托管和非托管类型交互的问题

 

这是非托管代码封装的结构体:  typedef struct structural_MEDIA_MOTION_INFO          {                                                        DWORD dwEnable;          DWORD dwRangeCount;          DWORD dwRange[3][4];          DWORD dwSensitive[3];          } MEDIA_MOTION_INFO;    这是非托管代码中的函数原型： void KGetMotionInfo(HANDLE h, MEDIA_MOTION_INFO* MotionInfo) 做法一：  把非托管结构体封装成托管结构体 [StructLayout(LayoutKind.Sequential, Pack=1)]         public struct MediaMotionInfo         {             public Int32 dwEnable;             public Int32 dwRangeCount;             [MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)] public int[] dwRange;             [MarshalAs(UnmanagedType.ByValArray,SizeConst = 3)] public int[] dwSensitive;         }   因为非托管代码要求地址传递（MEDIA_MOTION_INFO*），所以本处用（ref MediaMotionInfo） /// <summary>         /// Get the Server’s Motion setting value.         /// </summary>         /// <param name="h">[in] The handle returned by KOpenInterface()</param>        /// <param name="MotionInfo">[out] the Motion information on the video server.</param>         [DllImport(DLLFILE, EntryPoint = "KGetMotionInfo")]         public static extern void GetMotionInfo(IntPtr h,ref MediaMotionInfo MotionInfo);   调用结果正确 mmi属性是[out]，所以可以得到正确的结果结构体。 private void getMotionButton_Click(object sender, EventArgs e)         {                 mmi = new Acti10000Sdk.MediaMotionInfo();                 Acti10000Sdk.GetMotionInfo(h, ref mmi);             }         } 此图反映值类型托管和非托管之间的引用传递： 解决方法二： 我把非托管的结构体封装成一个类，结构如下： [StructLayout(LayoutKind.Sequential, Pack = 1)] public class MediaMotionInfo {     public Int32 dwEnable;     public Int32 dwRangeCount;     [MarshalAs(UnmanagedType.ByValArray, SizeConst = 12)]     public int[] dwRange=new int[12];     [MarshalAs(UnmanagedType.ByValArray, SizeConst = 3)]     public int[] dwSensitive=new int[3]; }   由于我封装的是个类，所以直接写MediaMotionInfo就是引用类型，我认为此处和非托管代码也是匹配的。 /// <summary>         /// Get the Server’s Motion setting value.         /// </summary>         /// <param name="h">[in] The handle returned by KOpenInterface()</param>         /// <param name="MotionInfo">[out] the Motion information on the video server.</param>         [DllImport(DLLFILE, EntryPoint = "KGetMotionInfo")]         public static extern void GetMotionInfo(IntPtr h,  MediaMotionInfo MotionInfo);   此处参数为一个类的引用，指向堆的上的对象。问题是这样做为什么得不到返回的类呢？ private void getMotionButton_Click(object sender, EventArgs e)         {                 mmi = new Acti10000Sdk.MediaMotionInfo();                 Acti10000Sdk.GetMotionInfo(h, mmi);             }         }  此图反映引用类型在托管和非托管的值传递：   问题：第二种方法哪里错了。

转载于:https://www.cnblogs.com/blue-th/archive/2008/09/25/1298940.html