Unable to call the DLL from ASP.NET

Question

Hi I have a C Dll which will interact with a cobol application. we want to send the data to the cobol through internet.

so i created an C# DLL which will call the C DLL. its working fine when i do a consoleapp, but when i try to call the same DLL from ASP.NET its giving error message

i dont understand that error

An attempt was made to load a program with an incorrect format. (Exception from HRESULT: 0x8007000B)

There are some other posts regarding this but those were not matching my context i think im missing permissions for asp.net

this is the declaration in my c# dll for calling c dll

[DllImport(@"C:\CCExpert\haz450cp.dll", EntryPoint = "Methodname", CallingConvention = CallingConvention.Cdecl)]
    unsafe public static extern void Methodname(ref p1, ref p2);

Edit:

Hi i changed the settings according to your suggestions but now im getting a new error

Microsoft Visual Studio C Runtime Library has detected a fatal error in w3wp.exe

Answer 1

If you have a C .dll, it'll be either 32-bit or 64-bit. You must make sure that your site is running in the correct platform for that (that is, your site is running as a matching 32/64-bit site.)

In IIS 7, you can configure the bitness of the application pool by right-clicking the app pool and selecting Advanced Settings . There's a setting called Enable 32-bit applications , you need to set that to True for 32-bit sites and False for 64-bit sites.

You can use Dependency Walker to see if the DLL is 32-bit or 64-bit: use View full paths (looks like C:\\ on the toolbar) and if the dependencies of your .dll and:

• If you have a 32-bit OS, your .dll may be 64-bit. You won't be able to load it.
• If you have a 64-bit OS:
  • If the dependencies are under System32, it's a 64-bit .dll
  • If the dependencies are under SysWOW64, it's a 32-bit .dll

That tells you how to set the application pool. To set the app pool you can check this link .

Make sure you use Advanced Settings when you open the app pool properties, not basic settings. Also, these settings are not available when you bring up properties for your site - they are only available for the app pool.

Answer 2

The most likely cause of this problem is that you are trying to load a 32 bit DLL into a 64 bit process (or vice versa). To verify or rule this out check and see if the Asp.Net is running in 64 bit mode and if so you need to have a 64 bit version of the C DLL