dotnet/wpf · error · InvalidOperationException

SR.Format(SR.CannotCallRunMultipleTimes…

Error message

SR.Format(SR.CannotCallRunMultipleTimes, this.GetType().FullName)

What it means

Application.Run can only execute the application's message loop once. When Run (or Run(Window)) is called after the application has already shut down (_appIsShutdown true), WPF throws InvalidOperationException naming the application type. A single Application instance manages exactly one lifetime.

Solutions

Call Run exactly once per Application instance, at the entry point (Main/App.g.cs)
To restart, create a new Application instance (in a fresh process if needed) and Run that
Check Application.Current == null or _appIsShutdown semantics — track whether Run already returned before calling again
In tests, build a fresh Application (or avoid Run entirely) per fixture

Example fix

// before
app.Run();
// ... later, same instance
app.Run(); // throws
// after
app.Run();
// restart with a new instance
var app2 = new MyApp();
app2.Run();

Defensive patterns

Strategy: type-guard

Validate before calling

bool canRun() => Application.Current == null || !Application.Current.Dispatcher.HasShutdownStarted;

Type guard

bool RunAlreadyCompleted(MyApp app) => app.Dispatcher.HasShutdownFinished;

Try / catch

try { app.Run(); } catch (InvalidOperationException) { /* create a new Application instance to restart */ }

Prevention

Call Run once from the app entry point
Create a new Application to restart
Never call Run from event handlers
In tests, instantiate a fresh Application per case

When it happens

Trigger: Calling app.Run() a second time after Shutdown() completed; restarting the loop from Exit handlers; re-invoking Run after Run(Window) returned because the window closed; test code reusing an Application instance across test cases.

Common situations: Attempts to 'restart' an app without creating a new Application; repeated Run calls in loops; unit-test fixtures instantiating one Application but calling Run per test.

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/0afd20ab4dfd17b8. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Application.cs:1680

            EventTrace.EasyTraceEvent(EventTrace.Keyword.KeywordGeneral | EventTrace.Keyword.KeywordPerf, EventTrace.Event.WClientAppRun);

            //
            // (Can't create app and do run/shutdown followed
            // by run/shutdown)
            //
            // Devs could write the following code
            //
            // Application app = new Application();
            // app.Run();
            // app.Run();
            //
            // In this case, we should throw an exception when Run is called for the second time.
            // When app is shutdown, _appIsShutdown is set to true.  If it is true here, then we
            // throw an exception
            if (_appIsShutdown)
            {
                throw new InvalidOperationException(SR.Format(SR.CannotCallRunMultipleTimes, this.GetType().FullName));
            }

            if (window != null)
            {
                if (!window.CheckAccess())
                {
                    throw new ArgumentException(SR.Format(SR.WindowPassedShouldBeOnApplicationThread, window.GetType().FullName, this.GetType().FullName));
                }

                if (!WindowsInternal.HasItem(window))
                {
                    WindowsInternal.Add(window);
                }

                if (MainWindow == null)
                {
                    MainWindow = window;
                }

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