我正在尝试编写一个可以从人口普查局的TIGER FTP站点下载shapefile的工具,该站点位于ftp://ftp2.census.gov/geo/tiger/TIGER2015/TRACT。我能够很好地列出文件,但是当我尝试下载文件时,我得到一个只是文件名的字符串,而不是文件内容本身。代码如下。
private static T FtpRequest<T, TReader>(string url, string method, Func<TReader, T> responseAction) where TReader : IDisposable {
var request = (FtpWebRequest)WebRequest.Create(url);
request.Method = WebRequestMethods.Ftp.ListDirectory;
request.Credentials = new NetworkCredential("anonymous", "anonymous");
request.UseBinary = true;
request.UsePassive = true;
var response = (FtpWebResponse)request.GetResponse();
using(var responseStream = response.GetResponseStream())
using(var reader = (TReader)Activator.CreateInstance(typeof(TReader), responseStream)) {
return responseAction(reader);
}
}
private static IList<string> ListDirectory(string url) {
return FtpRequest(url,
WebRequestMethods.Ftp.ListDirectory,
(StreamReader reader) => reader.ReadAllLines()
.Select(file => new Uri(new Uri(url), new Uri(file, UriKind.Relative)).AbsoluteUri)
.ToArray());
}
private static byte[] DownloadBinaryFile(string url) {
// NOTE: following code works in 4.6, but not 3.5
//using(var client = new WebClient()) {
// return client.DownloadData(url);
//}
// this code returns file name as string in both 4.6 and 3.5
return FtpRequest(url,
WebRequestMethods.Ftp.DownloadFile,
(BinaryReader reader) => {
using(var memoryStream = new MemoryStream()) {
var buffer = new byte[2048];
for(;;) {
var bytesRead = reader.Read(buffer, 0, buffer.Length);
if(bytesRead == 0)
break;
memoryStream.Write(buffer, 0, bytesRead);
}
memoryStream.Position = 0;
return memoryStream.GetBuffer();
}
});
}
internal static void Main(string[] args) {
var baseUrl = "ftp://ftp2.census.gov/geo/tiger/TIGER2015/TRACT";
foreach(var file in ListDirectory(baseUrl)) {
Console.WriteLine("Downloading: {0}", file);
var contents = DownloadBinaryFile(file);
using(var zipStream = new MemoryStream(contents))
using(var zipFile = ZipFile.Read(zipStream)) {
foreach(var entry in zipFile) {
Console.WriteLine(" -> {0}", entry.FileName);
//using(var entryReader = entry.OpenReader()) {
//}
}
}
}
Console.ReadKey();
}
如果我使用WebClient
,它会因.NET 3.5的错误而失败,但适用于.NET 4.6。相关代码已在上面注释掉。
人口普查网站有点挑剔,所以他们的网站完全有可能做出奇怪的事情。这就是我提供URL的原因,以防任何知识比我更多的人都能诊断出错误的服务器。
答案 0 :(得分:2)
在FtpRequest
方法中,您始终使用WebRequestMethods.Ftp.ListDirectory
方法,即使是下载也是如此。因此,您实际上“列出”了文件,这就是您在响应中获得其名称的原因。