dotnet/wpf · error · InvalidOperationException

throw new…

Error message

throw new InvalidOperationException(SR.OperationCannotBePerformed);

What it means

RemoveFromSelection throws InvalidOperationException(SR.OperationCannotBePerformed) when the grid item's cell contains no date (GetDateTime() == DateTime.MinValue), so there is nothing selectable to remove from the selection.

Solutions

1. Check the item has a date (e.g. via its name/value) before calling RemoveFromSelection
2. Skip empty cells in automation loops
3. Catch InvalidOperationException and continue with the next cell

Example fix

// before
foreach (var cell in cells) cell.RemoveFromSelection();
// after
foreach (var cell in cells)
    if (DateTime.TryParse(cell.Name, out _)) cell.RemoveFromSelection();

if (!DateTime.TryParse(cell.Current.Name, out _)) return; // empty cell

bool HasSelectableDate(AutomationElement c) => DateTime.TryParse(c.Current.Name, out _);

try { cell.RemoveFromSelection(); } catch (InvalidOperationException) { /* blank cell, ignore */ }

When it happens

Trigger: Calling RemoveFromSelection on a blank filler cell of the MonthCalendar grid (cell before/after the displayed week dates).

Common situations: Iterating all grid cells and removing each from selection without checking that the cell holds a date.

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

• SR.Calendar_OnSelectedDateChanged_InvalidOperation
• SR.VirtualizedElement
• E_ACCESSDENIED
• E_INVALIDARG
• E_OUTOFMEMORY

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/8caf380ab6496777. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/UIAutomation/UIAutomationClientSideProviders/MS/Internal/UnsupportedAutomationProxies/WindowsCalendar.cs:3757

                    {
                        return;
                    }

                    if (!WindowsCalendar.IsMultiSelect (_hwnd))
                    {
                        throw new InvalidOperationException(SR.DoesNotSupportMultipleSelection);
                    }

                    DateTime [] dateSelection =
                        WindowsCalendar.CreateDateTimeFromSystemTime (
                            WindowsCalendar.GetRawValue (
                                _hwnd, WindowsCalendar.CalendarData.Selection));

                    DateTime itemDateTime = GetDateTime();

                    if (itemDateTime == DateTime.MinValue)
                    {
                        throw new InvalidOperationException(SR.OperationCannotBePerformed);
                    }

                    TimeSpan ts = itemDateTime - dateSelection[0];

                    //If both date times in the dateSelection are same, then only one date is
                    //currently selected. We cannot remove the selection if its only the selected one.
                    if ((dateSelection[1] - dateSelection[0]).Days == 0)
                    {
                        throw new InvalidOperationException(SR.OperationCannotBePerformed);
                    }
                    else if (ts.Days == 0)
                    {
                        dateSelection [0] = dateSelection [0].AddDays (1);
                    }
                    else if ((ts = (dateSelection[1] - itemDateTime)).Days == 0)
                    {
                        dateSelection [1] = dateSelection [1].AddDays (-1);
                    }

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