Datagrid Multiple Column Sorting

Question

My datagrid is setup like this:

• ItemsSource bound to ObservableCollection
• Handling Sorting event
  • e.Handled = true;
  • Clear observable collection
  • Query database with sorting logic
  • Foreach result add to observable collection

This works great but I want to enable multiple column sorting. It's my understanding that holding shift while clicking column headings is the way the end user does this. But in the sorting event, I don't know how to get a hold of the sort descriptions.

Here's my code for single column server side sorting, which works fine:

public class DataGrid : System.Windows.Controls.DataGrid
{
    public event EventHandler<SortExpressionConstructedEventArgs> SortExpressionConstructed;

    public void OnSortExpressionConstructed(SortExpressionConstructedEventArgs e)
    {
        EventHandler<SortExpressionConstructedEventArgs> handler = SortExpressionConstructed;
        if (handler != null) handler(this, e);
    }


    public DataGrid()
    {
        Sorting += DataGridSorting;
    }

    void DataGridSorting(object sender, System.Windows.Controls.DataGridSortingEventArgs e)
    {
        e.Handled = true;
        e.Column.SortDirection = e.Column.SortDirection != ListSortDirection.Ascending
                                     ? ListSortDirection.Ascending
                                     : ListSortDirection.Descending;

        var sd = new SortDescription(e.Column.SortMemberPath, e.Column.SortDirection.Value);
        OnSortExpressionConstructed(new SortExpressionConstructedEventArgs(sd));
    }
}

public class SortExpressionConstructedEventArgs : EventArgs
{
    public SortExpressionConstructedEventArgs(SortDescription sortDescription)
    {
        SortDescription = sortDescription;
    }

    public SortDescription SortDescription { get; private set; }

    // event handler can use this to sort the query
    public IOrderedQueryable<T> Order<T>(IQueryable<T> queryable)
    {
        switch (SortDescription.Direction)
        {
            case ListSortDirection.Ascending:
                return enumerable.OrderBy(SortDescription.PropertyName);

            case ListSortDirection.Descending:
                return enumerable.OrderByDescending(SortDescription.PropertyName);

            default:
                throw new ArgumentOutOfRangeException();
        }
    }
}

Answer 1

My solution was to manually track the sorted columns in the derived DataGrid class, which is working well.

https://github.com/ronnieoverby/RonnieOverbyGrabBag/blob/master/DataGrid.cs

Answer 2

My method is work for me. Just try this code.

if (dgEvents.ItemsSource == null)
    dgEvents.ItemsSource = events.Entries;

CollectionViewSource.GetDefaultView(dgEvents.ItemsSource).Refresh();

dgEvents.Items.SortDescriptions.Clear();

dgEvents.Items.SortDescriptions.Add(new SortDescription(dgEvents.Columns[0].SortMemberPath, ListSortDirection.Descending));


foreach (var col in dgEvents.Columns)
{
    col.SortDirection = null;
}

dgEvents.Columns[0].SortDirection = ListSortDirection.Descending;

dgEvents.Items.Refresh();