dotnet/wpf · error · InvalidEnumArgumentException

InvalidEnumArgumentException("focusNavigationDirection"…

Error message

InvalidEnumArgumentException("focusNavigationDirection", (int)focusNavigationDirection, typeof(FocusNavigationDirection))

What it means

The TraversalRequest constructor validates that focusNavigationDirection is a defined member of the FocusNavigationDirection enum, throwing InvalidEnumArgumentException otherwise. This prevents invalid navigation directions from entering the focus traversal system. It is a fail-fast guard at the public constructor boundary.

Solutions

Validate with Enum.IsDefined(typeof(FocusNavigationDirection), direction) before constructing TraversalRequest.
Use one of the named enum constants (Next, Previous, First, Last, Left, Right, Up, Down) instead of computed integers.
Clamp or normalize the computed direction into the valid range before constructing.
Catch InvalidEnumArgumentException and fall back to FocusNavigationDirection.Next.

Example fix

// before
var request = new TraversalRequest((FocusNavigationDirection)offset); // offset arbitrary
// after
if (Enum.IsDefined(typeof(FocusNavigationDirection), offset))
    var request = new TraversalRequest((FocusNavigationDirection)offset);
else
    var request = new TraversalRequest(FocusNavigationDirection.Next);

Defensive patterns

Strategy: validation

Validate before calling

bool ok = Enum.IsDefined(typeof(FocusNavigationDirection), direction);

Type guard

static bool IsValidFocusNavDirection(FocusNavigationDirection d) => Enum.IsDefined(typeof(FocusNavigationDirection), d);

Try / catch

try { var req = new TraversalRequest(direction); }
catch (InvalidEnumArgumentException) { var req = new TraversalRequest(FocusNavigationDirection.Next); }

Prevention

Use named enum constants, not computed ints.
Validate with Enum.IsDefined after any arithmetic on enum values.
Be careful casting persisted/native ints back to the enum.

When it happens

Trigger: new TraversalRequest((FocusNavigationDirection)someInt) where the int is negative or beyond the last defined enum member (FocusNavigationDirection has values 0-6, so anything outside that range).

Common situations: Computing a navigation direction arithmetically from a key press or index; deserializing persisted UI state with a stale int; interop code passing unvalidated native values.

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/95365fe094a02c17. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/WindowsBase/System/Windows/TraversalRequest.cs:27

            if (focusNavigationDirection != FocusNavigationDirection.Next &&
                 focusNavigationDirection != FocusNavigationDirection.Previous &&
                 focusNavigationDirection != FocusNavigationDirection.First &&
                 focusNavigationDirection != FocusNavigationDirection.Last &&
                 focusNavigationDirection != FocusNavigationDirection.Left &&
                 focusNavigationDirection != FocusNavigationDirection.Right &&
                 focusNavigationDirection != FocusNavigationDirection.Up &&
                 focusNavigationDirection != FocusNavigationDirection.Down)
            {
                throw new System.ComponentModel.InvalidEnumArgumentException("focusNavigationDirection", (int)focusNavigationDirection, typeof(FocusNavigationDirection));
            }

            _focusNavigationDirection = focusNavigationDirection;

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