Develop Reference

Unmanaged signature when importing Visual c++ DLL in c#

I have a DLL that was developed in Visual C++, and I've started importing it's functionality to a c# project using DllImport. I've already implemented a few methods and they work well.
For that specific method I'm getting the following error:
Additional information: A call to PInvoke function 'SdkTest!SdkTest.Program::CLIENT_RealPlay' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.
The c++ method I'm trying to implement has this signature:
CLIENT_NET_API LLONG CALL_METHOD CLIENT_RealPlay(LLONG lLoginID, int nChannelID, HWND hWnd);
With the following definitions:
#define CLIENT_NET_API __declspec(dllimport)
#define CALL_METHOD __stdcall
#define LLONG LONG
My c# impelmentation is the following:
[DllImport("dhnetsdk.dll")]
public static extern long CLIENT_RealPlay(long lLoginID, int nChannelID, IntPtr hWnd);
(I've read that HWND equivalent in c# is IntPtr, but I've also tried to put int, long, object...)
I also tried doing DllImport in the following way (As suggested in some posts and worked for some other methods I'm using):
[DllImport("dhnetsdk.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
No matter what I try I'm getting the same error. What am I miss understanding? If an internal exception in the c++ code is thrown, what kind of exception will I get in my code?

#define LLONG LONG
Now, LONG maps to long, which is a signed 32 bit type on Windows. Therefore, using long in your C# code is wrong because C# long is a 64 bit type. You need to use int instead. Like this:
[DllImport("dhnetsdk.dll")]
public static extern int CLIENT_RealPlay(int lLoginID, int nChannelID, IntPtr hWnd);

The c++ function is declared with calling convention stdcall, but you are calling it with cdecl.
In my experience, call stack corruptions are mostly caused by using the wrong calling convention.

typedef void* alternative in c#

I am using DLL runtime which is made with C language into C#.
I came across below statement.
typedef void *JCCP_PROPERTY_HANDLE;
In function it is being used as:
JCCP_RESULT __JCCP_FUNCTION__ jccpGetProperty(
JCCP_HANDLE hjccp,
const char *name,
JCCP_PROPERTY_HANDLE *phproperty);
Now I want to call jccpGetProperty() method in my C# code.
Can anybody tell how can I pass third parameter(JCCP_PROPERTY_HANDLE *phproperty) to function from C#.
I tried with below code but not working.
Extern Method:
[DllImport(DLL_NAME, EntryPoint = "_jccpGetProperty", CallingConvention = CallingConvention.Cdecl)]
public static extern IntPtr jccpGetProperty(IntPtr hjccp, string name, ref IntPtr JCCP_PROPERTY_HANDLE);
Usage
IntPtr handle = IntPtr.Zero;
string tag = "server.version";
var result = jccpGetProperty(hjccp, tag, ref handle);
Can anybody help me in this?

IntPtr is the correct type mapping for void*. The native type void* is generally used for an opaque pointer, and that is mapped to IntPtr in C#.
Those parts of the p/invoke declaration that we can verify are correct. The unverifible parts are:
The calling convention. You believe that it is cdecl, but we can't check.
The return type. You believe it to be pointer sized. Again we cannot check. My guess is that a 32 bit integer, int or uint is more likely. That would make a difference in a 64 bit process.
The values passed to the function. It's perfectly possible that the function is declared correctly, but you are passing invalid values.
Because you only showed partial code and details, it's hard to say much more. You will have to verify all the parts of the program that we cannot.
I suggest that you start with working C or C++ code and translate that, looking for the first point of deviation in behaviour between that code and your C# translation.

How to marshal two dimensional TCHAR array?

I have a DLL function in that converts a file to another format.
The function produces multiple files as output.
Therefore, it fills the 2nd parameter with the paths of the output files.
The C++ function is defined as the following:
int Convert(LPTSTR lpSource, TCHAR outputFileName[][MAX_PATH]);
How do I mashal the 2nd parameter so that my C# application can receive the output file paths correctly?
[DllImport("Convert.dll")]
private static extern int Convert(
[MarshalAs(UnmanagedType.LPTStr)] string lpszSource,
????
);
Thanks in advance.

I would make things simpler using C++/CLI (which is very good at building bridging layers between native C/C++ code and managed code).
Basically, you could write a thin C++/CLI layer that exposes a method that calls the native function in its body, and then copies the returned native strings into a gcnew-ly created array<String^>, and returns it to the C# managed caller.

