473,854 Members | 1,449 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

use DLL with c# DllImport

2 New Member
Hej,

I want to use a DLL (1394camera.dll ) (written in c++, I presume) in my c# project. The Dll contains functions in various classes, e.g. 'C1394Camera::C heckLink', according to the docs defined as follows:

int
CheckLink(
);
Trying to invoke the function in c# as:

Expand|Select|Wrap|Line Numbers
  1. public class Kamera
  2.     {
  3.         [DllImport("1394camera.dll")]
  4.         private static extern int CheckLink();
  5.         public int Anzahl;
  6.         public Kamera()
  7.         {
  8.             Anzahl = CheckLink();
  9.         }
  10.     }
doesn't work, neither does

Expand|Select|Wrap|Line Numbers
  1.    public class Kamera
  2.     {
  3.         [DllImport("1394camera.dll", EntryPoint = "C1394Camera::CheckLink")]
  4.         private static extern int CheckLink();
  5.         public int Anzahl;
  6.         public Kamera()
  7.         {
  8.             Anzahl = CheckLink();
  9.         }
  10.     }
I always get an "Unable to find an entry point named 'C1394Camera::C heckLink' in DLL '1394camera.dll '."

How can I correctly address the functions in this dll?

Thank you in advance, Franz
Mar 20 '06 #1
6 77692
fhennies
2 New Member
Hej Folks,

problem (at least this) solved. Using depends.exe exe I figured the right entry point out. This code now works (accesses the DLL-function, at least):

Expand|Select|Wrap|Line Numbers
  1.    public class Kamera
  2.     {
  3.         [DllImport("1394camera.dll", EntryPoint = "?CheckLink@C1394Camera@@QAEHXZ")]
  4.         private static extern int CheckLink();
  5.         public int Anzahl;
  6.         public Kamera()
  7.         {
  8.             Anzahl = CheckLink();
  9.         }
  10.     }
Now I get access violations and SecurityExcepti ons...
Mar 21 '06 #2
ccsuser
2 New Member
Hej Folks,

problem (at least this) solved. Using depends.exe exe I figured the right entry point out. This code now works (accesses the DLL-function, at least):

Expand|Select|Wrap|Line Numbers
  1.    public class Kamera
  2.     {
  3.         [DllImport("1394camera.dll", EntryPoint = "?CheckLink@C1394Camera@@QAEHXZ")]
  4.         private static extern int CheckLink();
  5.         public int Anzahl;
  6.         public Kamera()
  7.         {
  8.             Anzahl = CheckLink();
  9.         }
  10.     }
Now I get access violations and SecurityExcepti ons...
Does this work? [DllImport("1394 camera.dll", EntryPoint = "?CheckLink@C13 94Camera@@QAEHX Z")]
Sep 13 '06 #3
ccsuser
2 New Member
Solution found: He use command "dumpbin/exports" in Visual Studio Command Prompt to see it.
Sep 13 '06 #4
eilarafi
1 New Member
Hello

i am new in c# and would like to use exported classes from c++ dll.
i have more then one method that i would like to use from my exported c++ class, does it mean that i need to declare more then one entry point? i tried that in a c# class and it did not work (error message:dllimpo rt multiple attriutes)
how can i do that? how does the c# instantiate the object.

thanks,
Eila
Oct 5 '07 #5
tihomirtiankov
1 New Member
Hi
I have also the same problem. I wrote this code.
Expand|Select|Wrap|Line Numbers
  1. class Kamera1
  2.     {
  3.  
  4.         [DllImport("1394camera.dll", EntryPoint = "?InitCamera@C1394Camera@@QAEHXZ")]
  5.  
  6.  
  7.         public static extern void InitCamera();
  8.         //public int Anzahl, Anzahl1;
  9.  
  10.         public void Kamera2()
  11.         {                        
  12.               InitCamera();
  13.  
  14.         }
  15.  
  16.     }
  17.     class Kamera2
  18.     {
  19.  
  20.         [DllImport("1394camera.dll", EntryPoint = "?GetMaxSpeed@C1394Camera@@QAEHXZ")]
  21.  
  22.  
  23.         public static extern int GetMaxSpeed();
  24.         public int Anzahl2;
  25.  
  26.         public void Kamera3()
  27.         {
  28.             Anzahl2 = GetMaxSpeed();
  29.  
  30.         }
  31.  
  32.     }

Into the button event I wrote this code:

Expand|Select|Wrap|Line Numbers
  1.  private void button1_Click(object sender, EventArgs e)
  2.         {
  3.  
  4.  
  5.             k.Anzahl.ToString();
  6.  
  7.             textBox1.Text = k.Anzahl.ToString();
  8.  
  9.             k1.Kamera2();
  10.        }
I received as a result "0" when the camera is connected or not. I think that there is a problem. Could you help me to start acquire image in C#.
Thank's a lot
Oct 31 '08 #6
magicmike
2 New Member
Just curious but is there a particular reason you are choosing to include the assembly in your project using DllImport? You could just include it as a referenced assembly and include the namespace declaration in the "using" directives of the .cs files you wish to use it in. The fact it is in c++ makes no difference to the runtime compiler as long as the assembly is pre-compiled. The runtime only reads the IL code generated from an assembly, not the actual assembly itself and it doesn't care (or even know) what particular .NET language the assembly was written in when reading IL code.

Just curious
Mar 27 '12 #7

Sign in to post your reply or Sign up for a free account.

