{"record":{"id":"ff9bac415fa12158","repo":"dotnet/efcore","slug":"the-entity-type-entitytype-is-mapped-to-the-d-ff9bac","errorCode":null,"errorMessage":"The entity type '{entityType}' is mapped to the 'DbFunction' named '{functionName}' with parameters {parameters}. Ensure that the mapped function doesn't have any parameters.","messagePattern":"The entity type '(.+?)' is mapped to the 'DbFunction' named '(.+?)' with parameters (.+?)\\. Ensure that the mapped function doesn't have any parameters\\.","errorType":"exception","errorClass":"InvalidOperationException","httpStatus":null,"severity":"error","filePath":"src/EFCore.Relational/Infrastructure/RelationalModelValidator.cs","lineNumber":462,"sourceCode":"        if (mappedFunction.IsScalar\n            || mappedFunction.ReturnType.GetGenericArguments()[0] != entityType.ClrType)\n        {\n            throw new InvalidOperationException(\n                RelationalStrings.InvalidMappedFunctionUnmatchedReturn(\n                    entityType.DisplayName(),\n                    mappedFunctionName,\n                    mappedFunction.ReturnType.ShortDisplayName(),\n                    entityType.ClrType.ShortDisplayName()));\n        }\n\n        if (mappedFunction.Parameters.Count > 0)\n        {\n            var parameters = \"{\"\n                + string.Join(\n                    \", \",\n                    mappedFunction.Parameters.Select(p => \"'\" + p.Name + \"'\"))\n                + \"}\";\n            throw new InvalidOperationException(\n                RelationalStrings.InvalidMappedFunctionWithParameters(\n                    entityType.DisplayName(), mappedFunctionName, parameters));\n        }\n    }\n\n    /// <summary>\n    ///     Validates the stored procedures for an entity type.\n    /// </summary>\n    /// <param name=\"entityType\">The entity type to validate.</param>\n    /// <param name=\"logger\">The logger to use.</param>\n    protected virtual void ValidateStoredProcedures(\n        IEntityType entityType,\n        IDiagnosticsLogger<DbLoggerCategory.Model.Validation> logger)\n    {\n        var mappingStrategy = entityType.GetMappingStrategy() ?? RelationalAnnotationNames.TphMappingStrategy;\n\n        var sprocCount = 0;\n        var deleteStoredProcedure = entityType.GetDeleteStoredProcedure();","sourceCodeStart":444,"sourceCodeEnd":480,"githubUrl":"https://github.com/dotnet/efcore/blob/dbf9771522148d61a2467854921bd5dc6f6e6916/src/EFCore.Relational/Infrastructure/RelationalModelValidator.cs#L444-L480","documentation":"Thrown when a DbFunction used for entity mapping has one or more parameters. A function-backed entity type must map to a parameterless DbFunction because it represents the full rowset; parameterized functions are query operators, not mapping targets. The validator rejects mappedFunction.Parameters.Count > 0.","triggerScenarios":"Mapping an entity to HasDbFunction(x => x.GetBlogs(category)) where the method takes arguments; a DbFunction with optional parameters reused as a mapping target.","commonSituations":"Wanting a parameterized query but accidentally using ToFunction for mapping; converting a filtered query method into a mapping source.","solutions":["Remove all parameters from the mapped DbFunction method.","Keep the parameterized method as a regular queryable DbFunction (HasDbFunction) but do not call ToFunction on the entity.","Provide a separate parameterless DbFunction specifically for the entity mapping."],"exampleFix":"// before\npublic IQueryable<Blog> GetBlogs(int categoryId) => ...;\nmodelBuilder.Entity<Blog>().ToFunction(\"GetBlogs\");\n\n// after\npublic IQueryable<Blog> GetBlogs() => FromSqlInterpolated($\"SELECT * FROM vw_Blogs\");\nmodelBuilder.Entity<Blog>().ToFunction(\"GetBlogs\");","handlingStrategy":"validation","validationCode":"foreach (var et in modelBuilder.Model.GetEntityTypes())\n{\n    var fn = et.GetFunctionName();\n    if (fn == null) continue;\n    var dbFn = et.Model.FindDbFunction(fn);\n    if (dbFn != null && dbFn.Parameters.Count > 0)\n        throw new InvalidOperationException($\"Mapped DbFunction {fn} must be parameterless\");\n}","typeGuard":"static bool IsParameterless(MethodInfo m) => m.GetParameters().Length == 0;","tryCatchPattern":"try { _ = ctx.Model; } catch (InvalidOperationException ex) when (ex.Message.Contains(\"doesn't have any parameters\")) { /* remove parameters from the mapped DbFunction */ }","preventionTips":["Use a dedicated parameterless method for entity mapping; keep parameterized DbFunctions as query operators only.","Review DbFunction method signatures during code review for accidental parameters."],"tags":["ef-core","dbfunction","mapping","parameters","model-validation"],"analyzedSha":"dbf9771522148d61a2467854921bd5dc6f6e6916","analyzedAt":"2026-08-06T20:46:03.226Z","schemaVersion":2},"datasetVersion":"2026-08-07T03:17:09.362Z"}