I'm rewriting some C++ code to C#. The code I'm refactoring uses AddIPAddress in C++ but I cannot find a way to do the same in C#. Can anyone help?
You can use P/Invoke to call the method directly. This page has the details (and a sample) of how you can go about that.
The basic idea is to create a C# method that corresponds to the native method by declaring it as extern, and decorating it with the DllImport attribute:
DllImport("iphlpapi.dll", EntryPoint = "AddIPAddress", SetLastError = true)]
private static extern UInt32 AddIPAddress(UInt32 Address, UInt32 IpMaskint, int IfIndex, out int NTEContext, out int NTEInstance);
Related
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
pinvokestackimbalance — how can I fix this or turn it off?
I need to access a c++ dll library (I don't have the source code) from c# code.
for example the following functions:
UINT32 myfunc1()
UINT32 myfunc2(IN char * var1)
UINT32 myfunc3(IN char * var1, OUT UINT32 * var2)
For myfunc1 I have no problems when I use the following code:
[DllImport("mydll.dll")]
public static extern int myfunc1();
On the other hand I was unable to use myfunc2 and myfunc3.
For myfunc2 I tried the following: (and many others desperately)
[DllImport("mydll.dll")]
public static extern int myfunc2(string var1);
[DllImport("mydll.dll")]
public static extern int myfunc2([MarshalAs(UnmanagedType.LPStr)] string var1);
[DllImport("mydll.dll")]
public static extern int myfunc2(char[] var1);
But all of them gave the following error:
"Managed Debugging Assistant 'PInvokeStackImbalance' has detected a problem in 'C:\Users\....\myproject\bin\Debug\myproj.vshost.exe'.
Additional Information: A call to PInvoke function 'myproject!myproject.mydll::myfunc2' 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."
Please, guide on what I should do.
Your C++ functions use the cdecl calling convention, but the default calling convention for DllImport is stdcall. This calling convention mismatch is the most common cause of the stack imbalanced MDA error.
You fix the problem by making the calling conventions match. The easiest way to do that is to change the C# code to specify cdecl like this:
[DllImport("mydll.dll", CallingConvention=CallingConvention.Cdecl)]
public static extern int myfunc2(string var1);
It might just be a character set mismatch try this
[DllImport("mydll.dll", CharSet = CharSet.Ansi)]
public static extern int SendText([MarshalAs(UnmanagedType.LPStr)] string var1);
Nicked from:
DLL import char * pointer from C#
I have used DLL Export viewer to try and find the functions that are in this DLL, I have found a list of functions and here it is:
public: int __thiscall CSTVdsDisk::GetPartitionCount(void);
the question is within in C# I am not able to call the function using either:
[DllImport("Some.dll",
ExactSpelling = true,
EntryPoint = "GetPartitionCount",
CallingConvention = CallingConvention.StdCall,
SetLastError = true)]
or:
[DllImport("Some.dll",
ExactSpelling = true,
EntryPoint = "CSTVdsDisk::GetPartitionCount",
CallingConvention = CallingConvention.StdCall,
SetLastError = true)]
private static extern int GetPartitionSize();
They all fail. Is there something that I am doing wrong? Can anyone help? Thanks!
You can't call that function using P/Invoke. The __thiscall calling reference means that this function is a class member function. It is a member function of the CSTVdsDisk class.
To be able to call the function you will have to create an instance of the CSTVdsDisk class and call GetPartitionCount from that instance.
You'll have to do that in C++ or C++/CLR as you can't create a C++ class in C#. See also Create unmanaged c++ object in c#.
Based on the name, that appears to be a C++ class method. That is going to make it very difficult to call that method directly from P/Invoke for two reasons:
You need to find the "real" name; the Export Viewer is apparently showing up the unmangled name, but the actual C++ function name will look much uglier, like #0GetPartitionCount#CSTVdsDisk##QPBAEXA or similar. You may need to use a lower-level tool like dumpbin to find that name.
You need to fake the "thiscall" style call; this means you need to pass an instance of a C++ class as the first parameter. This is only going to work if the C++ class constructor is also exposed from the DLL; in which case, you can call the class constructor, store the result in an IntPtr, and pass it to every subsequent call. (If the constructor is exposed as a DLL export its mangled name will start with ??, like `??0CSTVdsDisk##QAE#ABV0##Z
This CodeProject article shows you how to do most of that, but it's pretty fragile, so expect problems. I'd strongly suggest you look for a non-C++ library that does something similar, or at least one that's designed to be usable from C code.
In your native code, make sure you're exporting the function. By default you function wont be listed in the Exports table so you need to mark it so that the compiler knows to export it. You also need to mark the function as
extern "C"
so that the compiler doesn't mangle the name.
