将 C DLL 导入 C# 控制台应用程序时，如何编组结构参数 byRef？

Question

我将一个 C DLL 导入到我的 C# 程序中，并且必须编组一个 ByRef 结构参数。

这是 C 中函数的签名：

extern "C" {
int __stdcall FuncToImport(const char* stringToMarshall, StructFromDLL* structToMarshall);
...
...
...
}

这是我尝试在 C# 中导入它的方式

[DllImport("ImportedDll.dll", CallingConvention = CallingConvention.StdCall)]
public static extern IntPtr FuncToImport(string stringToImport, ref HandleRef structToImport);

在 Main 中调用它时出现异常： System.Runtime.InteropServices.MarshalDirectiveException: '"parameter #7" cannot be marshalled: HandleRefs cannot be marshalled as ByRef or not managed/managed Parameter..'

正确编组参数的可能方法是什么？

Answer 1

试试这个

[DllImport("ImportedDll.dll", CallingConvention = CallingConvention.StdCall)]
public static extern IntPtr FuncToImport(string stringToImport, IntPtr structToImport);

private static IntPtr StructToPointer<T>(T Struct) where T : struct
{
    //Allocates the necessary memoryspace and creates a pointer to this memory
    int rawsize = Marshal.SizeOf(Struct);
    IntPtr pointer = Marshal.AllocHGlobal(rawsize);

    //Writes the current data from the struct to the allocated memory
    Marshal.StructureToPtr(Struct, pointer, false);

    return pointer;
}

private static T PointerToStruct<T>(IntPtr pointer) where T : struct
{
    //Creates a Struct of the type of T from the pointed memory
    T Struct = Marshal.PtrToStructure<T>(pointer);
    //Frees the allocated memory
    Marshal.FreeHGlobal(pointer);
    return Struct;
}

IntPtr pointer = StructToPointer(structToImport);

FuncToImport("", pointer);

structToImport = PointerToStruct<Type of structToImport>(pointer);