I wan to import a DLL and use its functions but i want to assign the dll to a value so i dont end up overiding methods
Example of how I want to do it
mydll = [DllImport("MyDll.dll")]
mydll.SayHi();
// So I don't override this:
public void SayHi() { Console.WriteLine("Hello!!!"); }
Any way to acheive this?
Import the DLL in a wrapper class.
using System;
using System.Runtime.InteropServices;
// Namespace is optional but generally recommended.
namespace MyDLLImports
{
static class MyDLLWrapper
{
// Use DllImport to import the SayHi() function.
[DllImport("mydll.dll", CharSet = CharSet.Unicode)]
public static extern void SayHi();
}
}
class Program
{
static void SayHi()
{
// whatever...
}
static void Main()
{
// Call the different SayHi() functions.
MyImports.MyDLLWrapper.SayHi();
SayHi();
}
}
See the MSDN docs on the DLLImport attribute for further details. You may also need to declare calling conventions, different character encodings, the DLL's main entry point, etc.
Related
I've written a simple C++/CLI DLL that has 2 public static methods:
namespace GetMscVerLib
{
public ref class CGetMscVer
{
static System::Int32 GetCompilerVersion ();
static System::Int32 GetCompilerFullVersion ();
};
}
I'm trying to call these methods from a C# console app in the same solution but the compiler doesn't recognize the methods and shows an error that says that the methods don't "exist in the current context":
namespace Get_MSC_VER
{
class Program
{
static void Main (string[] args)
{
Int32 i32CompilerVersion = CGetMscVer.GetCompilerVersion ();
Int32 i32CompilerFullVersion = CGetMscVer.GetCompilerFullVersion ();
}
}
}
What is the correct syntax? (online searches have produced pages of irrelevant links with some of the search keywords, assuming DllImport or COM). This seems like it should be quite a simple matter but finding it is not.
Thanks
First you need build your C++ program, you will get dll. Then you should create method with the same return value and add extern key word add DllImport attribute to your method. In your example method will look like this:
public class Program
{
static void Main(string[] args)
{
var version = GetCompilerVersion();
var fullVersion = GetCompilerFullVersion();
}
[DllImport("yourDllName.dll")]
public static extern int GetCompilerVersion();
[DllImport("yourDllName.dll")]
public static extern int GetCompilerFullVersion();
}
This should work. Because the methods are private by default c# wont allow you to access them.
namespace GetMscVerLib
{
public ref class CGetMscVer
{
public:
static System::Int32 GetCompilerVersion ();
static System::Int32 GetCompilerFullVersion ();
};
}
Another way, keeping everything static.
// C++/CLI DLL
namespace GetMscVerLib
{
public ref class CGetMscVer abstract sealed
{
public:
static System::Int32 GetCompilerVersion();
};
}
// C# assembly that references the C/C++ DLL
namespace Get_MSC_VER
{
class Program
{
static void Main (string[] args)
{
Int32 i32CompilerVersion = GetMscVerLib.CGetMscVer.GetCompilerVersion();
}
}
}
I have a problem with my compiler not being able to import kernel32.dll, althrough I'm using System.Runtime.InteropServices. Here is the Code:
using System;
...
using System.Runtime.InteropServices;
namespace server
{
class Debugconsole
{
public void Initialise()
{
[DllImport("kernel32.dll")]
...
}
}
}
It throws a whole bunch of syntaxerrors and "Can't find "DllImport" in current context."
Thanks for your help.
Attributes cannot be used inside a method.
You should move it out of your method:
class Debugconsole
{
[DllImport("kernel32.dll")]
... the static extern method declaration ...
public void Initialise()
{
...
}
}
I have a small DLL that has 3 functions : Init, Load and run.
I'm new with c# so as I read the questions here, I've opened a console project and wanted to load the DLL and use it's functions.
unfortunately - it didn't work. can anyone advise what went wrong?
