從 URL 讀取到 .NET 中的字符串的最簡單方法

Question

給定一個字符串中的 URL：

http://www.example.com/test.xml

將文件內容從服務器（由 url 指向）下載到 C# 中的字符串中的最簡單/最簡潔的方法是什么？

我目前的做法是：

WebRequest request = WebRequest.Create("http://www.example.com/test.xml");
WebResponse response = request.GetResponse();
Stream dataStream = response.GetResponseStream();
StreamReader reader = new StreamReader(dataStream);
string responseFromServer = reader.ReadToEnd();

這是很多代碼，基本上可以是一行：

string responseFromServer = ????.GetStringFromUrl("http://www.example.com/test.xml");

注意：我不擔心異步調用——這不是生產代碼。

Answer 1

using(WebClient client = new WebClient()) {
   string s = client.DownloadString(url);
}

Answer 2

上述答案中的方法現在已棄用，目前推薦使用 HttpClient：

using (HttpClient client = new HttpClient())
{
    string s = await client.GetStringAsync(url);
}

Answer 3

鑒於在撰寫本文時， HttpClient是唯一剩余的、有效的 .Net 機制，用於執行此 function，並且在任何情況下您“不擔心異步調用” （這似乎是HttpClient不可避免的） ，我認為這個 function 應該讓你得到你所追求的：

public static class Http
{
    ///<remarks>NOTE: The <i>HttpCLient</i> class is <b>intended</b> to only ever be instantiated once in any application.</remarks>
    private static readonly HttpClient _client = new();

    /// <summary>Used to retrieve webserver data via simple <b>GET</b> requests.</summary>
    /// <param name="url">A string containing the complete web <b>URL</b> to submit.</param>
    /// <returns>Whatever <i>HttpClient</i> returns after attempting the supplied query (as a <i>Task&lt;string&gt;</i> value).</returns>
    /// <exception cref="InvalidOperationException">Returned if the supplied <i>url</i> string is null, empty or whitespace.</exception>
    private static async Task<string> HttpClientKludge( string url )
    {
        if ( string.IsNullOrWhiteSpace( url ) )
            throw new InvalidOperationException( "You must supply a url to interrogate for this function to work." );

        Uri uri;
        try { uri = new Uri( url ); }
        catch ( UriFormatException e ) { return $"{e.Message}\r\n{url}"; }

        return await _client.GetStringAsync( uri );
    }

    /// <summary>Attempts to interrogate a website via the supplied URL and stores the result in a <i>string</i>.</summary>
    /// <param name="url">A string containing a fully-formed, proper URL to retrieve.</param>
    /// <param name="captureExceptions">If <b>TRUE</b>, any Exceptions generated by the operation will be suppressed with their Message returned as the result string, otherwise they're thrown normally.</param>
    /// <returns>The result generated by submitting the request, as a <i>string</i>.</returns>
    public static string Get( string url, bool captureExceptions = true )
    {
        string result;
        try { result = HttpClientKludge( url ).Result; }
        catch (AggregateException e)
        {
            if (!captureExceptions) throw;
            result = e.InnerException is null ? e.Message : e.InnerException.Message;
        }
        return result;
    }
}

有了這個，任何時候你想用一個簡單的 URL+GET 查詢來詢問一個網站，你可以簡單地做：

string query = "/search?q=Easiest+way+to+read+from+a+URL+into+a+string+in+.NET",
siteResponse = Http.Get( $"https://www.google.com{query}" );
// Now use 'siteResponse' in any way you want...