dotnet/wpf · error · InvalidEnumArgumentException

InvalidEnumArgumentException(argumentName, direction…

Error message

InvalidEnumArgumentException(argumentName, direction, LogicalDirection)

What it means

ValidationHelper.VerifyDirection rejects any LogicalDirection value other than Forward or Backward, throwing InvalidEnumArgumentException with the caller-supplied argument name. LogicalDirection is a two-value enum; anything else (e.g. a cast invalid int) is an invalid enum argument.

Solutions

Pass only LogicalDirection.Forward or LogicalDirection.Backward.
Validate/parse the source int with Enum.IsDefined before casting.
Clamp or normalize persisted values at load time.

Example fix

// before
var dir = (LogicalDirection)userValue; // userValue = 5
// after
var dir = Enum.IsDefined(typeof(LogicalDirection), userValue) ? (LogicalDirection)userValue : LogicalDirection.Forward;

Defensive patterns

Strategy: validation

Validate before calling

if (!Enum.IsDefined(typeof(LogicalDirection), value)) throw new InvalidEnumArgumentException(nameof(value), value, typeof(LogicalDirection));

Type guard

bool IsValidLogicalDirection(object v) => v is LogicalDirection d && (d == LogicalDirection.Forward || d == LogicalDirection.Backward);

Try / catch

try { ... } catch (InvalidEnumArgumentException ex) { /* repair or default the direction */ }

Prevention

Never cast raw ints to LogicalDirection without Enum.IsDefined
Validate persisted enum values at deserialization time

When it happens

Trigger: Passing a LogicalDirection value obtained by casting an out-of-range int (e.g. (LogicalDirection)2) to any API that routes through VerifyDirection.

Common situations: Deserializing enum values from config or persisted data where the raw int is unvalidated; arithmetic on enum 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/2f34b864b9250c8c. Report an issue: GitHub.

Appendix: source

Thrown at src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Documents/ValidationHelper.cs:73

            ArgumentNullException.ThrowIfNull(startPosition);
            ArgumentNullException.ThrowIfNull(endPosition);
            if (startPosition.TextContainer != endPosition.TextContainer)
            {
                throw new ArgumentException(SR.Format(SR.InDifferentTextContainers, "startPosition", "endPosition"));
            }
            if (startPosition.CompareTo(endPosition) > 0)
            {
                throw new ArgumentException(SR.Format(SR.BadTextPositionOrder, "startPosition", "endPosition"));
            }
        }

        // Throws an ArgumentException if direction is not a valid enum.
        internal static void VerifyDirection(LogicalDirection direction, string argumentName)
        {
            if (direction != LogicalDirection.Forward &&
                direction != LogicalDirection.Backward)
            {
                throw new InvalidEnumArgumentException(argumentName, (int)direction, typeof(LogicalDirection));
            }
        }

        // Throws an ArgumentException if edge is not a valid enum.
        internal static void VerifyElementEdge(ElementEdge edge, string param)
        {
            if (edge != ElementEdge.BeforeStart &&
                edge != ElementEdge.AfterStart  &&
                edge != ElementEdge.BeforeEnd   &&
                edge != ElementEdge.AfterEnd)
            {
                throw new InvalidEnumArgumentException(param, (int)edge, typeof(ElementEdge));
            }
        }

        // ...............................................................
        //
        // TextSchema Validation

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