This is the error I get:
Unable to find an entry point named 'Init' in DLL
'....path to my DLL....'.
this is the code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
namespace ConsoleApplication1
{
class Program
{
[DllImport("C:\\Desktop\\DLLTest.dll", CharSet = CharSet.Unicode)]
public static extern bool Init();
[DllImport("C:\\Desktop\\DLLTest.dll", CharSet = CharSet.Unicode)]
public static extern bool Load(string file);
[DllImport("C:\\Desktop\\DLLTest.dll", CharSet = CharSet.Unicode)]
public static extern bool Play();
static void Main()
{
Console.WriteLine("got till here!!!");
Init();
Load("C:\\Desktop\\the_thing_about_dogs_480x270.mp4");
Play();
}
}
}
The only thing I can suspect is maybe the fact that I'm not creating an instance?
besides that, no clue :(
* editing : *
this is the DLL :
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace DLLTest
{
public class DLLTestApi
{
myInfo localPlay;
public bool Init()
{
localPlay = new myInfo();
return true;
}
public bool Load(string file)
{
localPlay.Load(file);
return true;
}
public bool Play()
{
localPlay.StartNewThread();
return true;
}
public bool Stop()
{
localPlay.DxStopWMp();
return true;
}
public bool Pause()
{
localPlay.DxPause();
return true;
}
public bool Resume()
{
localPlay.DxResume();
return true;
}
public bool Close()
{
localPlay.DxClose();
return true;
}
}
}
The error message tells you clearly what the problem is. Your DLL does not export a function named Init. Possible reasons for this include:
The DLL is not an unmanaged DLL.
The DLL simply does not export a function of that name.
The DLL exports that function, but the name is decorated or mangled.
Probably the easiest way to diagnose the fault is to use a tool like Dependency Walker to inspect the DLL's exports.
Update
From the edit to the question, it is clear that item 1 is the reason. Your DLL is a managed DLL and it is incorrect to attempt to access it using p/invoke. Simply add it as a reference to your console application project.
To load a dll dynamically, not sure if it applies to a managed dll, use Assembly.LoadFrom() from System.Reflection;
To create an instance use Activator.CreateInstance() from System.Activator;
I'm trying to call a method, which is in a dll I've imported, from another class. Is there any way to do that? Thank you in advance!
To clarify myself: There is a class called "TTSManager". In this class a dll was imported. There also is a class "TTSdotNET" and in THIS class I would like to call a method within a dll, but the method isn't accessible. I hope somebody will help me.
P.S. I code in C#
"TTSManager":
using UnityEngine;
using System.Collections;
using System;
using System.Runtime.InteropServices;
public class TTSManager : MonoBehaviour
{
[DllImport ("SpeakerLib")]
private static extern void SpeakToSpeaker(string tts);
[DllImport ("SpeakerLib")]
private static extern void SpeakToFile(string tts, string fileName, string fileFormat); [DllImport ("SpeakerLib")]
private static extern void ReleaseSpeaker();
private static TTSManager instance = null;
private TTSManager(){}
public static TTSManager getInstance
{
get
{
if(instance == null)
{
instance = new TTSManager();
}
return instance;
}
}
// Use this for initialization
void Start ()
{
}
// Update is called once per frame
void Update ()
{
}
}
"TTSdotNET":
public class TTSdotNet : MonoBehaviour
{
void Update ()
{
if (Input.GetKey(KeyCode.F10))
{
SpeakToSpeaker("hello world i feel uncomfortable.");
}
}
}
I tend to create a separate static class for the DLL imports. In addition to importing the functions I mostly also create wrapper methods for each DLL function call.
Example:
internal static class NativeCalls
{
[DllImport ...]
private static extern int SomeFunctionCall(...);
public static int SomeFunction(...)
{
return SomeFunctionCall(...);
}
}
That way, any class can access the DLL and your problem is solved.
Currently I'm trying to use a C++ library under C# using DLL importation. Library is called Interception.
The problem is that I don't know how to translate #define entries and typedef declaration of the header file:
https://github.com/oblitum/Interception/blob/master/include/interception.h
I tried to use "using" directive, but with no success (I can't access to the void definition).
Moreover, I didn't understood the role of __declspec(dllimport) in this header. In my c# project, I just ignored it? Is it good to do that?
