dotnet/wpf · error · InvalidOperationException

SR.Format(SR.CannotSortView, view)

Error message

SR.Format(SR.CannotSortView, view)

What it means

CollectionViewSource copies its SortDescriptions onto the generated view only if the view supports sorting (CanSort). If the underlying view's CanSort is false but the CollectionViewSource has one or more sort descriptions, it throws InvalidOperationException with CannotSortView because the sort request cannot be honored.

Solutions

  1. Sort the underlying collection itself before binding when the view cannot sort
  2. Ensure the generated view supports sorting (default ListCollectionView over IList does)
  3. Sort the source data (e.g. OrderBy in LINQ) and reassign Source instead of using SortDescriptions

Example fix

// before
cvs.SortDescriptions.Add(new SortDescription("Name", ListSortDirection.Ascending)); // view.CanSort == false
// after
var sorted = items.OrderBy(i => i.Name).ToList();
cvs.Source = sorted; // sort at the source
Defensive patterns

Strategy: fallback

Validate before calling

var view = (ICollectionView)typeof(CollectionViewSource).GetMethod("GetDefaultView", BindingFlags.NonPublic|BindingFlags.Instance)?.Invoke(cvs, null) ?? cvs.View; bool safe = !cvs.SortDescriptions.Any() || view?.CanSort == true;

Type guard

bool CanApplySorting(CollectionViewSource cvs) => cvs.View == null || cvs.View.CanSort || !cvs.SortDescriptions.Any();

Try / catch

try { ActivateView(); } catch (InvalidOperationException ex) when (ex.Message.Contains("CannotSortView")) { SortAtSourceInstead(); }

Prevention

When it happens

Trigger: Binding CollectionViewSource.Source to a collection whose default view does not implement sorting (e.g. some custom ICollectionView implementations) while SortDescriptions contains entries; assigning SortDescriptions before/without a sortable view type.

Common situations: Using CollectionViewSource over a custom collection with a non-sorting view; ObservableCollection views normally support sorting via ListCollectionView, but custom view factories (CollectionViewType override) may produce non-sorting views.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/a0a5c6e33c4da947. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Data/CollectionViewSource.cs:1000

                int i, n;

                // Culture
                if (Culture != null)
                {
                    view.Culture = Culture;
                }

                // Sort
                if (view.CanSort)
                {
                    view.SortDescriptions.Clear();
                    for (i=0, n=SortDescriptions.Count;  i < n;  ++i)
                    {
                        view.SortDescriptions.Add(SortDescriptions[i]);
                    }
                }
                else if (SortDescriptions.Count > 0)
                    throw new InvalidOperationException(SR.Format(SR.CannotSortView, view));

                // Filter
                Predicate<object> filter;
                if (FilterHandlersField.GetValue(this) != null)
                {
                    filter = FilterWrapper;
                }
                else
                {
                    filter = null;
                }

                if (view.CanFilter)
                {
                    view.Filter = filter;
                }
                else if (filter != null)
                    throw new InvalidOperationException(SR.Format(SR.CannotFilterView, view));

View on GitHub (pinned to 81131a70a4)