Wininetdll函数库：根据url获取缓存文件

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;
namespace ConsoleApplication34
{
    class Program
    {
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
        public struct internet_cache_entry_info
        {
            public int dwstructsize;
            public IntPtr lpszsourceurlname;
            public IntPtr lpszlocalfilename;
            public int cacheentrytype;
            public int dwusecount;
            public int dwhitrate;
            public int dwsizelow;
            public int dwsizehigh;
            public FILETIME lastmodifiedtime;
            public FILETIME expiretime;
            public FILETIME lastaccesstime;
            public FILETIME lastsynctime;
            public IntPtr lpheaderinfo;
            public int dwheaderinfosize;
            public IntPtr lpszfileextension;
            public int dwexemptdelta;
        }
        [DllImport("wininet.dll", SetLastError = true, CharSet = CharSet.Auto)]
        public static extern IntPtr FindFirstUrlCacheEntry([MarshalAs(UnmanagedType.LPTStr)]   string urlsearchpattern, IntPtr lpfirstcacheentryinfo, ref   int lpdwfirstcacheentryinfobuffersize);
        [DllImport("wininet.dll", SetLastError = true, CharSet = CharSet.Auto)]
        public static extern bool GetUrlCacheEntryInfo([MarshalAs(UnmanagedType.LPTStr)]   string lpszurlname, IntPtr lpcacheentryinfo, ref   int lpdwcacheentryinfobuffersize);
        public static string getcatchfilename(string url)
        {
            int nneeded = 0, nbufsize = 0;
            IntPtr buf = IntPtr.Zero;
            FindFirstUrlCacheEntry(null, IntPtr.Zero, ref   nneeded);
            nbufsize = nneeded; buf = Marshal.AllocHGlobal(nbufsize);
            internet_cache_entry_info cacheitem;
            GetUrlCacheEntryInfo(url, buf, ref   nneeded);
            cacheitem = (internet_cache_entry_info)Marshal.PtrToStructure(buf, typeof(internet_cache_entry_info));
            string res = Marshal.PtrToStringAuto(cacheitem.lpszlocalfilename);
            return (res);
        }

        static void Main(string[] args)
        {
            string str = getcatchfilename("http://profile.csdn.net/jinjazz/picture/2.jpg");
            Console.WriteLine(str);
            Console.Read();
        }
    }
}