[Solved] Sort being cleared when ItemsSource is updated.

[Chris]

I'm having a problem with the sort descriptors being cleared from the grid when my data source is updated. Here is a sample I created to recreate the problem.

<UserControl x:Class="RedHeaderTest.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"
    mc:Ignorable="d" d:DesignWidth="640" d:DesignHeight="480" xmlns:telerik="http://schemas.telerik.com/2008/xaml/presentation">
    <Grid x:Name="LayoutRoot">
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <StackPanel Orientation="Horizontal">
            <Button Content="Hookup Data" Width="Auto" Margin="4,2,4,2" Click="Button_Click"/>
        </StackPanel>
        <telerik:RadGridView Margin="5" Grid.Row="1" AutoGenerateColumns="False" x:Name="ParentGrid" ShowGroupPanel="False">
            <telerik:RadGridView.Columns>
                <telerik:GridViewDataColumn Width="100" UniqueName="Col1" DataMemberBinding="{Binding Path=Col1}">
                    <telerik:GridViewDataColumn.Header>
                        <TextBlock Text="Col1" TextAlignment="Left" HorizontalAlignment="Stretch" VerticalAlignment="Center"/>
                    </telerik:GridViewDataColumn.Header>
                </telerik:GridViewDataColumn>
                <telerik:GridViewDataColumn Width="100" UniqueName="Col2" DataMemberBinding="{Binding Path=Col2}">
                    <telerik:GridViewDataColumn.Header>
                        <TextBlock Text="Col2" TextAlignment="Left" HorizontalAlignment="Stretch" VerticalAlignment="Center"/>
                    </telerik:GridViewDataColumn.Header>
                </telerik:GridViewDataColumn>
                <telerik:GridViewDataColumn Width="100" UniqueName="Col3" DataMemberBinding="{Binding Path=Col3}">
                    <telerik:GridViewDataColumn.Header>
                        <TextBlock Text="Col3" TextAlignment="Left" HorizontalAlignment="Stretch" VerticalAlignment="Center"/>
                    </telerik:GridViewDataColumn.Header>
                </telerik:GridViewDataColumn>
                <telerik:GridViewDataColumn Width="100" UniqueName="Col4" DataMemberBinding="{Binding Path=Col4}">
                    <telerik:GridViewDataColumn.Header>
                        <TextBlock Text="Col4" TextAlignment="Left" HorizontalAlignment="Stretch" VerticalAlignment="Center"/>
                    </telerik:GridViewDataColumn.Header>
                </telerik:GridViewDataColumn>
            </telerik:RadGridView.Columns>
        </telerik:RadGridView>
    </Grid>
</UserControl>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

namespace RedHeaderTest
{
    public partial class MainPage : UserControl
    {
        private List<ParentData> _data;

