dotnet/wpf · error · InvalidOperationException

SR.ShowNonActivatedAndMaximized

Error message

SR.ShowNonActivatedAndMaximized

What it means

Window.Show throws InvalidOperationException when a window is set to WindowState.Maximized with ShowActivated=false and the window is not an internal trusted sub-window. WPF does not support showing a maximized window without activating it, because the Windows platform cannot reliably display a non-activated maximized top-level window. The check is skipped for RBW (restricted browser windows) which set Visibility during launch.

Solutions

  1. Remove ShowActivated="False" so the window activates normally when maximized.
  2. Keep ShowActivated=false but set WindowState to Normal; maximize the window after it is shown (e.g. in the Loaded/SourceInitialized handler) via WindowState = WindowState.Maximized.
  3. Maximize via Win32 ShowWindow with SW_SHOWMAXIMIZED/SW_SHOWNOACTIVATE after SourceInitialized if you truly need a no-activate maximized window.
  4. If this is not your window's intent, check that a style/template or base window class is not accidentally setting ShowActivated=false.

Example fix

// before
var win = new MainWindow { WindowState = WindowState.Maximized, ShowActivated = false };
win.Show();
// after
var win = new MainWindow { WindowState = WindowState.Normal, ShowActivated = false };
win.Show();
win.Loaded += (s, e) => win.WindowState = WindowState.Maximized;
Defensive patterns

Strategy: validation

Validate before calling

if (win.WindowState == WindowState.Maximized && !win.ShowActivated)
    throw new InvalidOperationException("Maximized windows must have ShowActivated=true in WPF.");

Try / catch

try { win.Show(); }
catch (InvalidOperationException) { win.ShowActivated = true; win.Show(); }

Prevention

When it happens

Trigger: Calling Show() (or ShowDialog reaching the show path) on a Window where WindowState == WindowState.Maximized and ShowActivated == false, and the window was not created internally as a trusted sub-window (_inTrustedSubWindow is false).

Common situations: Developers wanting a 'background' maximized window set ShowActivated="False" in XAML together with WindowState="Maximized", or set these properties in code before calling Show; common in kiosk/dashboard apps that try to avoid focus stealing.

Understand the failure class

Background: "Invalid state transition" errors: "status must be X, actually Y", "already rejected/charging/uninstalled", "cannot ... while running" — what they mean when a library rejects your call — this error's family across 31 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/915b86cbe6464cc1. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Window.cs:6943

            }
        }

        private void VerifyConsistencyWithAllowsTransparency(WindowStyle style)
        {
            if (AllowsTransparency && style != WindowStyle.None)
            {
                throw new InvalidOperationException(SR.MustUseWindowStyleNone);
            }
        }

        private void VerifyConsistencyWithShowActivated()
        {
            //
            // We don't support to show a maximized non-activated window.
            // Don't check this consistency in a RBW (would break because Visibility is set when launching the RBW).
            //
            if (!_inTrustedSubWindow && WindowState == WindowState.Maximized && !ShowActivated)
                throw new InvalidOperationException(SR.ShowNonActivatedAndMaximized);
        }

        private static bool IsValidSizeToContent(SizeToContent value)
        {
            return value == SizeToContent.Manual ||
                   value == SizeToContent.Width ||
                   value == SizeToContent.Height ||
                   value == SizeToContent.WidthAndHeight;
        }

        private static bool IsValidResizeMode(ResizeMode value)
        {
            return value == ResizeMode.NoResize
                || value == ResizeMode.CanMinimize
                || value == ResizeMode.CanResize
                || value == ResizeMode.CanResizeWithGrip;
        }

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