Question

I have a silverlight datagrid which is bound to a PagedCollectionView displaying a collection of RowViewModels.

Each RowVM has a collection of CellViewModels, and the datagrid columns are templatecolumns and are generated dynamically with their content bound to Cell[0].Content, Cell[1].Content, etc. This is because the rowviewmodels are returned from a service, and can contain any number of columns and different types of content.

This works just fine, but I’ve run into problems when enabling sorting of columns in the datagrid. It seems the SortMemberPath property on DataGridColumns (which in the end becomes a SortDescription.PropertyName) won’t work with an expression containing an index, like “Cells[1].Content”.

Does anyone know a way around this?

Answer 1

Answering my own question here.

I solved this by setting SortMemberPath on my generated columns to their index number in the RowVM.Cells collection, and added a SortOnMe property to my RowVMs.

When the user sorts the datagrid, it will add a SortDescription containing the index number (taken from the SortMemberPath) to the PagedCollectionView. I monitor this by listening to the propertychanged event on the PagedCollectionView with the method below. It adds a new SortDescription telling the PagedCollectionView to sort on “SortOnMe”, and copies the data to sort on from the cell in question to row.SortOnMe.

private bool _currentlySorting;
private void PagedCollectionView_PropertyChanged(object sender, PropertyChangedEventArgs e)
{
    var pcv = (PagedCollectionView)sender;
    int columnIndex = 0;
    if (!_currentlySorting && e.PropertyName == "SortDescriptions" && pcv.SortDescriptions.Count == 1 && int.TryParse(pcv.SortDescriptions[0].PropertyName, out columnIndex)) {
        _currentlySorting = true; 
        pcv.SortDescriptions.Add(new SortDescription("SortOnMe", pcv.SortDescriptions(0).Direction));
        foreach (RowViewModel row in pcv.SourceCollection) {
            row.SortOnMe = row.Cells(columnIndex).Content;
        }
        _currentlySorting = false;
    }
}

It’s a pretty ugly solution, to be honest. But it works, and I’ve spent too much time bashing my head against this wall now.

Since PagedCollectionView is a sealed class (why?!), the only other way I could think of doing this would be to create my own PagedCollectionView and handle sorting there.