"The specified procedure could not be found" error with .NET 4
.net, dll, dllimport
Solution
Problem solved. Some things to note as I went through troubleshooting steps, for those who stumble upon this in the future.
- This error does not necessarily mean it can't find procedure `X` -- rather it may mean it can't find function `Y`, from another dll, that is called by `X`.
- Make sure to compile the DLL in 'Release' mode, as the C++ redistributable will not include the debug DLLs.
- Start with a shell function, and add pieces back in, one by one.
In my above test example, the problem was I was compiling as a Debug version.
However, in my complete function, that change did not fix the issue. It turns out I was missing some DLLs that dependency walker did not catch.
Problem
I am developing on a 64-bit Windows 7 box with Visual Studio 2012 (11.0.51106.01 Update 1). I have a Support project that compiles some C code into a (32-bit) DLL. In my header I have: ``` #define RET_TYPE(type) _declspec(dllexport) type __stdcall RET_TYPE(int) test_dll_call(int invar); ``` In my C file I have: ``` RET_TYPE(int) test_dll_call(int invar) { int retVal = 4 * invar; return retVal; } ``` I also have a (32-bit) WPF C# application that loads the DLL inside of a class as follows: ``` [DllImport("MyDll.dll", CharSet = CharSet.Ansi, BestFitMapping = true, ThrowOnUnmappableChar = true)] public static extern int test_dll_call(int invar); ``` This is wrapped as follows: ``` public void Wrap_TestDllCall() { try { int outTest = 0; int invar = 3; outTest = test_dll_call(invar); } catch (Exception ex) { dllError = ex.ToString(); } } ``` When I run this in the debugger on my development box, this works fine. If I copy all the relevant files to a separate folder and run it from there, it works fine. If I copy all the necessary folders to another computer running 32-bit Windows XP SP3 I get the following error: ``` System.DllNotFoundException: Unable to load DLL 'MyDll.dll': The specified procedure could not be found. (Exception from HRESULT: 0x8007007F) at MyNamespace.MyClass.test_dll_call(Int32 invar) at MyNamespace.MyClass.Wrap_TestDllCall() ``` I have used dependency walker on both my compiled exe and the dll; the only missing dlls it found were `wer.dll` and `ieshims.dll`, which from my research are not needed on XP. I have installed the VS2012 C++ Redistributable, and .NET 4, and the .NET 4.0.3 update. Still no luck. Edit As Hans points out, this appears to be that the app can't find the procedure in the DLL; I have also tried: ``` [DllImport("MyDll.dll", CallingConvention=CallingConvention.Cdecl)] public static extern int test_dll_call(int invar); ``` and ``` __declspec(dllexport) int __cdecl test_dll_call(int invar); ``` Which also works fine on my dev box but gives the same error on the WinXP box. Help!