This post will show you how to override the built-in sorting functionality and sort the DataGrid data using the SortDescription class. The data content is sorted when a user clicks a column header.

1. The following example defines a DataGrid with six columns that bind to the Name, Date, Product, Quantity, UnitPrice and SalesAmount properties of the EmployeeSaleRecord class.

     <viblendDataGrid:DataGrid AutoGenerateColumns="True" Height="200" VerticalAlignment="Center" Name="dataGrid" Width="350">
            <viblendDataGrid:DataGrid.BoundFields>               
                <viblendDataGrid:BoundField Text="Name" DataField="Name" Width="160"  CellStyle="{StaticResource textCentered}"/>
                <viblendDataGrid:BoundField Text="Date" DataField="Date" Width="140" />
                <viblendDataGrid:BoundField Text="Product" DataField="Product" Width="140"  CellStyle="{StaticResource textCentered}"/>
                <viblendDataGrid:BoundField Text="Quantity" DataField="Quantity" Width="90"  CellStyle="{StaticResource textCentered}"/>
                <viblendDataGrid:BoundField Text="Unit Price" DataField="UnitPrice" Width="74"/>
                <viblendDataGrid:BoundField Text="Sales Amount" DataField="SalesAmount" Width="88"/>
            </viblendDataGrid:DataGrid.BoundFields>
        </viblendDataGrid:DataGrid>

2. Create column header templates with up and down arrow elements that will be displayed when the grid data is sorted.

    <UserControl.Resources>
        <Style x:Name="textCentered" TargetType="viblendDataGrid:GridCellElement">
            <Setter Property="HorizontalContentAlignment" Value="Center" />
            <Setter Property="VerticalContentAlignment" Value="Center" />
        </Style>

        <DataTemplate x:Key="SortAscendingTemplate">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*"></ColumnDefinition>
                    <ColumnDefinition Width="Auto"></ColumnDefinition>
                </Grid.ColumnDefinitions>
                <TextBlock Text="{Binding}"></TextBlock>
                <Path Grid.Column="1" x:Name="sortAscElement" Height="5" Width="9" Stretch="Fill" Stroke="#FFFFFFFF" Data="M4.5,5 L0,0 L9,0 z" RenderTransformOrigin="0.0,0.0">
                    <Path.Fill>
                        <LinearGradientBrush EndPoint="-0.237,0.525" StartPoint="0.679,0.525">
                            <GradientStop Color="#55FFFFFF"/>
                            <GradientStop Color="#55FFFFFF" Offset="0.991"/>
                        </LinearGradientBrush>
                    </Path.Fill>
                </Path>
            </Grid>
        </DataTemplate>
        <DataTemplate x:Key="SortDescendingTemplate">
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="*"></ColumnDefinition>
                    <ColumnDefinition Width="Auto"></ColumnDefinition>
                </Grid.ColumnDefinitions>
                <TextBlock Text="{Binding}"></TextBlock>
                <Path Grid.Column="1" x:Name="sortDescElement" Height="5" Width="9" Stretch="Fill" Stroke="#FFFFFFFF" Data="M4.5,0 L9,5 L0,5 z" RenderTransformOrigin="0.0,0.0" >
                    <Path.Fill>
                        <LinearGradientBrush EndPoint="-0.237,0.525" StartPoint="0.679,0.525">
                            <GradientStop Color="#55FFFFFF"/>
                            <GradientStop Color="#55FFFFFF" Offset="0.991"/>
                        </LinearGradientBrush>
                    </Path.Fill>
                </Path>
            </Grid>
        </DataTemplate>
    </UserControl.Resources>

3. Create  CollectionViewSource, HierarchyItem and bool? fields in the code behind.
4. Bind the DataGrid to a List of EmployeeSaleRecord objects. Set the selection mode to row selection and hide the row headers.

    C#

    // Bind DataGrid
    dataGrid.ItemsSource = listSaleRecord;
    dataGrid.SelectionMode = DataGrid.SELECTION_MODE.FULL_ROW_SELECT;
    dataGrid.RowsHierarchy.Visible = false; 

     VB .NET
    ' Bind DataGrid
    dataGrid.ItemsSource = listSaleRecord
    dataGrid.SelectionMode = DataGrid.SELECTION_MODE.FULL_ROW_SELECT
    dataGrid.RowsHierarchy.Visible = False

5. To sort the data according to the contents of a column, the example defines an event handler to handle the HierarchyItemMouseClick event that occurs when you press the column header.  In the event handler, toggle the sorting order and set the DataTemplate property of the HierarchyItem object depending on the sort order. Call the Sort method and  set the DataGrid.ItemsSource property to point to the view. Doing this, the DataGrid will be refreshed and sorted.
      

