customer.CustomerUnits}">

    <i:Interaction.Behaviors>
        <DC:RadGridViewGenericFilter x:Name="UnitSelectionFilter" ColumnMember="CustomerUnitStatus" LogicOperator="IsEqualTo"  FilterValue="1" />
    </i:Interaction.Behaviors>

and the behavior code:

Imports System.Windows.Interactivity
Imports Microsoft.Expression.Interactivity

Public Class RadGridViewGenericFilter
    Inherits Behavior(Of Telerik.Windows.Controls.RadGridView)

    ' NOTE: ColumnMember = DataMemberBinding value (not the column header)
    Private _ColumnMember As String
    Public Property ColumnMember() As String
        Get
            Return _ColumnMember
        End Get
        Set(ByVal value As String)
            _ColumnMember = value
        End Set
    End Property

    Private _LogicOperator As Telerik.Windows.Data.FilterOperator
    Public Property LogicOperator() As Telerik.Windows.Data.FilterOperator
        Get
            Return _LogicOperator
        End Get
        Set(ByVal value As Telerik.Windows.Data.FilterOperator)
            _LogicOperator = value
        End Set
    End Property

    Private _FilterValue As String
    Public Property FilterValue() As String
        Get
            Return _FilterValue
        End Get
        Set(ByVal value As String)
            _FilterValue = value
        End Set
    End Property

    Protected Overrides Sub OnAttached()
        MyBase.OnAttached()

        If Not String.IsNullOrEmpty(ColumnMember) Then

            AddHandler AssociatedObject.DataLoading, AddressOf AssociatedObject_DataLoading

        End If

    End Sub

    Protected Overrides Sub OnDetaching()
        MyBase.OnDetaching()

        RemoveHandler AssociatedObject.DataLoading, AddressOf AssociatedObject_DataLoading

    End Sub

    Private Sub AssociatedObject_DataLoading(sender As Object, e As Telerik.Windows.Controls.GridView.GridViewDataLoadingEventArgs)

        If AssociatedObject.FilterDescriptors.Count = 0 Then

            Dim CustomerUnitStatusColumn As Telerik.Windows.Controls.GridViewColumn = AssociatedObject.Columns(ColumnMember)
            Dim columnDescriptor As Telerik.Windows.Controls.GridView.IColumnFilterDescriptor = CustomerUnitStatusColumn.ColumnFilterDescriptor

            With columnDescriptor
                .SuspendNotifications()
                .FieldFilter.Filter1.Operator = LogicOperator
                .FieldFilter.Filter1.Value = FilterValue
                .ResumeNotifications()
            End With

        End If

    End Sub

End Class

So far so good, ColumnFilterDescriptor is setup, Data loads and is filtered.  All MVVM - this is good.  Now, the part I'm stuck at ... how do I set the FilterValue property in my Behavior so that GridView will get updated and display data based on new filter value -- and do this thru my MVVM class?  There is no binding to behavior properties, not supported in SL5, so what are my options? 

Thanks, Rob.

[Rossen Hristov]

Hello,

I have the following idea.

AssociatedObject is the grid, right. So we have a reference to the grid. From the original binding that you tried to use, I suppose that the DataContext of the grid is an instance of your view model. So what you can do is cast the grid's DataContext property to your view model class. Now you will have a reference to the view model that is the DataContext of the grid, where you can subsribe to its PropertyChanged event and when the respective property changes (I think it was called UnitStatusFilter) -- update the Value of the descriptor. And all of this will be nicely tucked away in the behavior and you will not see it in XAML.

Or simply add another property to the behavior class and somehow pass the instance of the view model there. I am not sure whether this is possible in SL though.

There might be other possible approaches to "feeding" a behavior with additional information, i.e. a reference to something that the behavior needs. I suppose that the guys on StackOverflow might have more clever ideas about this task.

Regards,
Rossen Hristov
Telerik