How retrieve directory of the assembly

Question

In order to call a webservice, I've created a DLL in C# .NET 2.0 .

After registering the DLL in SQL Server 2008 R2, I tried, in this DLL, to retreive its directory in order to load a configuration file.

The problem is all methods I found on Google doesn't work, and it's a problem because I can't load the file. I don't want put some "hard paths" in my code, because it can change depending of the environment.

There is how I register my dll in SQL Server 2008 :

DROP FUNCTION [Tools].[CallWriteDepot]
GO
DROP FUNCTION [Tools].[CallExtractDepot]
GO
drop assembly SqlAssembly
go

create assembly SqlAssembly
from 'C:\webservices\dll\SqlAssembly.dll'
with permission_set = unsafe
go
---------------------------------------------------------------------------------------------------
CREATE FUNCTION [Tools].[CallWriteDepot](@xmlInputFile [nvarchar](max))
RETURNS [nvarchar](max) WITH EXECUTE AS CALLER
AS 
EXTERNAL NAME [SqlAssembly].[SqlAssembly.Main].[writeToSafe]
GO

---------------------------------------------------------------------------------------------------
CREATE FUNCTION [Tools].[CallExtractDepot](@xmlInputFile [nvarchar](max))
RETURNS [nvarchar](max) WITH EXECUTE AS CALLER
AS 
EXTERNAL NAME [SqlAssembly].[SqlAssembly.Main].[readFromSafe]
GO

As you see, the DLL is in C:\webservices\dll\SqlAssembly.dll and it is impossible to find this path in the DLL code, as you can see below.

There is the result after few tests :

Assembly.GetAssembly(typeof(SqlAssembly.Main)).CodeBase
Result : empty
attrTest2.Value = Assembly.GetAssembly(typeof(SqlAssembly.Main)).Location
Result : empty
Assembly.GetCallingAssembly().Location
Result : C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\Binn\SqlAccess.dll
Assembly.GetCallingAssembly().GetName().CodeBase
Result : file:///C:/Program Files/Microsoft SQL Server/MSSQL10_50.MSSQLSERVER/MSSQL/Binn/SqlAccess.DLL
Assembly.GetExecutingAssembly().Location
Result : empty
Assembly.GetExecutingAssembly().GetName().CodeBase
Result : empty
Directory.GetCurrentDirectory();
Result : C:\Windows\system32
AppDomain.CurrentDomain.BaseDirectory;
Result : C:\Program Files\Microsoft SQL Server\MSSQL10_50.MSSQLSERVER\MSSQL\Binn\
Environment.CurrentDirectory;
Result : C:\Windows\system32

If anybody knows how SQL Server register a DLL function ? It's like it save the function in a memory zone and don't read the dll file anymore.

If anybody have the solution too ;)

Answer 1

When you create an assembly in SQL Server the binary code of the dll is loaded into SQL Server. You can find it in sys.assembly_files. The dll used to create the assembly is not used when you execute functions in the assembly.

A possible solution to your problem could be to have an .ini file that contains the path to the configuration file. Just make sure you put your .ini file in a place you can find it through the path environment variable.