using System;

using System.Runtime.InteropServices;

namespace Common

{

  public  class IECache

    {

        [DllImport("Wininet.dll", SetLastError = true, CharSet = CharSet.Auto)]

        public static extern Boolean GetUrlCacheEntryInfo(String lpxaUrlName, IntPtr lpCacheEntryInfo, ref int lpdwCacheEntryInfoBufferSize);

        const int ERROR_FILE_NOT_FOUND = 0x2;

        struct LPINTERNET_CACHE_ENTRY_INFO

        {

            public int dwStructSize;

            IntPtr lpszSourceUrlName;

            public IntPtr lpszLocalFileName;

            int CacheEntryType;

            int dwUseCount;

            int dwHitRate;

            int dwSizeLow;

            int dwSizeHigh;

            FILETIME LastModifiedTime;

            FILETIME Expiretime;

            FILETIME LastAccessTime;

            FILETIME LastSyncTime;

            IntPtr lpHeaderInfo;

            int dwheaderInfoSize;

            IntPtr lpszFileExtension;

            int dwEemptDelta;

        }

        // 返回 指定URL文件的缓存在本地文件系统中的路径

        public string GetPathForCachedFile(string fileUrl)

        {

            int cacheEntryInfoBufferSize = ;

            IntPtr cacheEntryInfoBuffer = IntPtr.Zero;

            int lastError; Boolean result;

            try

            {

                result = GetUrlCacheEntryInfo(fileUrl, IntPtr.Zero, ref cacheEntryInfoBufferSize);

                lastError = Marshal.GetLastWin32Error();

                if (result == false)

                {

                    if (lastError == ERROR_FILE_NOT_FOUND)

                        return null;

                }

                cacheEntryInfoBuffer = Marshal.AllocHGlobal(cacheEntryInfoBufferSize);

                result = GetUrlCacheEntryInfo(fileUrl, cacheEntryInfoBuffer, ref cacheEntryInfoBufferSize);

                lastError = Marshal.GetLastWin32Error();

                if (result == true)

                {

                    Object strObj = Marshal.PtrToStructure(cacheEntryInfoBuffer, typeof(LPINTERNET_CACHE_ENTRY_INFO));

                    LPINTERNET_CACHE_ENTRY_INFO internetCacheEntry = (LPINTERNET_CACHE_ENTRY_INFO)strObj;

                    String localFileName = Marshal.PtrToStringAuto(internetCacheEntry.lpszLocalFileName); return localFileName;

                }

                else

                    return null;// file not found

            }

            finally

            {

                if (!cacheEntryInfoBuffer.Equals(IntPtr.Zero))

                    Marshal.FreeHGlobal(cacheEntryInfoBuffer);

            }

        }

    }

}