How to fix Error 6295 on Windows Server 2025 / Windows 11

by

Troubleshooting Guide: SQL Server Error 6295 — Invalid SqlFacetAttribute Property Value

Why This Error Happens

This error occurs when a CLR user-defined type (UDT) or user-defined function registered in SQL Server 2025 contains a SqlFacetAttribute with a property value that falls outside the acceptable range defined by SQL Server’s metadata validation rules. Common culprits include negative or zero values for MaxSize, invalid Precision/Scale combinations that exceed SQL Server’s numeric limits, or incompatible settings like IsFixedLength = true combined with MaxSize = -1. This is almost always a code-level issue introduced during CLR assembly compilation rather than a server configuration problem, meaning the assembly was built with attribute values that violate SQL Server’s internal consistency checks during CREATE TYPE, CREATE ASSEMBLY, or CREATE FUNCTION operations.

Step-by-Step Resolution Guide

Step 1: Identify the Offending Assembly and Type

  • Open the full error message in SQL Server Management Studio (SSMS) or the SQL Server error log located at C:\Program Files\Microsoft SQL Server\MSSQL17.MSSQLSERVER\MSSQL\Log\ERRORLOG.
  • Note the three-part identifier in the error (database.schema.object) to locate the exact CLR type or function being registered.
  • Run SELECT * FROM sys.assembly_types WHERE assembly_id = <id>; to cross-reference the object with its source assembly.

Step 2: Inspect the SqlFacetAttribute Source Code

  • Open the .NET project source code (Visual Studio 2022/2026) that defines the CLR UDT or UDF.
  • Locate the [SqlFacet(...)] attribute decoration on the class or method in question.
  • Check for invalid combinations such as:
  • MaxSize set to 0 or a value less than -1.
  • Precision greater than 38 or Scale greater than Precision.
  • IsFixedLength = true paired with MaxSize = -1 (which implies MAX/unbounded length).
  • Correct the invalid property (e.g., change MaxSize = -5 to MaxSize = 8000).

Step 3: Rebuild and Redeploy the Assembly

  • Recompile the .NET assembly using dotnet build or Visual Studio’s Build menu.
  • Drop the broken assembly in SQL Server: DROP ASSEMBLY YourAssemblyName; (you may need to drop dependent types/functions first).
  • Re-register the corrected assembly:
  CREATE ASSEMBLY YourAssemblyName
  FROM 'C:\Deploy\YourAssembly.dll'
  WITH PERMISSION_SET = SAFE;
  • Re-create the CLR type or function referencing the updated assembly.

Step 4: Validate Server-Level CLR Configuration

  • Confirm CLR integration is enabled on the instance:
  EXEC sp_configure 'clr enabled', 1;
  RECONFIGURE;
  • On Windows Server 2025/Windows 11, verify .NET Framework/CLR hosting components are current via Windows Update, since outdated CLR hosting binaries can sometimes cause attribute metadata to be misread.

Alternative or Verification Steps

  • Verify the fix by re-running the original CREATE TYPE, CREATE ASSEMBLY, or CREATE FUNCTION statement — it should complete without Error 6295, and SELECT * FROM sys.assembly_types; should list the object correctly.
  • If the error persists, use ildasm.exe (IL Disassembler) on the compiled DLL to inspect the raw SqlFacetAttribute metadata and confirm no stale or cached build artifacts are being deployed instead of your corrected source.