the process cannot access the file because it's used by another process

Question

I'm facing a problem with my code in C# where I'm writing to csv file (saving input data from textboxes).On the same time I want to add row number to each new row saved. I wrote this code but the error is showing: Sysytem.IO.IOException 'The process cannot acess the file because it's used by another process'. I made sure I'm closing the streamwriter and streamreader. I don't know how else I can improve my code.

var filePath = "csvFile.csv";

using (StreamWriter sw = new StreamWriter(new FileStream(filePath, FileMode.Create, FileAccess.Write)))
try
{
    //Count rows in csv file and add new row number
    string file = new StreamReader("csvFile.csv").ReadToEnd();
    string[] lines = file.Split('\n');
    int countOfLines = lines.GetLength(0);

    sw.WriteLine("{0},{1},{2},{3},{4},{5}"
        , countOfLines + 1
        , txtEventName.Text
        , txtEventType.Text
        , txtAttributeName.Text
        , txtAValue.Text
        , txtEventDescrip.Text);

    // Ensure data is written to disk  
    sw.Close();
}
catch()
{
}

It would help if you provided a complete sample of your code and indent it properly. — , Oct 08 '18 at 14:51
There will never be more than one line in the CSV file, because you always create a new one by `FileMode.Create`. What you probably want to do is to open the file with `FileMode.Append`, *after* you have read its content by a StreamReader to get the number of already existing lines. However, see [this answer](https://stackoverflow.com/a/119572/1136211) for a more efficient way to get the current line count. — Clemens, Oct 08 '18 at 14:57

kmatyaszek · Answer 1 · 2018-10-08T15:27:04.403

You received this error ('The process cannot access the file because it's used by another process') because you are trying access file again by using StreamReader while it's already opened by StreamWriter.

To resolve your problem you should first count a number of lines in your file and after that, you should append new text to file.

 var countOfLines = File.ReadLines("csvFile.csv").Count();

 using (StreamWriter sw = 
            new StreamWriter(new FileStream(filePath,
                              FileMode.Create | FileMode.Append, FileAccess.Write)))
          try
          {             
                sw.WriteLine("{0},{1},{2},{3},{4},{5}",
                    countOfLines + 1,
                    txtEventName.Text
                  , txtEventType.Text
                  , txtAttributeName.Text
                  , txtAValue.Text
                  , txtEventDescrip.Text);
...

You should make attention to FileMode parameter of FileStream. You should use FileMode.Create | FileMode.Append, if you left in your code FileMode.Create you will have always one line of data in your file (msdn).

Thank You all,I solved my problem by placing code that counts csv file rows outside the StreamWriter code: //Count rows in csv file and add new row number var lineCount = 0; using (var reader = File.OpenText(@"csvFile.csv")) { while (reader.ReadLine() != null) { lineCount++; } } — Aga, Oct 08 '18 at 15:44

score 0 · Answer 2 · answered Oct 08 '18 at 14:53

0

You should access your StreamReader instance outside of the using statement for StreamWriter. It should be inside of its own using statement. You are effectively trying to read from a file that is currently also being written to.

answered Oct 08 '18 at 14:53

Charles Lambert

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the process cannot access the file because it's used by another process

2 Answers2