       C#
       // Subscribe to HierarchyItemMouseClick event.
      dataGrid.HierarchyItemMouseClick += new DataGrid.HierarchyItemMouseButtonEventHandler(dataGrid_HierarchyItemMouseClick);

      void dataGrid_HierarchyItemMouseClick(object sender, HierarchyItemMouseButtonEventArgs args)
        {
            if (clickedItem != null && !args.HierarchyItem.BoundField.DataField.Equals(clickedItem.BoundField.DataField))
            {
                clickedItem.BoundField.DataTemplate = null;
                ascending = null;
            }

            clickedItem = args.HierarchyItem;
            clickedItem.BoundField.DataContext = clickedItem.BoundField.DataField;

            // Load the column's DataTemplate
            if (ascending == null)
            {
                ascending = true;
                clickedItem.BoundField.DataTemplate = this.Resources["SortDescendingTemplate"] as DataTemplate;
            }
            else if (ascending.HasValue && !ascending.Value)
            {
                ascending = null;
                clickedItem.BoundField.DataTemplate = null;
            }
            else if (ascending.HasValue && ascending.Value)
            {
                ascending = false;
                clickedItem.BoundField.DataTemplate = this.Resources["SortAscendingTemplate"] as DataTemplate;
            }

            if (ascending == null)
            {
                dataGrid.ItemsSource = listSaleRecord;
            }
            else
            {
                SortDescription sortDescription = new SortDescription(args.HierarchyItem.BoundField.DataField, ascending == true ? ListSortDirection.Ascending : ListSortDirection.Descending);
                ICollectionView view = Sort(sortDescription, args.HierarchyItem.BoundField.DataField, this.listSaleRecord);
                dataGrid.ItemsSource = view;
            }
        }

      VB .NET

      ' Subscribe to HierarchyItemMouseClick event.
      Private dataGrid.HierarchyItemMouseClick += New DataGrid.HierarchyItemMouseButtonEventHandler(AddressOf dataGrid_HierarchyItemMouseClick)

      Private Sub dataGrid_HierarchyItemMouseClick(ByVal sender As Object, ByVal args As HierarchyItemMouseButtonEventArgs)
            If clickedItem IsNot Nothing AndAlso (Not args.HierarchyItem.BoundField.DataField.Equals(clickedItem.BoundField.DataField)) Then
                clickedItem.BoundField.DataTemplate = Nothing
                ascending = Nothing
            End If

            clickedItem = args.HierarchyItem
            clickedItem.BoundField.DataContext = clickedItem.BoundField.DataField

            ' Load the column's DataTemplate
            If ascending Is Nothing Then
                ascending = True
                clickedItem.BoundField.DataTemplate = TryCast(Me.Resources("SortDescendingTemplate"), DataTemplate)
            ElseIf ascending.HasValue AndAlso (Not ascending.Value) Then
                ascending = Nothing
                clickedItem.BoundField.DataTemplate = Nothing
            ElseIf ascending.HasValue AndAlso ascending.Value Then
                ascending = False
                clickedItem.BoundField.DataTemplate = TryCast(Me.Resources("SortAscendingTemplate"), DataTemplate)
            End If

            If ascending Is Nothing Then
                dataGrid.ItemsSource = listSaleRecord
            Else
                Dim sortDescription As New SortDescription(args.HierarchyItem.BoundField.DataField,If(ascending = True, ListSortDirection.Ascending, ListSortDirection.Descending))
                Dim view As ICollectionView = Sort(sortDescription, args.HierarchyItem.BoundField.DataField, Me.listSaleRecord)
                dataGrid.ItemsSource = view
            End If
      End Sub

6. Implement the Sort method. Add the SortDescription instance to the CollectionViewSource and return the view which will be used as DataGrid items source.

      C#

       public virtual ICollectionView Sort(SortDescription sortDescription, string columnName, System.Collections.IEnumerable itemsSource)
        {
            if (sortDescription == null)
                return null;

            string displayMember = columnName;

            if (String.IsNullOrEmpty(displayMember))
            {
                displayMember = "";
            }

            viewSource.SortDescriptions.Clear();
            if (itemsSource != null)
            {
                if (itemsSource as ICollectionView != null)
                {
                    viewSource.Source = (itemsSource as ICollectionView).SourceCollection;
                }
                else
                {
                    viewSource.Source = itemsSource;
                }

                viewSource.SortDescriptions.Add(sortDescription);
                return viewSource.View;
            }

            return null;
        }

     VB .NET

     Public Overridable Function Sort(ByVal sortDescription As SortDescription, ByVal columnName As String, ByVal itemsSource As System.Collections.IEnumerable) As ICollectionView
            If sortDescription Is Nothing Then
                Return Nothing
            End If

            Dim displayMember As String = columnName

            If String.IsNullOrEmpty(displayMember) Then
                displayMember = ""
            End If

            viewSource.SortDescriptions.Clear()
            If itemsSource IsNot Nothing Then
                If TryCast(itemsSource, ICollectionView) IsNot Nothing Then
                    viewSource.Source = (TryCast(itemsSource, ICollectionView)).SourceCollection
                Else
                    viewSource.Source = itemsSource
                End If

                viewSource.SortDescriptions.Add(sortDescription)
                Return viewSource.View
            End If

            Return Nothing
     End Function

Download demo project: DataGridCustomSortingDemo.zip