asp.net MVC应用程序中的文件读写内存泄漏

Question

Intailly I read the json string from text file and converting the json string to object and add it to the list. Then I am calling the instagram feed API in loop, after getting the response I am converting the response string to json object and add it to list. Finally I am converting the list of objects to json string and write it to the text file.

I need to update the json string in two text files, so after completing all the request to instagram, I am copying the json string from one text file to another text file.

My problem

I am calling this InstagramRecentList method in every 10 minutes to reflect the recent instagram feeds in my web site. When I check the Memory usage in server, this application pool occupy more memory also in one stage all the apps hosted in IIS stops wroking because of this. What is the best and efficient way to do above process so that my application do not occupy more memory.

Here is the screen shot with the selected process shows memory usage of that application pool, as of now i am recycling the app pool every day. If I stop recycling the app pool, the memory usage get increased. Please help me. Sorry for my English.

public ActionResult InstagramRecentList()
{
    string filepath = Path.Combine(ConfigurationManager.AppSettings["instgramfilepath"], Constants.w_Instagram_recent_listJsonFile);

    string ClientId = ConfigurationManager.AppSettings["instgramclientid"];
    string HondaId = ConfigurationManager.AppSettings["instgramhondaid"];
    WriteInstagramRecentList(filepath, HondaId, ClientId);
    string wp = Path.Combine(ConfigurationManager.AppSettings["instgramfilepath"], Constants.r_Instagram_recent_listJsonFile);
    string Jsonstring = String.Empty;
    using (StreamReader sr = System.IO.File.OpenText(filepath))
    {
        string s = String.Empty;
        while ((s = sr.ReadLine()) != null)
        {
            Jsonstring = Jsonstring + s;
        }
    }

    TextWriter tw = new StreamWriter(wp);
    tw.WriteLine(Jsonstring);
    tw.Close();
    tw.Dispose();
    return View("UpdateResult");
}

private static void WriteInstagramRecentList(string filepath, string HondaId, string ClientId, string nextpageurl = null)
{
    string feedurl = string.Empty;
    List<object> modeldata = new List<object>();
    if (nextpageurl != null)
    {
        feedurl = nextpageurl;

        string Jsonstring = String.Empty;
        using (StreamReader sr = System.IO.File.OpenText(filepath))
        {
            string s = String.Empty;
            while ((s = sr.ReadLine()) != null)
            {
                Jsonstring = Jsonstring + s;
            }
        }
        if (!string.IsNullOrEmpty(Jsonstring))
        {
            modeldata = JsonConvert.DeserializeObject<List<object>>(Jsonstring);
        }
    }
    else
    {
        feedurl = String.Format("https://api.instagram.com/v1/users/{0}/media/recent/?client_id={1}&count={2}", HondaId, ClientId, 200);
    }

    var request = WebRequest.Create(feedurl);
    request.ContentType = "application/json; charset=utf-8";
    string text;
    var response = (HttpWebResponse)request.GetResponse();
    using (var reader = new StreamReader(response.GetResponseStream()))
    {
        text = reader.ReadToEnd();
        if (!string.IsNullOrEmpty(text))
        {
            dynamic result = System.Web.Helpers.Json.Decode(text);
            if (result.data != null)
            {
                modeldata.AddRange(result.data);
            }
            string json = JsonConvert.SerializeObject(modeldata);
            TextWriter tw = new StreamWriter(filepath);
            tw.WriteLine(json);
            tw.Close();
            tw.Dispose();
            if (result.pagination != null && !string.IsNullOrEmpty(result.pagination.next_url) && modeldata.Count < 205)
            {
                WriteInstagramRecentList(filepath, HondaId, ClientId, result.pagination.next_url);
            }

        }
    }
}

Answer 1

Do not ever use the string class directly when concatenating strings. They are immutable in C# (as in many other languages). This means that you are creating a new string each time. Use the StringBuilder class instead, and don't create a copy of each line - check EndOfStream property instead:

StringBuilder jsonString = new StringBuilder;
using (StreamReader sr = System.IO.File.OpenText(filepath))
{
    while (!sr.EndOfStream))
    {
        jsonString.AppendLine(sr.ReadLine());
    }
}

Or simply use the ReadToEnd method of the StreamReader class:

String jsonString = String.Empty;
using (StreamReader sr = System.IO.File.OpenText(filepath))
{
     jsonString = sr.ReadToEnd();
}

You can combine these methods too. Another thing that you should check when working with graphics - are you creating some images according the response of Instagram? If so, consider disposing them after use. You can use the using pattern on the TextWriter object too, like this:

using (TextWriter tw = new StreamWriter(wp))
{
    tw.WriteLine(Jsonstring);
}

Putting it all together, you can rewrite your method as such:

using (StreamReader sr = System.IO.File.OpenText(filepath))
using (TextWriter tw = new StreamWriter(wp))
{
    tw.WriteLine(sr.ReadToEnd());
}

Answer 2

My first suggestion is - try to avoid recursive call of the
WriteInstagramRecentList method.