c# - Xamarin 可移植类库中的简单获取请求(我需要它在 iOS 和 Windows Phone 上运行)

Question

我是 Xamarin 的新手，我正在尝试从 Internet 获取一个简单的文本文件。我将获取文本文件并将其解析为 xml。我可以使用一些示例来解析 xml，所以我认为如果我可以使用 http get 请求通过 Internet 获取文件内容就可以了。

我已经尝试了几个例子，而且我经常遇到部分工作的东西，但由于缺少方法定义或缺少程序集引用而无法工作。如果我可以克服错误(请参阅行注释)，这个示例有很大的希望:

我的进口

using System;

using Xamarin.Forms;
using System.Threading.Tasks;
using System.IO;
using System.Net;

我遇到问题的方法:

public static async Task<string> MakeGetRequest(string url, string cookie)
    {
        HttpWebRequest request = (HttpWebRequest)WebRequest.Create (url);
        request.ContentType = "text/html";
        request.Method = "GET";
        request.Headers ["Cookie"] = cookie;

        var response = await request.GetResponseAsync ();//Type 'System.Net.HttpWebRequest' does not contain a definition for 'GetResponseAsync'
        var respStream = response.GetResponseStream();
        respStream.Flush ();

        using (StreamReader sr = new StreamReader (respStream)) {
            //Need to return this response 
            string strContent = sr.ReadToEnd ();
            respStream = null;
            return strContent;
        }
    }

Answer 1

我在 Microsoft Page 上偶然发现了这个问题的答案

using System;

using Xamarin.Forms;
using System.Threading.Tasks;
using System.Net.Http;
using System.Diagnostics;

namespace pcl
{
    public class mainPage : ContentPage
    {
        public mainPage ()
        {

        var url = "http://ohiovr.com/church_files/dayspringWesleyan/mainscreen.xml";
        var myXMLstring = "";
        Task task = new Task (() =>{
            myXMLstring = AccessTheWebAsync (url).Result;
        });
        task.Start();
        task.Wait(); 
        Debug.WriteLine (myXMLstring);

        Content = new StackLayout { 
                Children = {
                    new Label { Text = "Hello StackOverflow" }
                }
            };
        }


        async Task<String> AccessTheWebAsync(String url)
        { 
            // You need to add a reference to System.Net.Http to declare client.
            HttpClient client = new HttpClient();

            // GetStringAsync returns a Task<string>. That means that when you await the 
            // task you'll get a string (urlContents).
            Task<string> getStringTask = client.GetStringAsync(url);

            // You can do work here that doesn't rely on the string from GetStringAsync.
            //DoIndependentWork();

            // The await operator suspends AccessTheWebAsync. 
            //  - AccessTheWebAsync can't continue until getStringTask is complete. 
            //  - Meanwhile, control returns to the caller of AccessTheWebAsync. 
            //  - Control resumes here when getStringTask is complete.  
            //  - The await operator then retrieves the string result from getStringTask. 
            string urlContents = await getStringTask;

            // The return statement specifies an integer result. 
            // Any methods that are awaiting AccessTheWebAsync retrieve the length value. 
            return urlContents;
        }


    }
}