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Posted 4 Jan 2005


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Dynamic Invoke from Unmanaged DLL

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3.44/5 (9 votes)
4 Jan 2005
This article explains invoking unmanaged DLL functions from C#.


This article demonstrates how to call an unmanaged MFC DLL function from a C# code. Code uses Reflection namespace. To use code snippets below, you must add the following:

using System.Reflection.Emit;
using System.Reflection;

Imagine you have an MFC DLL (getmyversion.dll) with function named int GetDllversion(char* verstr) which returns your DLL's version in verstr.

The below function creates a dynamic assembly object. And DefinePInvokeMethod method creates a method which we will use to access our DLL function. To complete our global ops for our dynamic module, call CreateGlobalFunctions. Using GetMethod function of our previously created method, we can invoke our MFC DLL function.

public  object DynamicDllFunctionInvoke( string DllPath, string EntryPoint ) 
   // Version string definition
   byte[] verstr = new byte[1024];
   //Define return type of your dll function.
   Type returnType = typeof(int);        
   //out or in parameters of your function.   
   Type [] parameterTypes = {typeof(byte[])};
   object[] parameterValues = {verstr};
   string entryPoint = entrypoint;
   // Create a dynamic assembly and a dynamic module
   AssemblyName asmName = new AssemblyName();
   asmName.Name = "tempDll";
   AssemblyBuilder dynamicAsm = 
   ModuleBuilder dynamicMod = 

   // Dynamically construct a global PInvoke signature 
   // using the input information
   MethodBuilder dynamicMethod = dynamicMod.DefinePInvokeMethod(
     entryPoint, DllPath, MethodAttributes.Static | MethodAttributes.Public
     | MethodAttributes.PinvokeImpl , CallingConventions.Standard,
     returnType, parameterTypes, CallingConvention.Winapi, 

   // This global method is now complete

   // Get a MethodInfo for the PInvoke method
   MethodInfo mi = dynamicMod.GetMethod(EntryPoint);
   // Invoke the static method and return whatever it returns
   object retval = mi.Invoke(null, parameterValues);
   // Filled verstr paramter.
   return retval;

Sample calling of the method is as below:



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Comments and Discussions

GeneralMy vote of 1 Pin
merikin28-Jun-10 4:14
Membermerikin28-Jun-10 4:14 
Questionreal dynamic invoke Pin
fredarmoni21-Aug-07 0:10
Memberfredarmoni21-Aug-07 0:10 
AnswerRe: real dynamic inoke Pin
Shawn-USA5-Aug-13 15:21
MemberShawn-USA5-Aug-13 15:21 
QuestionHow to Unload a DLL Pin
Ronakkumar Patel31-May-07 13:21
MemberRonakkumar Patel31-May-07 13:21 
AnswerRe: How to Unload a DLL Pin
Shawn-USA5-Aug-13 15:24
MemberShawn-USA5-Aug-13 15:24 
Questionwhen load dll of vc++6.0 its generated error?? Pin
keyur_patel26-Mar-07 21:57
Memberkeyur_patel26-Mar-07 21:57 
AnswerRe: when load dll of vc++6.0 its generated error?? Pin
calaquendi26-Mar-07 22:34
Membercalaquendi26-Mar-07 22:34 
QuestionReturned value does not work Pin
Michal Czardybon31-May-06 0:10
MemberMichal Czardybon31-May-06 0:10 
Generalref string Pin
John Orosz17-Mar-05 6:34
MemberJohn Orosz17-Mar-05 6:34 
QuestionRe: ref string Pin
npat19-Jan-07 11:11
Membernpat19-Jan-07 11:11 
AnswerRe: ref string Pin
Jorge Branco29-Aug-08 10:28
MemberJorge Branco29-Aug-08 10:28 
GeneralRe: ref string Pin
Jorge Branco29-Aug-08 10:39
MemberJorge Branco29-Aug-08 10:39 
QuestionDllImport Attribute? Pin
Marc Clifton4-Jan-05 5:25
mvaMarc Clifton4-Jan-05 5:25 
AnswerRe: DllImport Attribute? Pin
Chris Richardson4-Jan-05 10:40
MemberChris Richardson4-Jan-05 10:40 
GeneralRe: DllImport Attribute? Pin
Marc Clifton4-Jan-05 10:56
mvaMarc Clifton4-Jan-05 10:56 
GeneralRe: DllImport Attribute? Pin
Chris Richardson4-Jan-05 11:06
MemberChris Richardson4-Jan-05 11:06 
AnswerRe: DllImport Attribute? Pin
calaquendi4-Jan-05 20:09
Membercalaquendi4-Jan-05 20:09 
AnswerRe: DllImport Attribute? Pin
Leonardo Pessoa5-Jan-05 0:20
MemberLeonardo Pessoa5-Jan-05 0:20 
GeneralRe: DllImport Attribute? Pin
Superfan25-Jan-05 15:01
MemberSuperfan25-Jan-05 15:01 
GeneralRe: DllImport Attribute? Pin
Leonardo Pessoa25-Jan-05 23:23
MemberLeonardo Pessoa25-Jan-05 23:23 
GeneralRe: DllImport Attribute? Pin
Superfan26-Jan-05 5:34
MemberSuperfan26-Jan-05 5:34 

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