How to fix Error 11518 on Windows Server 2025 / Windows 11

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Troubleshooting Guide: SQL Server Error 11518 — CLR Trigger Metadata Resolution Failure

Why This Error Happens

This error occurs because SQL Server’s metadata resolution engine cannot statically determine the schema of a result set when a stored procedure or statement invokes a CLR (Common Language Runtime) trigger. Since CLR triggers execute managed .NET code rather than native T-SQL, the query optimizer cannot inspect the trigger’s internal logic at compile time to infer column names, types, or nullability. This typically surfaces when tools like sys.dm_exec_describe_first_result_set, SSDT schema comparisons, or client drivers request metadata for a procedure that touches a table with an attached CLR trigger.

Step-by-Step Resolution Guide

Step 1: Identify the Procedure and Trigger Causing the Error

  • Run the following query to locate CLR triggers in the affected database:
  SELECT t.name AS TriggerName, OBJECT_NAME(t.parent_id) AS TableName
  FROM sys.triggers t
  WHERE t.is_disabled = 0 AND t.type = 'TA';
  • Cross-reference the procedure name from the error message (%.*ls) with sys.sql_modules to confirm which statement is triggering the metadata lookup failure.

Step 2: Use WITH RESULT SETS or Explicit Schema Definition

  • Since SQL Server cannot infer metadata automatically, explicitly define the expected result set when calling the procedure:
  EXEC YourProcedure
  WITH RESULT SETS
  (
      (ColumnA INT, ColumnB NVARCHAR(100))
  );
  • This bypasses the need for SQL Server to auto-discover metadata through the CLR trigger path.

Step 3: Set FMTONLY or Metadata Discovery Options Appropriately

  • For legacy compatibility, ensure SET FMTONLY OFF is used only in contexts where it won’t trigger unwanted execution (avoid in production due to deprecated behavior in newer builds).
  • In application connection strings using .NET SqlClient on Windows Server 2025, disable automatic metadata discovery by setting SqlCommandBuilder.DeriveParameters manually instead of relying on implicit calls.
  • If using SSDT or Entity Framework scaffolding, configure the model to skip automatic metadata inference for affected stored procedures by manually mapping result columns in the .edmx or Fluent API configuration.

Step 4: Review and Isolate the CLR Trigger Logic

  • Open the CLR trigger assembly in Visual Studio and confirm it does not perform dynamic SQL execution or conditional schema changes, as this exacerbates metadata ambiguity.
  • If possible, refactor the trigger logic into a T-SQL trigger wrapper calling a CLR function instead of using a full CLR trigger, since T-SQL triggers allow proper metadata inference.

Step 5: Update SQL Server 2025 Cumulative Update

  • Check your current build with:
  SELECT @@VERSION;
  • Apply the latest Cumulative Update (CU) from Microsoft, as metadata resolution for CLR objects has received incremental fixes in SQL Server 2025 servicing releases.

Alternative or Verification Steps

  • Verify the fix by re-running the original failing query or application call with SQL Server Profiler/Extended Events active, confirming Error 11518 no longer appears in the error log.
  • As an alternative, if refactoring the CLR trigger isn’t feasible, instruct client applications to request results using SET NOCOUNT ON combined with explicit WITH RESULT SETS definitions on every call, which avoids SQL Server’s automatic metadata discovery path entirely.