dotnet/efcore · error · InvalidOperationException

Could not find symbol for typeof() expression: {typeOf}

Error message

Could not find symbol for typeof() expression: {typeOf}

What it means

VisitTypeOfExpression throws InvalidOperationException when typeof(T) inside a precompiled query cannot be resolved to an ITypeSymbol by Roslyn. The translator needs the type symbol to map typeof to a Constant expression over System.Type.

Source

Thrown at src/EFCore.Design/Query/Internal/CSharpToLinqTranslator.cs:1011

    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
    ///     any release. You should only use it directly in your code with extreme caution and knowing that
    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
    /// </summary>
    public override Expression VisitSimpleLambdaExpression(SimpleLambdaExpressionSyntax lambda)
        => VisitLambdaExpression(lambda);

    /// <summary>
    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
    ///     any release. You should only use it directly in your code with extreme caution and knowing that
    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
    /// </summary>
    public override Expression VisitTypeOfExpression(TypeOfExpressionSyntax typeOf)
    {
        if (_semanticModel.GetSymbolInfo(typeOf.Type).Symbol is not ITypeSymbol typeSymbol)
        {
            throw new InvalidOperationException(
                "Could not find symbol for typeof() expression: " + typeOf);
        }

        var type = ResolveType(typeSymbol);
        return Constant(type, typeof(Type));
    }

    /// <summary>
    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
    ///     any release. You should only use it directly in your code with extreme caution and knowing that
    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
    /// </summary>
    public override Expression DefaultVisit(SyntaxNode node)
        => throw new NotSupportedException($"Unsupported syntax node of type '{node.GetType()}': {node}");

    private Expression VisitLambdaExpression(AnonymousFunctionExpressionSyntax lambda, Type? expectedType = null)
    {

View on GitHub (pinned to dbf9771522)

Solutions

Reference the assembly that defines the type used in typeof()
Avoid typeof() of unresolved types in precompiled queries
Capture the needed Type in a local variable outside the query and reference that

Example fix

// before (ExternalFlag in unreferenced assembly)
var q = ctx.Items.Where(i => i.Kind == typeof(ExternalFlag));
// after (referenced type)
var q = ctx.Items.Where(i => i.Kind == typeof(KnownFlag));

Defensive patterns

Strategy: validation

Validate before calling

// Ensure the type used in typeof() is referenced by the precompilation.
var t = typeof(ExternalFlag);
// If the type is in another assembly, add a MetadataReference for that assembly.

Prevention

Reference the assembly of any type used in typeof() within a precompiled query
Avoid typeof() of error/unresolved types
Capture the needed Type in a local computed outside the query

When it happens

Trigger: typeof(SomeType) where SomeType is in an unreferenced assembly, is an error type, or otherwise fails to bind in the precompilation.

Common situations: typeof() of a type defined in an assembly not referenced by the precompiled-query compilation; typeof of a type whose source has compile errors.

Related errors

AI-assisted analysis of dotnet/efcore@dbf9771522 (2026-08-06). Data as JSON: /api/errors/2e5909bc7aa91d67. Report an issue: GitHub.