Typically I define the following macro:
#define DLLEXPORT extern "C" __declspec(dllexport)
to handle all of this, and then simply declare exported functions like:
DLLEXPORT __cdecl int Example(int x, int y)
If you find you're still having troubles with the name, try using a free PE explorer program on the dll and checking the exported function table for the correct name.
I can't find any example signatures for .NET to use this function (GetSystemDEPPolicy).
http://msdn.microsoft.com/en-us/library/windows/desktop/bb736298(v=vs.85).aspx
It's a fairly simple function but I don't know how to create the signature to call it. Can someone please help?
GetSystemDEPPolicy is defined as
DEP_SYSTEM_POLICY_TYPE WINAPI GetSystemDEPPolicy(void);
and DEP_SYSTEM_POLICY_TYPE is an enum (see winbase.h assuming you have the C++ components installed in your development environment - if not try winbase.h) and enums in C default to int, as such I would go with
[DllImport("kernel32.dll", CharSet=CharSet.Auto, ExactSpelling=true)]
public static extern int GetSystemDEPPolicy();
May I recommend you follow this tutorial on PInvoke
The question is easy, Want to read a string from managed C# code to my unmanaged C++ code in WCHAR* [].
The C function is:
extern "C" __declspec(dllexport) int __cdecl myfunc(int argc, WCHAR* argv[])
and in C# I imported the DLL:
[DllImport("mydll.dll", CharSet = CharSet.Auto, SetLastError = true, CallingConvention = CallingConvention.Cdecl)]
public static extern int myfunc(int argc, [MarshalAs(UnmanagedType.LPTStr)] StringBuilder str);
I run, but when I tried to read the string in my C++ code I get AccessViolationException : Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
What is the correct way to do this and vice versa (i.e. passing a string from C++ unmanaged to C# managed code)?
Help Appreciated.
Thanks
It seems that your C function expects an array of strings, and you're passing a single string instead.
I haven't used P/Invoke myself, but this question might provide some insight.
I am not sure about C# to C++ but i can help you out in your C++ to C# problem.
Export the function from C++ code like this:
DllExport std::string MyFunction( std::string MyParameter) ;
This can be imported in your C# code as:
[DllImport("DLLName.dll", EntryPoint = "MyFunction", CallingConvention = CallingConvention.StdCall, CharSet = CharSet.Ansi)]
[return: MarshalAs(UnmanagedType.LPStr)]
public static extern string MyFunction([System.Runtime.InteropServices.InAttribute()] [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.LPStr)] string MyParameter);
Now, in your C# code the function "MyFunction" will take in a string and return a string. You can then call MyFunction and the operations can be carried out.
If you are using a WCHAR*, perhaps you should try marshalling as UnmanagedType.LPWStr instead to avoid passing half as much memory as expected?
The documentation on Default Marshaling for Strings should provide you with more details.
I'm working on a C# application that supports two communications interfaces, each supported by its own DLL. Each DLL contains the same function names, but their implementation varies slightly depending on the supported interface. As it is, users will typically have only one DLL installed on their machine, not both. The DLL for the old interface is imported like this:
[DllImport("myOldDll.dll",
CharSet = CharSet.Auto,
CallingConvention = CallingConvention.StdCall)]
public static extern int MyFunc1( void );
public static extern int MyFunc2( void );
public static extern int MyFunc3( void );
Would this be a valid way to attempt to bring in either DLL?
[DllImport("myOldDll.dll",
CharSet = CharSet.Auto,
CallingConvention = CallingConvention.StdCall)]
[DllImport("myNewDll.dll",
CharSet = CharSet.Auto,
CallingConvention = CallingConvention.StdCall)]
public static extern int MyFunc1( void );
public static extern int MyFunc2( void );
public static extern int MyFunc3( void );
Ideally, I suppose it would be nice to detect a missing DLL and load the second DLL if the attempt to load the first fails. Is there a graceful way to do that?
How about doing a P/Invoke to `LoadLibrary'?
In .NET 1.1 you would need to create a proxy unmanaged DLL (write it in C or Delphi or ... ) and call it's methods, and that unmanaged DLL would do the rest. In .NET 2.0 and later you use Assembly.LoadFile() and further. Not as elegant as just declarations you attempted to use, and requires quite a lot of coding. So I'd suggest a proxy way if possible.
Perhaps you should give the methods imported from either DLL different names, and then have a delegate in your program that you point to one or the other (whichever is appropriate), and only call the delegate.
It sounds like you would be best served re-architecting to a modular plugin style interface.
There are a billion and a half examples of this on the web, like this one. In a nutshell though, you use LoadAssembly() on a directory of DLLs, then cast back to your common base interface.
I think I found a workable solution:
C# check that a file destination is valid
Thanks, everyone, for your input!