[Solved] IsReadOnlyBinding with derived classes in hierarchy

[Jay]

I came across an annoying bug in the RadTreeListView this morning!

If I have a class hierarchy similiar to:

public abstract class Person
{
    public string Name { get; set; }
    public decimal Sales { get; set; }
    public bool IsReadOnly { get; set; }
    public abstract string Type { get; }
    private readonly ObservableCollection<Person> _people = new ObservableCollection<Person>();
    public ObservableCollection<Person> People { get { return _people; } }
}
public class Employee : Person
{
    public Employee() { IsReadOnly = true; }
    public override string Type { get { return "Employee"; } }
}
public class Client : Person
{
    public override string Type { get { return "Client"; } }
}

With Xaml similiar to:

<telerik:RadTreeListView Name="radTreeListView1" AutoGenerateColumns="false" >
            <telerik:RadTreeListView.ChildTableDefinitions>
                <telerik:TreeListViewTableDefinition ItemsSource="{Binding People}" />
            </telerik:RadTreeListView.ChildTableDefinitions>
            <telerik:RadTreeListView.Columns>
                <telerik:GridViewDataColumn DataMemberBinding="{Binding Name}" Header="Name" IsReadOnlyBinding="{Binding IsReadOnly}" />
                <telerik:GridViewDataColumn DataMemberBinding="{Binding Type}" Header="Type" IsReadOnlyBinding="{Binding IsReadOnly}" />
                <telerik:GridViewDataColumn DataMemberBinding="{Binding Sales}" Header="Sales" IsReadOnlyBinding="{Binding IsReadOnly}" />
                <telerik:GridViewDataColumn DataMemberBinding="{Binding IsReadOnly}" Header="IsReadOnly" IsReadOnlyBinding="{Binding IsReadOnly}" />
            </telerik:RadTreeListView.Columns>
        </telerik:RadTreeListView>

Using this code, I get an exception when I try to edit Joe, Sam, George, or Frank:

public partial class MainPage : UserControl
{
    public MainPage()
    {
        InitializeComponent();
        var list = new ObservableCollection<Person>();
        Employee sam = new Employee() { Name = "Alice" };
        list.Add(sam);
        sam.People.Add(new Client() { Name = "Joe" });
        sam.People.Add(new Client() { Name = "Sam" });
        Employee john = new Employee() { Name = "John" };
        john.People.Add(new Client() { Name = "George" });
        john.People.Add(new Client() { Name = "Frank" });
        list.Add(john);
        //list.Add(new Client() { Name = "Jay" });
        radTreeListView1.ItemsSource = list;
    }
}

However if I use the following code:

public partial class MainPage : UserControl
{
    public MainPage()
    {
        InitializeComponent();
        var list = new ObservableCollection<Person>();
        Employee sam = new Employee() { Name = "Alice" };
        list.Add(sam);
        sam.People.Add(new Client() { Name = "Joe" });
        sam.People.Add(new Client() { Name = "Sam" });
        Employee john = new Employee() { Name = "John" };
        john.People.Add(new Client() { Name = "George" });
        john.People.Add(new Client() { Name = "Frank" });
        list.Add(john);
        list.Add(new Client() { Name = "Jay" });
        radTreeListView1.ItemsSource = list;
    }
}

I don't get the exception.

Notice the only difference is I included both derived classes in the root collection in the working case, where as there was only a single derived class in the failing case. 

The exception I am receiving is "Unable to cast object of type 'SilverlightApplication5.Client' to type 'SilverlightApplication5.Employee'."

The stack trace is: 

at Telerik.Windows.Data.FuncExtensions.<>c__DisplayClass1`2.<ToUntypedFunc>b__0(Object item)
at Telerik.Windows.Controls.GridViewBoundColumnBase.EvaluateIsReadOnlyState(Object item)
at Telerik.Windows.Controls.GridViewBoundColumnBase.CanEdit(Object item)
at Telerik.Windows.Controls.GridView.GridViewDataControl.BeginEdit(GridViewCell gridViewCell, RoutedEventArgs editingEventArgs)
at Telerik.Windows.Controls.GridView.GridViewDataControl.OnCellMouseDown(GridViewCell cell, MouseButtonEventArgs args)
at Telerik.Windows.Controls.GridView.GridViewCell.OnMouseLeftButtonDown(MouseButtonEventArgs e)
at System.Windows.Controls.Control.OnMouseLeftButtonDown(Control ctrl, EventArgs e)
at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)

One workaround I thought of was to included the second derived class for binding, then remove the second item right away, similar to:

Client jay = new Client() { Name = "Jay" };
list.Add(jay);
radTreeListView1.ItemsSource = list;
list.Remove(jay);

However that doesn't appear to work...

A second more viable option might be a strategy pattern where there is only  a single class in the grid, but this class delegates to the various derived classes. A "hack" but it should work.

Any thoughts?

In my actual use case there will only be one derived class in the grid's root, then a plethora of derived classes down the hierarchy of the grid...

Thanks
Jay




 

[Jay]

I should add this is with version 2011.1.419.1040 of the controls.

Thanks
Jay

[Yordanka]

Hi Jay,

We are currently investigating the problem and we will contact you as soon as we have more information.
 
Best wishes,
Yordanka
the Telerik team

[Yordanka]

Hi Jay,

The problem is already resolved and the fix for it is included in our Q2 2011 official version.
 
Kind regards,
Yordanka
the Telerik team

[Carson]

{
    public string Name{get;set;}
    public ViewType Type {get;set;}

}

The Above Class is the my base view model that is being displayed in the grid.

I derive several other VM from this one and Bind a grid to them

public class PersonViewModel:ViewModel
{
  public string State{get;set;}
}

public class AddressViewModel:ViewModel
{
  public string Street1{get;set;}
}

ObservableCollection<ViewModel> _items;

public ObservableCollection<ViewModel>
{
  get
  {
    return _items;
  }
}

The Grid is then bound to the Items property

<GridView:RadGridView
              ItemsSource="{Binding Items}"
              CanUserFreezeColumns="False"
              ScrollMode="RealTime"
              IsReadOnly="True"
              x:Name="AlertGrid" IsFilteringAllowed="False"
              GridLinesVisibility="None" AutoGenerateColumns="False"
              MinHeight="350" MaxHeight="525"
              RowStyle="{StaticResource rowStyle}">
              <GridView:RadGridView.Columns>
                  <GridView:GridViewDataColumn Header="Name" SortingState="Descending" DataMemberBinding="{Binding Name}" Width="150" IsFilterable="False"/>
                  <GridView:GridViewDataColumn Header="ViewType" DataMemberBinding="{Binding Type}" Width="150" IsFilterable="False"/>
                       </GridView:RadGridView.Columns>
          </GridView:RadGridView>

When I first load the ites everything in the collection are just PersonViewModel and they display fine. If I group on a property of the base type i.e. ViewModel.Name It will group just fine. However if while grouped I add a new item to the collection that is an AddressViewModel then I get an exception that looks like

The value "AddressViewModel" is not of type "PersonViewModel" and cannot be used in this generic collection.

If I however ungroup the grid and then add the AddressViewModel to the collection and then regroup, it all works as expected and I don't recieve an error.

Understand that my problem has been paraphrased and these are not the exact object names nor fields that I am using in the application, but hopefully describes my problem well enough.

I am using 2011.2.712.1040 of the Grid Controls\


Edit: Just Relized that I posted in the wrong forum, but the issues seem related. If not I will repost in the grid forum