将包含数组的C结构编组到C# [英] Marshalling C struct containing arrays to C#

问题描述

在 stackoverflow 社区的大力帮助下，我设法调用了本机DLL函数.但是，我不能修改 ID或intersects数组的值.不管我在DLL方面使用它是什么，旧值仍然存在.似乎是只读的.

With great help of the stackoverflow community, I've managed to call a native DLL function. However, I can't modify the values of ID or intersects array. No matter what I do with it on the DLL side, the old value remains. It seems read-only.

以下是一些代码片段:

C ++结构:

typedef struct _Face {
    int ID;
    int intersects[625];
} Face;

C#映射:

[StructLayout(LayoutKind.Sequential)]
    public struct Face {
        public int ID;

        [MarshalAs(UnmanagedType.ByValArray, SizeConst = 625)]
        public int[] intersects;
    }

C ++方法(在VS2010中类型设置为DLL):

C++ method (type set to DLL in VS2010):

extern "C" int __declspec(dllexport) __stdcall 
solve(Face *faces, int n){
for(int i =0; i<n; i++){
    for(int r=0; r<625; r++){
        faces[i].intersects[r] = 333;
        faces[i].ID = 666;
        }
    }

C#方法签名:

[DllImport("lib.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.StdCall)]
public static extern int solve(Face[] faces, int len);

C#方法调用:

Face[] faces = new Face[10];
faces[0].intersects = new int[625];
faces[0].ID = -1; //.. and add 9 more ..

solve(faces, faces.Length);

// faces[0].ID still equals -1 and not 666

最诚挚的问候， e.

推荐答案

您必须明确告诉pinvoke编组说需要将数组编组回去.您可以使用[In]和[Out]属性来执行此操作.像这样:

You have to tell the pinvoke marshaller explicitly that the array needs to be marshaled back. You do this with the [In] and [Out] attributes. Like this:

    [DllImport("...")]
    public static extern int solve([In, Out] Face[] faces, int len);

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