如何在C＃中使用DLL函数而不添加DLL作为参考？

Question

I'm trying to use functions from a DLL that can't be added as Reference through Visual Studio (a message saying "reference cannot be added" appears). However, I've gotten instructions from the creator of the DLL and they suggested I use them like this in VB.Net:

Private Declare Function Prn_Init Lib "VAx_VPOS396_APPAPI.dll" () As Integer

That works, but now I want to write a program in C#. How do I "translate" that declaration to C#?

Additional: In C++ the declaration comes in a *.h file with these lines:

#ifndef  _VPOS396DLL_API_H
#define  _VPOS396DLL_API_H
VPOS396_DLL_API     int Prn_Init(void);

Answer 1

You should create the method(s) you want to use in C#, make them extern and add a [DllImport] attribute. For example:

[DllImport("kernel32.dll")]
static extern bool Beep(uint dwFreq, uint dwDuration);

See https://msdn.microsoft.com/en-us/library/aa984739%28v=vs.71%29.aspx

Answer 2

[System.Runtime.InteropServices.DllImport("VAx_VPOS396_APPAPI.dll")]

public static extern unsafe Int32 Prn_Init(void);

("unsafe" is optional)