        public MainPage()
        {
            this._data = new List<ParentData>();
            this._data.Add(new ParentData()
            {
                Col1 = "Row1 Col1",
                Col2 = "Row1 Col2",
                Col3 = "Row1 Col3",
                Col4 = "Row1 Col4",
                ChildData = new List<ChildData>(
                    new ChildData[] {
                        new ChildData()
                        {
                            Col1 = "ParentRow1 Row1 Col1",
                            Col2 = "ParentRow1 Row1 Col2",
                            Col3 = "ParentRow1 Row1 Col3",
                            Col4 = "ParentRow1 Row1 Col4",
                        },
                        new ChildData()
                        {
                            Col1 = "ParentRow1 Row2 Col1",
                            Col2 = "ParentRow1 Row2 Col2",
                            Col3 = "ParentRow1 Row2 Col3",
                            Col4 = "ParentRow1 Row2 Col4",
                        },
                        new ChildData()
                        {
                            Col1 = "ParentRow1 Row3 Col1",
                            Col2 = "ParentRow1 Row3 Col2",
                            Col3 = "ParentRow1 Row3 Col3",
                            Col4 = "ParentRow1 Row3 Col4",
                        },
                        new ChildData()
                        {
                            Col1 = "ParentRow1 Row4 Col1",
                            Col2 = "ParentRow1 Row4 Col2",
                            Col3 = "ParentRow1 Row4 Col3",
                            Col4 = "ParentRow1 Row4 Col4",
                        }
                    })
            });
            this._data.Add(new ParentData()
            {
                Col1 = "Row2 Col1",
                Col2 = "Row2 Col2",
                Col3 = "Row2 Col3",
                Col4 = "Row2 Col4",
                ChildData = new List<ChildData>(
                    new ChildData[] {
                        new ChildData()
                        {
                            Col1 = "ParentRow2 Row1 Col1",
                            Col2 = "ParentRow2 Row1 Col2",
                            Col3 = "ParentRow2 Row1 Col3",
                            Col4 = "ParentRow2 Row1 Col4",
                        },
                        new ChildData()
                        {
                            Col1 = "ParentRow2 Row2 Col1",
                            Col2 = "ParentRow2 Row2 Col2",
                            Col3 = "ParentRow2 Row2 Col3",
                            Col4 = "ParentRow2 Row2 Col4",
                        },
                        new ChildData()
                        {
                            Col1 = "ParentRow2 Row3 Col1",
                            Col2 = "ParentRow2 Row3 Col2",
                            Col3 = "ParentRow2 Row3 Col3",
                            Col4 = "ParentRow2 Row3 Col4",
                        },
                        new ChildData()
                        {
                            Col1 = "ParentRow2 Row4 Col1",
                            Col2 = "ParentRow2 Row4 Col2",
                            Col3 = "ParentRow2 Row4 Col3",
                            Col4 = "ParentRow2 Row4 Col4",
                        }
                    })
            });
            this._data.Add(new ParentData()
            {
                Col1 = "Row3 Col1",
                Col2 = "Row3 Col2",
                Col3 = "Row3 Col3",
                Col4 = "Row3 Col4",
                ChildData = new List<ChildData>(
                    new ChildData[] {
                        new ChildData()
                        {
                            Col1 = "ParentRow3 Row1 Col1",
                            Col2 = "ParentRow3 Row1 Col2",
                            Col3 = "ParentRow3 Row1 Col3",
                            Col4 = "ParentRow3 Row1 Col4",
                        },
                        new ChildData()
                        {
                            Col1 = "ParentRow3 Row2 Col1",
                            Col2 = "ParentRow3 Row2 Col2",
                            Col3 = "ParentRow3 Row2 Col3",
                            Col4 = "ParentRow3 Row2 Col4",
                        },
                        new ChildData()
                        {
                            Col1 = "ParentRow3 Row3 Col1",
                            Col2 = "ParentRow3 Row3 Col2",
                            Col3 = "ParentRow3 Row3 Col3",
                            Col4 = "ParentRow3 Row3 Col4",
                        },
                        new ChildData()
                        {
                            Col1 = "ParentRow3 Row4 Col1",
                            Col2 = "ParentRow3 Row4 Col2",
                            Col3 = "ParentRow3 Row4 Col3",
                            Col4 = "ParentRow3 Row4 Col4",
                        }
                    })
            });

            InitializeComponent();

            this.ParentGrid.Columns[1].SortingState = Telerik.Windows.Controls.SortingState.Descending;
        }

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            this.ParentGrid.ItemsSource = this._data;
        }
    }

    public class ParentData
    {
        public string Col1 { get; set; }
        public string Col2 { get; set; }
        public string Col3 { get; set; }
        public string Col4 { get; set; }

        private List<ChildData> _childData;
        public List<ChildData> ChildData
        {
            get
            {
                return this._childData;
            }
            set
            {
                this._childData = value;
            }
         }
    }

    public class ChildData
    {
        public string Col1 { get; set; }
        public string Col2 { get; set; }
        public string Col3 { get; set; }
        public string Col4 { get; set; }
    }
}

Thanks,
Chris

[Yavor Georgiev]

Hi Chris,

 This is by design - when you change the ItemsSource, there is no guarantee that the data will be the same and that the SortDescriptors will apply. If you want to change the data, assign an ObservableCollection to the ItemsSource and then clear it out and add new items when you wish to change the data. This way the SortDescriptors will be preserved.

Regards,
Yavor Georgiev
the Telerik team

[Chris]

Thanks, that makes sense.

[Rick Glos]

This is happening to me as well now with the update to the new controls.  Thanks for the explanation.

[Rick Glos]

In case someone else needs this, I was binding my grid to a List because I was creating the list of objects at run time.  This is because our application allows users to build a grid from a selection of hundreds of column variations.  Anyway here's the bit of code I needed to make it an ObservableCollection

Old

IList genericRunTimeList = (IList)Activator.CreateInstance(typeof(List<>).MakeGenericType(dynamicRow));

New

// Put the DynamicRowType objects in an ObserveableCollection
Type oc = typeof(ObservableCollection<>);
oc = oc.MakeGenericType(new[] { dynamicRow });
IList genericRunTimeList = (IList)Activator.CreateInstance(oc);