Similar topics

15
4471
by: Jim | last post by:
I am extremely frustrated. I am building c# application for a call center and am using a third party API to access some hardware. When develop and test my class using the windows console the application runs flawlessly, but once I call the class from inside a c# windows application the program freezes, crashes etc... there must be a way to make this work inside a windows app as it run great as a command line app.
6
5915
by: Tim Mulholland | last post by:
Whats the correct C# datatype (or marshalling function or something) to use when you're importing a function that has a signature similar to char* FuncA(char c) ? Assuming you know that both the parameter for the function and the return value are c-style strings?
9
4978
by: Ole Christensen | last post by:
I'm trying to make a sort of conditional compilation in my C# code because my app is intended to run on both a Pocket PC and on a normal desktop PC. My code uses a call to an API function that on the PPC is located in coredll.dll and on the desktop in kernel32.dll. I could make two versions of the DllImported funktions but then I would have to ask for the OS version in every call to the function. This however causes the code to look messy...
3
3465
by: Mark Jerde | last post by:
I'm sill learning VS .NET 2003, not an expert yet. I'm calling an unmanaged C++ DLL from C# using . When the whole project is done I will be calling a total of 5 C++ DLLs from C#. All the DLLs have the same signature, and I never have to call more than one DLL in the same program. (The DLLs parse and validate 5 different binary formats.) Originally I was expecting to have 5 different C# programs as the constants are different for each...
1
1730
by: Brian Anderson | last post by:
Hello, I have a native, C++ console app that uses ~26MB of RAM when it runs. It uses quite a lot of RAM to make some math but will never xceed 26MB. Now I've made a dll out of this code and use it with DllImport in a C# console application. Basically I just access main() and pass my parameters. w00t! RAM used by the C# app is now 228 MB !
2
10486
by: Brian Anderson | last post by:
Hello, is it possible to use DllImport to call a DLL in ASP.NET ? Or is it necessarry that my DLL has to be copied into \System32 ? My DLL is a native C++ 7.1 DLL (not managed, no COM, no regsvr32) and uses Assembler to make some math in SSE. The result is given out as an Int. Using a C# console app (code below) it work fine & fast.
2
3675
by: Ed | last post by:
Hello, dear all, I often see these two import usage in the code. Both are the interface to use the Dll library. I think they are the same. Normally P/Invoke means using the to import the dll. But I have some confusion about them. 1. Is the "_declspec(dllimport)" also one of the forms of P/Invoke? 2. From performance aspect, which way is more better? 3. What's the difference of them.
1
4285
by: kardon33 | last post by:
Let me explain my problem, Im currently trying to use a Perl module that was built for a Windows OS that uses a .dll and .lib file. I have obtained the c header files that the modules were built with. I am trying to use SWIG to write my Perl mod with those files but I getting a bunch of errors with the "extern "C" __declspec(dllimport)" command kinda know that basics of the command, its used to declare vars from a .dll. If im wrong please...
9
8217
by: jjones7947 | last post by:
Am doing a JNI wrap on a C++ API, am using VC7 and Eclipse. In preparation, I created a C++ executable which mimicked the flow of the JNI, i.e. a driver file which called methods in file with methods which call the API functions I want to use. That compiled and ran well. The C++ code is as follows: My header file void createSummarizer(char* rdir, char* lFile, char* key); void createInputOptions(const char* genre, const char* variant, const...
1
5807
by: elke | last post by:
Hi, I want to use an unmanaged dll in C# .net and I'm having some troubles witch a function that should return an array. I'm new at this, so I don't know what I'm doing wrong. Here is some code: #define USERINT_FUNC __cdecl #ifdef __cplusplus extern "C" { #endif
0
9901
marktang
by: marktang | last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look ! Part I. Meaning of...
0
11031
Oralloy
by: Oralloy | last post by:
Hello folks, I am unable to find appropriate documentation on the type promotion of bit-fields when using the generalised comparison operator "<=>". The problem is that using the GNU compilers, it seems that the internal comparison operator "<=>" tries to promote arguments from unsigned to signed. This is as boiled down as I can make it. Here is my compilation command: g++-12 -std=c++20 -Wnarrowing bit_field.cpp Here is the code in...
0
10685
jinu1996
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth. The Art of Business Website Design Your website is...
1
7918
isladogs
by: isladogs | last post by:
The next Access Europe User Group meeting will be on Wednesday 1 May 2024 starting at 18:00 UK time (6PM UTC+1) and finishing by 19:30 (7.30PM). In this session, we are pleased to welcome a new presenter, Adolph Dupré who will be discussing some powerful techniques for using class modules. He will explain when you may want to use classes instead of User Defined Types (UDT). For example, to manage the data in unbound forms. Adolph will...
0
5750
by: TSSRALBI | last post by:
Hello I'm a network technician in training and I need your help. I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs. The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols. I succeeded, with both firewalls in the same network. But I'm wondering if it's possible to do the same thing, with 2 Pfsense firewalls...
0
5942
by: adsilva | last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
1
4563
by: 6302768590 | last post by:
Hai team i want code for transfer the data from one system to another through IP address by using C# our system has to for every 5mins then we have to update the data what the data is updated we have to send another system
2
4162
muto222
by: muto222 | last post by:
How can i add a mobile payment intergratation into php mysql website.
3
3188
bsmnconsultancy
by: bsmnconsultancy | last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.