用WebBrowser下載檔案

建立一個新的WebBrowser元件，繼承自WebBrowser

內部包含URLDownloadToFile這個windows的API

程式碼如下

1. public class WebBrowserWithDownloadAbility : WebBrowser
2. {
3. /// <summary>
4. /// The URLMON library contains this function, URLDownloadToFile, which is a way
5. /// to download files without user prompts. The ExecWB( _SAVEAS ) function always
6. /// prompts the user, even if _DONTPROMPTUSER parameter is specified, for "internet
7. /// security reasons". This function gets around those reasons.
8. /// </summary>
9. /// <param name="callerPointer">Pointer to caller object (AX).</param>
10. /// <param name="url">String of the URL.</param>
11. /// <param name="filePathWithName">String of the destination filename/path.</param>
12. /// <param name="reserved">[reserved].</param>
13. /// <param name="callBack">A callback function to monitor progress or abort.</param>
14. /// <returns>0 for okay.</returns>
15. [DllImport("urlmon.dll", CharSet = CharSet.Auto, SetLastError = true)]
16. static extern Int32 URLDownloadToFile(
17. [MarshalAs(UnmanagedType.IUnknown)] object callerPointer,
18. [MarshalAs(UnmanagedType.LPWStr)] string url,
19. [MarshalAs(UnmanagedType.LPWStr)] string filePathWithName,
20. Int32 reserved,
21. IntPtr callBack);
23. /// <summary>
24. /// Download a file from the webpage and save it to the destination without promting the user
25. /// </summary>
26. /// <param name="url">the url with the file</param>
27. /// <param name="destinationFullPathWithName">the absolut full path with the filename as destination</param>
28. /// <returns></returns>
29. public FileInfo DownloadFile(string url, string destinationFullPathWithName)
30. {
31. URLDownloadToFile(null, url, destinationFullPathWithName, 0, IntPtr.Zero);
32. return new FileInfo(destinationFullPathWithName);
33. }
34. }

如果你的網址中有中文字

則需要呼叫這段程式碼進行編碼轉換，否則會出現錯誤(無法下載)

1. static string ChEncodeUrl(string str)
2. {
3. byte[] byt = Encoding.Default.GetBytes(str);
4. string ret = HttpUtility.UrlEncode(str, Encoding.UTF8);
5. return ret;
6. }

用了以後你可能會發現有點問題，他下載的檔案有時怎麼都不會變

原來是因為他會先去暫存裡找資料，如果找到了，就不進行下載

因此，如果要確保資料是最新的

需要清除舊的資料

使用的程式碼如下

1. [DllImport(@"wininet",
2. SetLastError = true,
3. CharSet = CharSet.Auto,
4. EntryPoint = "DeleteUrlCacheEntryA",
5. CallingConvention = CallingConvention.StdCall)]
6. public static extern bool DeleteUrlCacheEntry(string lpszUrlName);

使用時，呼叫這段程式碼清除暫存

1. DeleteUrlCacheEntry("www.google.com");