不知道用什麼詞形容，就叫它假非同步吧。

寫非同步方法，async 和 await 要一路寫到底，否則就是假非同步，並不能提高請求執行緒池的吞吐量。

/// <summary>
/// HttpGet
/// </summary>
/// <param name="url">
 
url路徑名稱</param>
/// <param name="cookie">cookie</param>
public static string HttpGet(string url, CookieContainer cookie = null, WebHeaderCollection headers = null)
{
    try
    {
        // 設定引數
        HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
        request.CookieContainer 
 
= cookie;
        request.Method = "GET";
        request.ContentType = "text/plain;charset=utf-8";

        if (headers != null)
        {
            foreach (string key in headers.Keys)
            {
                request.Headers.Add(key, headers[key]);
            }
        }

        //傳送請求並獲取相應迴應資料
 

        HttpWebResponse response = request.GetResponse() as HttpWebResponse;
        //直到request.GetResponse()程式才開始向目標網頁傳送Post請求
        Stream instream = response.GetResponseStream();
        StreamReader sr = new StreamReader(instream, Encoding.UTF8);
        //返回結果網頁（html）程式碼
        string content = sr.ReadToEnd();
        return content;
    }
    catch (Exception ex)
    {
        LogUtil.Error(ex);
        return string.Empty;
    }
}

HttpUtil.HttpGetAsync方法：

/// <summary>
/// HttpGetAsync
/// </summary>
/// <param name="url">url路徑名稱</param>
/// <param name="cookie">cookie</param>
public static async Task<string> HttpGetAsync(string url, CookieContainer cookie = null, WebHeaderCollection headers = null)
{
    try
    {
        // 設定引數
        HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;
        request.CookieContainer = cookie;
        request.Method = "GET";
        request.ContentType = "text/plain;charset=utf-8";

        if (headers != null)
        {
            foreach (string key in headers.Keys)
            {
                request.Headers.Add(key, headers[key]);
            }
        }

        //傳送請求並獲取相應迴應資料
        HttpWebResponse response = await request.GetResponseAsync() as HttpWebResponse;
        //直到request.GetResponse()程式才開始向目標網頁傳送Post請求
        Stream instream = response.GetResponseStream();
        StreamReader sr = new StreamReader(instream, Encoding.UTF8);
        //返回結果網頁（html）程式碼
        string content = sr.ReadToEnd();
        return content;
    }
    catch (Exception ex)
    {
        LogUtil.Error(ex);
        return string.Empty;
    }
}

測試程式碼：

/// <summary>
/// 測試1
/// </summary>
private async void button1_Click(object sender, EventArgs e)
{
    //task是自己寫的獨立執行緒池，為了防止測試過程對CLR執行緒池和非同步執行緒池造成干擾
    _task.Run(() =>
    {
        Thread.Sleep(200);

        int workerThreads1, completionPortThreads1, workerThreads2, completionPortThreads2;
        ThreadPool.GetMaxThreads(out workerThreads1, out completionPortThreads1);
        ThreadPool.GetAvailableThreads(out workerThreads2, out completionPortThreads2);
        Log("假非同步 已使用輔助執行緒：" + (workerThreads1 - workerThreads2) + ", 已使用非同步執行緒：" + (completionPortThreads1 - completionPortThreads2));
    });

    string str = await GetDataAsync();
}

/// <summary>
/// 測試2 
/// </summary>
private async void button2_Click(object sender, EventArgs e)
{
    //task是自己寫的獨立執行緒池，為了防止測試過程對CLR執行緒池和非同步執行緒池造成干擾
    _task.Run(() =>
    {
        Thread.Sleep(200);

        int workerThreads1, completionPortThreads1, workerThreads2, completionPortThreads2;
        ThreadPool.GetMaxThreads(out workerThreads1, out completionPortThreads1);
        ThreadPool.GetAvailableThreads(out workerThreads2, out completionPortThreads2);
        Log("真非同步 已使用輔助執行緒：" + (workerThreads1 - workerThreads2) + ", 已使用非同步執行緒：" + (completionPortThreads1 - completionPortThreads2));
    });

    string str = await GetDataAsync2();
}

/// <summary>
/// 假非同步
/// </summary>
private async Task<string> GetDataAsync()
{
    return await Task.Run<string>(() =>
    {
        //介面耗時大約1秒
        return HttpUtil.HttpGet("http://localhost:8500/api/test/TestGet?val=1", null, null);
    });
}

/// <summary>
/// 真非同步
/// </summary>
/// <returns></returns>
private async Task<string> GetDataAsync2()
{
    //介面耗時大約1秒
    return await HttpUtil.HttpGetAsync("http://localhost:8500/api/test/TestGet?val=1", null, null);
}

測試截圖：

我想知道 WebRequest 類的 GetResponseAsync 方法是怎麼實現的，反正使用.NET提供的類，我是無法實現這樣的方法。

這篇隨筆如果有錯誤，請指正，我只是拋磚引玉，提出疑問或者說假設。