在解析和读取FTP文件之前处理C＃流 [英] C# Stream disposed before ending parsing and reading FTP File

问题描述

我正在从FTP服务器读取CSV文件并在运行中解析它。然而，我偶然发现了正在读取的文件中间的 System.ObjectDisposedException 。
我知道理所当然正在读取文件，因为我的控制台已经给我输出了。

我在网上找到的大多数答案都是关于在阅读完成之前关闭流/解析器的人，但在代码中看不到这样的错误。

以下是有问题的方法：

  public static void readCSVfromFTP字符串ftpFileAddress）
 {
 //设置FTP请求
 FtpWebRequest ftpRequest =（FtpWebRequest）FtpWebRequest.Create（ftpFileAddress）; 
 ftpRequest.Credentials = new NetworkCredential（ftpUsername，ftpPassword）; 
 ftpRequest.Method = WebRequestMethods.Ftp.DownloadFile; 
 FtpWebResponse response =（FtpWebResponse）ftpRequest.GetResponse（）; 
 
 //设置响应流&编码
流responseStream = response.GetResponseStream（）; 
 
 //文本解析器
 using（TextFieldParser parser = new TextFieldParser（responseStream））
 {
 //文本解析器设置
 parser.SetDelimiters（new string [] {，}）; 
 parser.HasFieldsEnclosedInQuotes = false; 
 
 //文本标记逻辑&文件解析
（（！parser.EndOfData）
 {
 //定义列
 string [] fields = parser.ReadFields（）; 
 // int eanNumber = int.Parse（fields [0]）; 
 // int catalogueNumber = int.Parse（fields [1]）; 
 // double quantity = double.Parse（fields [2]）; 
 // DateTime availibilityDate = Convert.ToDateTime（fields [3]）; 
 Console.WriteLine（fields [0] ++ fields [1]）; 
} 
} 
 
 //清理并关闭流
 responseStream.Close（）; 
 response.Close（）; 
} 
  

我应该补充一点，错误突出显示的行是：

  while（！parser.EndOfData）
  

编辑：

我找到了问题与精确相同的问题，但尚未得到答复。不幸的是，他们的解决方案并不满足我。

解决方案

一旦没有更多数据可用，从parser.ReadFields （）变成nothing / null。所以一个解决方法是用while（true）替换while（！parser.EndOfData），然后每次迭代检查字段是否为null，如果是的话早点退出循环。

在Visual Basic中，它看起来像这样：

  True True 
尝试
 currentRow = MyReader。 ReadFields（）
如果currentRow是Nothing然后
退出而
结束如果
'现在做所有其他
结束尝试
结束时
  

我不是C＃（或VB）的专家，即使如此，我也会冒险猜测C＃相当于：

  while（true）
 {
 //定义列
 string [] fields = parser.ReadFields（）; 
 if（fields == null）{
 break; 
} 
 // int eanNumber = int.Parse（fields [0]）; 
 // int catalogueNumber = int.Parse（fields [1]）; 
 // double quantity = double.Parse（fields [2]）; 
 // DateTime availibilityDate = Convert.ToDateTime（fields [3]）; 
 Console.WriteLine（fields [0] ++ fields [1]）; 
} 
  

也许有人对它更熟悉一点可能足以解决任何问题语法错误。

由于@casperOne表示真正的答案将在TextFieldParser的源代码中 - 这对我来说看起来像一个错误。

I am reading a CSV file from an FTP server and parsing it on the fly.

However, I stumbled upon System.ObjectDisposedException in the middle of the file being read. I know for granted that the file is being read, since my console is already giving me output.

Most of the answers I found online are regarding people closing the stream/parser before the reading is completed, but I cannot see such a mistake in my code.

Here is the problematic method:

public static void readCSVfromFTP(string ftpFileAddress)
    {
        // Setup FTP Request
        FtpWebRequest ftpRequest = (FtpWebRequest)FtpWebRequest.Create(ftpFileAddress);
        ftpRequest.Credentials = new NetworkCredential(ftpUsername, ftpPassword);
        ftpRequest.Method = WebRequestMethods.Ftp.DownloadFile;
        FtpWebResponse response = (FtpWebResponse)ftpRequest.GetResponse();

        // Setup Response Stream & encoding
        Stream responseStream = response.GetResponseStream();

        // Text parser
        using (TextFieldParser parser = new TextFieldParser(responseStream))
        {
            // Text parser settings
            parser.SetDelimiters(new string[] { "," });
            parser.HasFieldsEnclosedInQuotes = false;

            // Text tokenization logic & file parsing
            while (!parser.EndOfData)
            {
                // Define columns
                string[] fields = parser.ReadFields();
                //int eanNumber = int.Parse(fields[0]);
                //int catalogueNumber = int.Parse(fields[1]);
                //double quantity = double.Parse(fields[2]);
                //DateTime availibilityDate = Convert.ToDateTime(fields[3]);
                Console.WriteLine(fields[0] + " " + fields[1]); 
            }
        }

        // Clean up and close streams
        responseStream.Close();
        response.Close();
    }

I should add, that the line which error highlights is:

while (!parser.EndOfData)

EDIT:

I have found a question with the exact same problem, yet it is unanswered. Unfortunately, their solution doesn't satisfy me.

解决方案

Once there is no more data available, the value returned from parser.ReadFields() becomes nothing / null. So a workaround is to replace the while (!parser.EndOfData) with a While (true) and then each iteration check if fields is null, exiting the loop early if it is.

In Visual Basic it looks like this:

While True
            Try
                currentRow = MyReader.ReadFields()
                If currentRow Is Nothing Then
                    Exit While
                End If
                'Now do everything else
            End Try
        End While

I'm no expert on C# ( or VB for that matter), even so I'll hazard a guess that the C# equivalent would look something like:

while (true)
        {
            // Define columns
            string[] fields = parser.ReadFields();
            if (fields == null){
               break;
               } 
            //int eanNumber = int.Parse(fields[0]);
            //int catalogueNumber = int.Parse(fields[1]);
            //double quantity = double.Parse(fields[2]);
            //DateTime availibilityDate = Convert.ToDateTime(fields[3]);
            Console.WriteLine(fields[0] + " " + fields[1]); 
        }

Perhaps someone with a bit more familiarity with it might be kind enough to fix any syntax errors in the above.

As @casperOne says the real answer would be within the source of TextFieldParser - this looks like a bug to me.

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