C# 嵌套foreach循环的性能问题

我不知道我面临的问题是由于嵌套循环还是其他原因（错误代码、大数据）。让我解释一下，希望有人能帮我弄明白：-

我正在开发一个WindowsPhone8应用程序。启动时，应用程序对3个不同的页面进行三次httpclient调用，然后将每个响应（html）转换为xml，然后再转换为json数据（OBS！！！这很好，没有问题）。在这个阶段，我想从这3个json中提取数据，并将提取的数据合并成一个新的json，稍后保存到IsolatedStorage中。为了进行提取，我使用了多个foreach循环，甚至有时使用linq（我认为这就是问题所在）。每个foreach循环可能进行50到>500次迭代。提取过程几乎需要2分钟，我认为这是非常重要的。下面您可以看到我的代码中的代码片段：-

public async Task LoadData()
    {

        //baseUri definition....

        await CookieHandler.GetCookies(baseUri);

        _reqPList=new RequestResponse();

        await _reqPList.GetResponse(baseUri, pList);  // First page request
        XmlConvertor.ConvertToXml(_reqPList.Response);  //First page convert to xml
        var phoneListResponse = XmlConvertor.XmlString;

        //Second and third page request and convert to xml

        var handler = new DataHandler();
        await handler.phoneListHandler(phoneListResponse);  //First page convert to Json
        //Second and third page convert to Json

        var jObject = JObject.Parse(handler.PhoneListJson);
        var jCollection = jObject["tbody"]["tr"].Children();

        //The start of extracting data

        using (var stream = new MemoryStream())
        using (var streamWriter=new StreamWriter(stream))
        using (_jsonW = new JsonTextWriter(streamWriter))
        {
                var watch = Stopwatch.StartNew();
            _jsonW.WriteStartArray();
            foreach (var item in jCollection)  //First foreach loop (100 iteration) using the first page
            {
                var arr = item.Value<JArray>("td");
                if (arr == null) continue;
                _jsonW.Formatting = Formatting.Indented;
                _jsonW.WriteStartObject();
                _jsonW.WritePropertyName("Name");
                _jsonW.WriteValue(arr[0].Value<string>());
                #region Info Array
                _jsonW.WritePropertyName("Info");
                _jsonW.WriteStartArray();

                // Do some extraction

                _jsonW.WriteEndArray();
                #endregion
                #region Schedule Array
                await ScheduleArrayAsync(item, handler.ScheduleJson, handler); // This method extract data from 2nd page
                #endregion
                #region Current activity
                CurrActivityAsync(item, handler.CurrActivitiesJson); // This method extract data from 3rd page
                #endregion
                _jsonW.WriteEndObject();
            }
            _jsonW.WriteEndArray();
                watch.Stop();
                var j = watch.ElapsedMilliseconds;

            await streamWriter.FlushAsync();
            stream.Position = 0;
            using (var streamReader=new StreamReader(stream))
            {
                var json = await streamReader.ReadToEndAsync();
            }
        }
        this.IsDataLoaded = true;
    }

    private void CurrActivityAsync(JToken token, string jString) This method is called 1 time only
    {
        var arr = token.Value<JArray>("td");
        var personNameArray = arr[0].Value<string>().Split(',');
        if (!_owner.Contains(personNameArray[0])) return;
        var jObject = JObject.Parse(jString);
        var jCollection = jObject["tbody"]["tr"].Children();

        _jsonW.WritePropertyName("Current activity");
        _jsonW.WriteStartArray();

        foreach (var array in from item in jCollection   // Second foreach loop (Almost 60 iteration)
            let array = item.Value<JObject>().Value<JArray>("td")
            where array != null && item.Children().Count() > 1
            select array)
        {
            _jsonW.WriteStartObject();

            // do some extraction 

            _jsonW.WriteEndObject();
        }
        _jsonW.WriteEndArray();
    }

    private async Task ScheduleArrayAsync(JToken token, string jString, DataHandler handler)  // This method is called 100 times.
    {
        var arr = token.Value<JArray>("td");
        var personNameArray = arr[0].Value<string>().Split(',');
        var jObject = JObject.Parse(jString);
        var trList = jObject["tbody"]["tr"];
        var selectedArray = default(JArray);
        var weekNumber = trList.SelectMany(tr => tr.SelectTokens("td[1].table.tbody.tr", false))
            .SelectMany(lk => lk.SelectTokens("td", false))
            .Where(j => (!j.HasValues) && (j.Value<string>().Contains("v")))
            .Select(lo => lo.Value<string>())
            .ToArray();

        var psTypeOne = trList.SelectMany(tr => tr.SelectTokens("td[0].a.#text", false))
            .Where(hashText => (hashText.Value<string>().Contains(personNameArray[0])) &&
                         (hashText.Value<string>().Contains(personNameArray[1])))
            .Select(td => td.Parent.Parent.Parent.Parent.Parent)
            .ToArray();


