如何从互联网读取文件？

Question

简单的问题： 我有一个在线文件（txt）。如何读取它并检查它是否存在？ (C#.net 2.0)

Answer 1

2024 年更新

WebClient

已贬值，有利于使用

HTTPClient

。

HttpClient client = new HttpClient();
HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, "http://yoururl/test.txt");
HttpResponseMessage response = client.Send(request);
StreamReader reader = new StreamReader(response.Content.ReadAsStream());
string content = reader.ReadToEnd();

原答案

WebClient 类适用于：  

WebClient client = new WebClient();
Stream stream = client.OpenRead("http://yoururl/test.txt");
StreamReader reader = new StreamReader(stream);
String content = reader.ReadToEnd();

Answer 2

来自 http://www.csharp-station.com/HowTo/HttpWebFetch.aspx

    HttpWebRequest  request  = (HttpWebRequest)
        WebRequest.Create("myurl");

        // execute the request
        HttpWebResponse response = (HttpWebResponse)
            request.GetResponse();
            // we will read data via the response stream
        Stream resStream = response.GetResponseStream();
    string tempString = null;
    int    count      = 0;

    do
    {
        // fill the buffer with data
        count = resStream.Read(buf, 0, buf.Length);

        // make sure we read some data
        if (count != 0)
        {
            // translate from bytes to ASCII text
            tempString = Encoding.ASCII.GetString(buf, 0, count);

            // continue building the string
            sb.Append(tempString);
        }
    }
    while (count > 0); // any more data to read?

    // print out page source
    Console.WriteLine(sb.ToString());

Answer 3

更简单一点的方法：

string fileContent = new WebClient().DownloadString("yourURL");

Answer 4

首先，您可以下载二进制文件：

public byte[] GetFileViaHttp(string url)
{
    using (WebClient client = new WebClient())
    {
        return client.DownloadData(url);
    }
}

然后你可以为文本文件创建字符串数组（假设UTF-8并且它是一个文本文件）：

var result = GetFileViaHttp(@"http://example.com/index.html");
string str = Encoding.UTF8.GetString(result);
string[] strArr = str.Split(new[] { "\r\n" }, StringSplitOptions.RemoveEmptyEntries);

您将收到每个数组字段中的每一行（空）文本。

Answer 5

HttpWebRequest

的替代方案是

WebClient

    // create a new instance of WebClient
    WebClient client = new WebClient();

    // set the user agent to IE6
    client.Headers.Add("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705;)");
    try
    {
        // actually execute the GET request
        string ret = client.DownloadString("http://www.google.com/");

        // ret now contains the contents of the webpage
        Console.WriteLine("First 256 bytes of response: " + ret.Substring(0,265));
    }
    catch (WebException we)
    {
        // WebException.Status holds useful information
        Console.WriteLine(we.Message + "\n" + we.Status.ToString());
    }
    catch (NotSupportedException ne)
    {
        // other errors
        Console.WriteLine(ne.Message);
    }

示例来自 http://www.daveamenta.com/2008-05/c-webclient-usage/

Answer 6

这太容易了：

using System.Net;
using System.IO;

...

    using (WebClient client = new WebClient()) {
        //... client.options
        Stream stream = client.OpenRead("http://.........");
        using (StreamReader reader = new StreamReader(stream)) {
            string content = reader.ReadToEnd();
        }
    }

“WebClient”和“StreamReader”是一次性的。文件的内容将进入“content”变量。

客户端变量包含多个配置选项。

默认配置可以称为：

string content = new WebClient().DownloadString("http://.........");

Answer 7

看看

System.Net.WebClient

，文档甚至有一个检索文件的示例。

但是测试文件是否存在意味着请求该文件并捕获异常（如果不存在）。