dotnet/wpf · error · InvalidEnumArgumentException

InvalidEnumArgumentException("value", (int)value…

Error message

InvalidEnumArgumentException("value", (int)value, typeof(ShutdownMode))

What it means

The Application.ShutdownMode property setter verifies the value is a defined ShutdownMode enum member (OnLastWindowClose, OnMainWindowClose, OnExplicitShutdown). Passing an out-of-range integer cast to the enum throws InvalidEnumArgumentException. This prevents the app from entering an undefined shutdown behavior.

Solutions

Validate with Enum.IsDefined(typeof(ShutdownMode), value) before assigning
Only assign literal ShutdownMode enum members, not raw ints
Sanitize config-driven integers with a fallback to ShutdownMode.OnLastWindowClose
Call from the UI thread — the setter also requires thread affinity (VerifyAccess)

Example fix

// before
app.ShutdownMode = (ShutdownMode)configValue;
// after
var mode = Enum.IsDefined(typeof(ShutdownMode), configValue) ? (ShutdownMode)configValue : ShutdownMode.OnLastWindowClose;
app.ShutdownMode = mode;

Defensive patterns

Strategy: validation

Validate before calling

bool isValidMode(int v) => Enum.IsDefined(typeof(ShutdownMode), v);

Type guard

bool TryGetShutdownMode(int raw, out ShutdownMode mode) { if (Enum.IsDefined(typeof(ShutdownMode), raw)) { mode = (ShutdownMode)raw; return true; } mode = ShutdownMode.OnLastWindowClose; return false; }

Try / catch

try { app.ShutdownMode = mode; } catch (InvalidEnumArgumentException ex) { app.ShutdownMode = ShutdownMode.OnLastWindowClose; }

Prevention

Validate config integers with Enum.IsDefined
Assign only named enum members
Set on the UI thread
Sanitize persisted enum values on read

When it happens

Trigger: Assigning app.ShutdownMode = (ShutdownMode)someInt where someInt is not 0-2, e.g. values loaded from config, parsed from user input, or arithmetic results, without validating the enum range.

Common situations: Persisting ShutdownMode to config files and reading back stale/invalid numbers; reflection-based property assignment; enum values changed between library versions.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

AI-assisted analysis of dotnet/wpf@81131a70a4 (2026-09-14). Data as JSON: /api/errors/ccac477bce8d381f. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Application.cs:836

        ///                             been set - this mode is equivalent to OnExplicitOnly.
        ///
        ///         OnExplicitShutdown- this mode will shutdown the application only when an
        ///                             explicit call to OnShutdown() has been made.
        /// </summary>
        public ShutdownMode ShutdownMode
        {
            get
            {
                VerifyAccess();
                return _shutdownMode;
            }

            set
            {
                VerifyAccess();
                if ( !IsValidShutdownMode(value) )
                {
                    throw new InvalidEnumArgumentException("value", (int)value, typeof(ShutdownMode));
                }
                if (IsShuttingDown || _appIsShutdown)
                {
                    throw new InvalidOperationException(SR.ShutdownModeWhenAppShutdown);
                }

                _shutdownMode = value;
            }
        }

        /// <summary>
        ///     Current locally defined Resources
        /// </summary>
        [Ambient]
        public ResourceDictionary Resources
        {
            //Don't use  VerifyAccess() here since Resources can be set from any thread.
            //We synchronize access using _globalLock

View on GitHub (pinned to 81131a70a4)