        if (psTypeOne != null)
        {
            _jsonW.WritePropertyName("Schedule");
            _jsonW.WriteStartArray();
            _jsonW.WriteStartObject();
            _jsonW.WritePropertyName("Week Number");
            _jsonW.WriteValue(weekNumber[0].Remove(0, 2));
            _jsonW.WritePropertyName("Week days");
            _jsonW.WriteStartArray();

            foreach (var day in selectedArray) // 7 itereation
            {
                if (day.SelectToken("table", false) == null) continue;
                _jsonW.WriteStartObject();
                _jsonW.WritePropertyName("Day name");
                var dayname = Convert.ToDateTime(day.Value<string>("@id").Remove(0, 8));
                _jsonW.WriteValue(dayname.DayOfWeek.ToString());
                _jsonW.WritePropertyName("Date");
                _jsonW.WriteValue(day.Value<string>("@id").Remove(0, 8));
                var assignments = day.SelectToken("table.tbody.tr", false);
                _jsonW.WritePropertyName("Assignments");
                _jsonW.WriteStartArray();

                //Foreach loop 2 start or Foreach
                foreach (var assignment in assignments) // between 1 and 5 iterations
                {
                    //Some extractions

                        if (info[0].Contains("slotInfo")) //Here we do some new webrequests and extractions
                        {
                            await _reqPList.GetSlotInfoPost(info[1]);
                            XmlConvertor.ConvertToXml(_reqPList.Response);
                            addedInfo = XmlConvertor.XmlString;
                            await handler.InfoHandler(addedInfo);
                            var jO = JObject.Parse(handler.InfoJson);
                            addedJToken = jO.SelectToken("td");

                            // Some extractions

                        }
                    }
                    else
                    {
                        // Some code
                    }
                }
                //Foreach loop 2 end
                //Some code to Close the Array
            }
            //Foreach loop 1 end
            //some code to Close the Array
        }
    }

---

OBS！！！我知道json数据需要关闭，这只是为了说明一点。

我认为从httprequest响应简单地遍历html可能更简单

使用serializable属性准确表示最终对象的自定义类，以及填充该类时调用javascript序列化程序将所有内容序列化为json对象（您可以使用联机将自定义类中的json转换为json，这样您就可以简单地将json反序列化为自定义对象，而不会出现问题，反之亦然）

还有另一件重要的事情：数据维度。如果您使用的数据较少，是否会更快？如果您使用的是大数据，则需要更多的时间做出响应，并需要更多的时间进行处理

---

您能告诉我们哪些是包含的页面，哪些是最终的json对象吗？

handler.InfoHandler（addedInfo）做什么？是否有异步的原因？@siride handler.InfoHandler（addedInfo）是对异步方法的调用，用于将数据从xml转换为json。我分析的原始3页中没有这段数据。为什么在这里需要使用异步？通过这种方式比同步方式节省时间真的是性能密集型的吗？我以前试过htmlagility Pack，但它不适合我的需要。无论如何，我认为这不是问题所在。请看一下编辑后的信息。您将看到，将原始Json转换为我的Json并非易事，需要手动提取数据。如果你认为我误解了你的答案，请给我举个例子，让我更好地理解。

<tr class="odd">
<td class="user" onmouseover="userInfo('469');" onmouseout="userInfo(0);" onmousemove="moveSlotInfo();"> User One</td> // User One is needed
<td id="day-469-2014-03-31" style="vertical-align: top;">
  <table class="ss" cellspacing="1">
    <tbody>
      <tr>
        <td class="as"> </td>
      </tr>
    </tbody>
  </table>
</td>
<td id="day-469-2014-04-01" style="vertical-align: top;">   // The date is needed
  <table class="ss" cellspacing="1">
    <tbody>
      <tr>
        <td class="as" style="color: #ffffff; background-color: #4040ff;" onmouseover="this.className=(document.week_vs_doctor.activityId.value==-1?'sd':'sp');slotInfo('177738',false);" onmouseout="this.className='as';slotInfo(0,false);" onmousemove="moveSlotInfo();">KAVAul</td>  // KAVAul is needed
      </tr>
    </tbody>
  </table>
</td>

[
{
"Name": "User Name",
"Info": [
  {
    "Signature": "un"
  },
  {
    "Group": "Group1"
  },
  {
    "E-mail": "user.name@group1.com"
  }
],
"Schedule": [
  {
    "Week Number": "14",
    "Week days": [
      {
        "Day name": "Monday",
        "Date": "2014-03-31",
        "Assignments": [
          {
            "Assignment name": "AAA",
            "Assignment time": "07:30 - 16:00",
            "Assignment provider": "BBB, 2014-03-07 16:42"
          }