I finally figured it out.
I changed my C++ function to the following:
int Convert(LPTSTR lpSource, LPTSTR *plpOutputFileName, int size);
And the C# declaration as:
[DllImport("Convert.dll")]
private static extern int Convert(
[MarshalAs(UnmanagedType.LPTStr)] string lpszSource,
[In, Out] String[] outputFileName,
int size
);
Thank you all for helping.

How would you declare DLL import signature?

this is a follow-up post of Using pHash from .NET
How would you declare following C++ declaration in .NET?
int ph_dct_imagehash(const char* file,ulong64 &hash);
So far i have
[DllImport(#"pHash.dll")]
public static extern int ph_dct_imagehash(string file, ref ulong hash);
But I am now getting following error for
ulong hash1 = 0, hash2 = 0;
string firstImage = #"C:\Users\dance2die\Pictures\2011-01-23\177.JPG";
string secondImage = #"C:\Users\dance2die\Pictures\2011-01-23\176.JPG";
ph_dct_imagehash(firstImage, ref hash1);
ph_dct_imagehash(secondImage, ref hash2);
It basically says that my declartion of ph_dtc_imagehash is wrong.
What am I doing wrong here?

Stack imbalance indicates that the C++ code uses cdecl and your C# uses stdcall calling convention. Change your DLLImport to this:
[DLLImport(#"pHash.dll", CallingConvention=CallingConvention.Cdecl)]
The function signature in C# (return value and parameters) is otherwise correct.

Check the calling convention. If you don't specify one on the DllImport attribute, it defaults to WinApi (stdcall). The C snippet you posted doesn't specify a calling convention, and at least in VC++ the default calling convention is cdecl.
So you should try:
[DllImport(#"pHash.dll", CallingConvention=CallingConvention.Cdecl)]
public static extern int ph_dct_imagehash(string file, ref ulong hash);

Try explicitly setting DllImportAttribute.CharSet property to CharSet.Auto as if you don't specify it, it will default to Ansi. This may be causing issues as your declaration seems to be fine.
Even if this is not the issue, take habit of specifying the CharSet property whenever a Dll function deals with text.

PInvoke in 64bit .net app through c++ 64 bit dll

I'm having an issue calling a function in a c++ dll inside of a c# app. I'm calling the function inside of c# like so:
[DllImport("cryptopp.dll")]
public static extern IntPtr RSAEncryptString(string filename, string seed, string message);
It is being exported in the c++ dll as shown below.
extern "C" __declspec(dllexport) const char* __cdecl RSAEncryptString(const char *pubFilename, const char *seed, const char *message);
What I get when I try to call this, however, is an "An External component has thrown an exception." exception, which is not very descriptive at all, and extremely unhelpful.
When I pull up the dll in an export viewer, it shows all the other exported functions with fully quantified declarations (I.E. public: void __cdecl CryptoPP::X509PublicKey::`vbase destructor'(void) __ptr64 ) , except for the function I am calling, which just displays the function name RSAEncryptString.
This is the only possible issue I can see, besides maybe mis-calling the function with an invalid declaration on the c# side. Am I using System.Runtime.InteropServices.Marshal wrong?
Please help <3 and thanks in advance.

I think you need to change the first line to:
[DllImport("cryptopp.dll",
CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
If you want to get very descriptive, you can also add these:
public static extern IntPtr RSAEncryptString(
[In, MarshalAs(UnmanagedType.LPStr)] string filename,
[In, MarshalAs(UnmanagedType.LPStr)] string seed,
[In, MarshalAs(UnmanagedType.LPStr)] string message);
IIRC think the CharSet should take care of the encoding thing for you, but if it doesn't, use the MarshalAs also, as shown above.
Edit:
Oh I think I got why you still get an error! Your code still had the above problems, but it's still erring because you can't return a string object since it's not a managed object; you need to return a pointer (like IntPtr) and then use Marshal.PtrToStringAnsi!
(I didn't really look at your return type when answering this at first.)

It appears you're trying to store the return value of type const char * (an LPCSTR) into an IntPtr type (usually used for HANDLEs, not LPSTRs.) Try this:
[DllImport("cryptopp.dll", CharSet = CharSet.Auto)]
public static extern String RSAEncryptString(String filename, String seed, String message);
Also keep in mind that if any argument is getting written to, you'll need to add out before its type, i.e. ..., out String message)