如何在 C++/CLI DLL 中从 C# 应用程序调用 function？

Question

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

Answer 1

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();
}

Answer 2

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 ();
    };
}

Answer 3

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();
        }
    }
}