This is the code I want to use in c# (it's a sample of the library)
https://github.com/oblitum/Interception/blob/master/samples/hardwareid/main.cpp
EDIT:
What I've tried: basic importation:
[DllImport("interception.dll", CharSet = CharSet.Auto, SetLastError = true)]
void interception_set_filter(void* context, InterceptionPredicate predicate, ushort filter);
I don't know ho to convert InterceptionPredicate. According the header file, InterceptionFilter is a ushort, and InterceptionContext is a void pointer (void*).
The C++ library should be compiled as a .DLL file. This .DLL file should have exported functions. You can use the Depends tool to check what's exported from a .DLL. .NET code can call C++ exported functions using what's called "Platform Invoke".
Now, I strongly suggest you take a deep look at this Platform Invoke Tutorial that will guide you.
PS: void * should be declared in c# as IntPtr. enums should be redeclared as enums. Functions should be declared as static extern methods marked with the DllImport attribute.
First, it looks like you're trying to implement a global keyboard/mouse hook .. if that's the case, I'd recommend googling 'C# low level keyboard and mouse hook'.
Now for your question, first is the __declspec(dllimport) issue: this would be if you were actually using the header in a C++ application, that is the C++ equivilent of the C# DllImport .. so in effect you didn't ignore it, you implemented it. In C++ it just tells the linker that the function declared as such will be imported from a specific DLL instead of it being a local function (pretty similar to what the C# DllImport directive does)
Next is for function pointer issue (InterceptionPredicate). In the header it is defined as such:
typedef int (*InterceptionPredicate)(InterceptionDevice device);
And InterceptionDevice is just an 'int'. So the InterceptionPredicate is just a function pointer type (or Delegate in C#), so your delegate definition for InterceptionPredicate would look like this:
// [UnmanagedFunctionPointer(CallingConvention.Winapi)]
public delegate int InterceptionPredicate (int device);
A note about the UnmanagedFunctionPointer calling convention descriptor: IF you know what kind of calling convention (stdcall, fastcall, cdecl) the exported function might be using, you could specify here so that the .NET marshaler will know how to pass the data between the managed/unmanaged code, but if you don't know it or it's not specified typically you can just leave that off.
Also, as others have mentioned, unless you have the 'unsafe' flag specified in your C# properties, a void* type should always be an IntPtr in C#.
Also, be sure to mark the dll function in your C# code as public static extern, see example below.
So to make an example of the function you've specified, here's what could be done:
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
namespace InterceptorTest
{
public class Interceptor : IDisposable
{
#region DllImports
[DllImport("interception.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern IntPtr interception_create_context();
[DllImport("interception.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern void interception_destroy_context(IntPtr context);
[DllImport("interception.dll", CharSet = CharSet.Auto, SetLastError = true)]
public static extern void interception_set_filter(IntPtr context, InterceptionPredicate predicate, ushort filter);
// The function pointer type as defined in interception.h that needs to be defined as a delegate here
public delegate int InterceptionPredicate(int device);
#endregion
#region private members
private InterceptionPredicate m_PredicateDelegate { get; set; }
private IntPtr m_Context { get; set; }
#endregion
#region methods
public Interceptor(ushort filter)
{
// be sure to initialize the context
this.m_PredicateDelegate = new InterceptionPredicate(this.DoSomethingWithInterceptionPredicate);
this.m_Context = interception_create_context();
interception_set_filter(this.m_Context, this.m_PredicateDelegate, filter);
}
private void Cleanup()
{
interception_destroy_context(this.m_Context);
// the next line is not really needed but since we are dealing with
// managed to unmanaged code it's typically best to set to 0
this.m_Context = IntPtr.Zero;
}
public void Dispose()
{
this.Cleanup();
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (disposing) { this.Cleanup(); }
}
public int DoSomethingWithInterceptionPredicate(int device)
{
// this function is something you would define that would do something with
// the device code (or whatever other paramaters your 'DllImport' function might have
// and return whatever interception_set_filter is expecting
return device;
}
#endregion
}
static class Program
{
[STAThread]
private static void Main(string[] argv)
{
Interceptor icp = new Interceptor(10);
// do something with the Interceptor object
}
}
}
Hope that gets you on the right track.
Ok, I found an example code that was hidden on the GIT. Thank you google!
https://gist.github.com/1959219
It precises all function from DLL importation, with a working example.