Problem in calling unmanaged win32 dll in webservice code

Discussion in 'ASP .Net Web Services' started by tomar, Oct 17, 2007.

  1. tomar

    tomar Guest

    Hi All,

    I Made a win32 dll named with Test.dll in VC++6.0 using following code

    ** FUNCTION: ASum
    extern "C" __declspec(dllexport) int ASum(int a, int b)
    return (a+b);

    When I Use this Test.dll (Unmanaged code) in WebService(Managed code)
    written in C# like

    public class AldorWeb : System.Web.Services.WebService
    [DllImport("Test.dll", SetLastError = false)]
    public static extern int ASum(int a,int b);

    public AldorWeb()
    //CODEGEN: This call is required by the ASP.NET Web
    Services Designer
    public bool SUM()
    int x = ASum(2, 3);
    catch(Exception e)
    LogWriter.WriteLog(1, 1, (int)enLogType.eTraceLog,e.ToString());

    it gives error like "Unable to load DLL (Test.dll)." if I call SUM
    webmethod. while same code in Windows Application is working fine.

    I think that Permission might be an issue but don't know how to
    implement it. I use Impersonation also but no benefit. even I tried to
    use this code using class library written in C# and called this
    library in webservice but useless.

    Please suggest me some solujtions.

    Thanks all.
    Dharmendra Singh Tomar
    Metadesign Solutions
    tomar, Oct 17, 2007
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  2. tomar

    tomar Guest

    Hi All,

    I have seen putting dll in System32 folder and in C drive as
    well.........Error remains same.

    Dharmendra Singh Tomar
    Metadesign solutions
    tomar, Oct 17, 2007
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  3. Did you place the dll in the bin\ directory?

    In fact, are you running VS2005 SP1, and is this an "ASP.NET Web Service
    Application", or did you create it with File->New->Web Site?

    Also, please include the entire, literal, exception that you receive.
    John Saunders [MVP], Oct 17, 2007
  4. tomar

    tomar Guest

    Hi John,
    First of all thanks for your quick response .My comments are
    below as the answer of your questions.

    1. Yes I have Placed the dll in bin\ directory.
    2. My Application is an webservice application.
    3. I am using Dotnet Framwork 1.1.4322.
    4. Exception : System.DllNotFoundException
    Message : Unable to load DLL (Test.dll).
    Is there any restriction in this version? As far as I think If we are
    calling functions of kernel32.dll, User32.dll and advapi32.dll.
    Application is working fine for these built in dll's. What can be the
    issue if I use User created Dll and this dll is perfectly loading in
    windows application in C#.

    Dharmendra Singh Tomar
    tomar, Oct 18, 2007
  5. tomar

    tomar Guest


    Hi all,

    I got the Problem, Actually this Project includes another project
    which creates .Lib file as output So dependency of this project is on
    other project. If I remove All the dependency It gets Called fine. But
    Problem Is here that I have to call this dll with dependency on .Lib
    file. I put that Lib file in webservice's bin folder with dll but same
    error comes.

    Please help me to resolve this issue.

    Dharmendra Singh Tomar
    MetaDesign Solutions
    tomar, Oct 18, 2007
  6. tomar

    tomar Guest



    I am not getting whts happening.

    1. Its not a security issue bcos DLL is being loaded successfully if
    there is no dependency on other file
    2. In Windows application without including LIB dll is being loaded
    and function is called successfully.

    Dharmendra Singh tomar
    MetaDesign Solutions
    tomar, Oct 18, 2007
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