有时候为了多个进程之间共享数据，共享内存是我首先想到的东西。但也遇到了很多问题，以下是我对共享内存在asp.net中使用的一些问题的总结。
共享内存的基础操作类
public class ShareMem { [DllImport("user32.dll", CharSet = CharSet.Auto)] public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, int wParam, IntPtr lParam); [DllImport("Kernel32.dll", CharSet = CharSet.Auto)] public static extern IntPtr CreateFileMapping(int hFile, IntPtr lpAttributes, uint flProtect, uint dwMaxSizeHi, uint dwMaxSizeLow, string lpName); [DllImport("Kernel32.dll", CharSet = CharSet.Auto)] public static extern IntPtr OpenFileMapping(int dwDesiredAccess, [MarshalAs(UnmanagedType.Bool)] bool bInheritHandle, string lpName); [DllImport("Kernel32.dll", CharSet = CharSet.Auto)] public static extern IntPtr MapViewOfFile(IntPtr hFileMapping, uint dwDesiredAccess, uint dwFileOffsetHigh, uint dwFileOffsetLow, uint dwNumberOfBytesToMap); [DllImport("Kernel32.dll", CharSet = CharSet.Auto)] public static extern bool UnmapViewOfFile(IntPtr pvBaseAddress); [DllImport("Kernel32.dll", CharSet = CharSet.Auto)] public static extern bool CloseHandle(IntPtr handle); [DllImport("kernel32", EntryPoint = "GetLastError")] public static extern int GetLastError(); const int ERROR_ALREADY_EXISTS = 183; const int FILE_MAP_COPY = 0x0001; const int FILE_MAP_WRITE = 0x0002; const int FILE_MAP_READ = 0x0004; const int FILE_MAP_ALL_ACCESS = 0x0002 | 0x0004; const int PAGE_READONLY = 0x02; const int PAGE_READWRITE = 0x04; const int PAGE_WRITECOPY = 0x08; const int PAGE_EXECUTE = 0x10; const int PAGE_EXECUTE_READ = 0x20; const int PAGE_EXECUTE_READWRITE = 0x40; const int SEC_COMMIT = 0x8000000; const int SEC_IMAGE = 0x1000000; const int SEC_NOCACHE = 0x10000000; const int SEC_RESERVE = 0x4000000; const int INVALID_HANDLE_VALUE = -1; IntPtr m_hSharedMemoryFile = IntPtr.Zero; IntPtr m_pwData = IntPtr.Zero; bool m_bAlreadyExist = false; bool m_bInit = false; long m_MemSize = 0; public ShareMem() { } ~ShareMem() { Close(); } /// <summary> /// 初始化共享内存 /// </summary> /// <param name="strName">共享内存名称</param> /// <param name="lngSize">共享内存大小</param> /// <returns></returns> public int Init(string strName, long lngSize) { if (lngSize <= 0 || lngSize > 0x00800000) lngSize = 0x00800000; m_MemSize = lngSize; SecurityStruct ss = new SecurityStruct(); if (strName.Length > 0) { //创建内存共享体(INVALID_HANDLE_VALUE) m_hSharedMemoryFile = CreateFileMapping(INVALID_HANDLE_VALUE, ss.AnonymousSA(true), (uint)PAGE_READWRITE, 0, (uint)lngSize, strName); if (m_hSharedMemoryFile == IntPtr.Zero) { m_bAlreadyExist = false; m_bInit = false; return 2; //创建共享体失败 } else { if (GetLastError() == ERROR_ALREADY_EXISTS) //已经创建 { m_bAlreadyExist = true; } else //新创建 { m_bAlreadyExist = false; } } //--------------------------------------- //创建内存映射 m_pwData = MapViewOfFile(m_hSharedMemoryFile, FILE_MAP_WRITE, 0, 0, (uint)lngSize); if (m_pwData == IntPtr.Zero) { m_bInit = false; CloseHandle(m_hSharedMemoryFile); return 3; //创建内存映射失败 } else { m_bInit = true; if (m_bAlreadyExist == false) { //初始化 } } //---------------------------------------- } else { return 1; //参数错误 } return 0; //创建成功 } private IntPtr AnonymousSA() { throw new NotImplementedException(); } /// <summary> /// 关闭共享内存 /// </summary> public void Close() { if (m_bInit) { UnmapViewOfFile(m_pwData); CloseHandle(m_hSharedMemoryFile); } } /// <summary> /// 读数据 /// </summary> /// <param name="bytData">数据</param> /// <param name="lngAddr">起始地址</param> /// <param name="lngSize">个数</param> /// <returns></returns> public int Read(ref byte[] bytData, int lngAddr, int lngSize) { if (lngAddr + lngSize > m_MemSize) return 2; //超出数据区 if (m_bInit) { Marshal.Copy(m_pwData, bytData, lngAddr, lngSize); } else { return 1; //共享内存未初始化 } return 0; //读成功 } /// <summary> /// 写数据 /// </summary> /// <param name="bytData">数据</param> /// <param name="lngAddr">起始地址</param> /// <param name="lngSize">个数</param> /// <returns></returns> public int Write(byte[] bytData, int lngAddr, int lngSize) { if (lngAddr + lngSize > m_MemSize) return 2; //超出数据区 if (m_bInit) { Marshal.Copy(bytData, lngAddr, m_pwData, lngSize); } else { return 1; //共享内存未初始化 } return 0; //写成功 } }
上面这个基础类是从某处转来的，具体出处已遗忘～如谁知道可以提醒我下。
通过上面的基础类，利用winform打造一段内存数据，用于不同进程中共享数据。但在asp.net中，网页中去访问这段共享内存，返回却是无法访问。仔细查了下，发现是权限问题。网页访问者的权限过低无法访问winform打造的内存数据。网上有很多解决方法，比如添加安全描述等，不一一列举。我此处采用的是最简单的方案，建立共享内存的时候，名称采用Global//贡献内存名，Global//代表了这段内存在本机范围内共享，无视权限高低。这样做较简单，但也会带来一定的安全方面的副作用，以待将来完善。
