Accessing Native Code from a CLR UDF

This example shows how to invoke a function in native (unmanaged) C++ code from a user-defined function in an assembly, in your database.

For this example, the working directory should be c:\test.

First compile the C++ code:

// Win32Sleep.cpp  
// compile with: /LD /link /noentry kernel32.lib  
#include <windows.h>  
  
extern "C"  
__declspec( dllexport ) void _cdecl SleepyLoop(DWORD sleep_interval) {  
   Sleep(sleep_interval);  
}  

Next, compile the C# code to an assembly:

// proc.cs  
// compile with: /target:library  
using System;  
using System.Threading;  
using System.Data.Sql;  
using System.Runtime.InteropServices;  
  
public class StoreProcedures {  
  
   public static readonly uint SLEEP_LOOP_TIMES = 10;  
   public static readonly uint SLEEP_DURATION = 1000;  
  
   [DllImport(@"c:\test\Win32Sleep.dll")]  
   internal static extern void SleepyLoop(uint sleepInterval);  
  
   public static void SleepInProcedure(int loopTimes) {  
      for ( int i = 0 ; i < loopTimes ; i++ ) {  
         // invoke the unmanaged routine  
         SleepyLoop(SLEEP_DURATION);  
      }  
   }  
}  

Finally, execute the following Transact-SQL:

USE MASTER  
GO  
  
IF DB_ID('testdb') IS NOT NULL  
DROP DATABASE testdb  
GO  
  
CREATE DATABASE testdb  
GO  
  
USE testdb  
GO  
  
ALTER DATABASE testdb SET TRUSTWORTHY ON   
GO  
  
sp_configure 'show advanced options', 1  
GO  
RECONFIGURE  
GO  
sp_configure 'clr enabled', 1  
GO  
RECONFIGURE  
GO  
  
CREATE ASSEMBLY myasm FROM 'c:\test\proc.dll' WITH PERMISSION_SET=UNSAFE   
go  
  
CREATE PROCEDURE SleepProc(@loopTimes INT)  
AS EXTERNAL NAME myasm.[StoreProcedures].[SleepInProcedure]  
go  
  
-- sleep 5 seconds  
EXEC SleepProc 5  
GO  

See Also

Usage Scenarios and Examples for Common Language Runtime (CLR) Integration