"The process cannot access the file because it is being used by another process"

Question

The full error I am receiving is:

"The process cannot access the file 'e:\Batch\NW\data_Test\IM_0232\input\RN318301.WM' because it is being used by another process.>>> at IM_0232.BatchModules.BundleSort(String bundleFileName) at IM_0232.BatchModules.ExecuteBatchProcess()"

The involved code can be seen below. The RN318301.WM file being processed is a text file that contains information which will eventually be placed in PDF documents. There are many documents referenced in the RN318301.WM text file with each one being represented by a collection of rows. As can be seen in the code, the RN318301.WM text file is first parsed to determine the number of documents represented in it as well as the maximum number of lines in a documents. This information is then used to create two-dimensional array that will contain all of the document information. The RN318301.WM text file is parsed again to populate the two-dimensional array and at the same time information is collected into a dictionary that will be sorted later in the routine.

The failure occurs at the last line below:

File.Delete(_bundlePath + Path.GetFileName(bundleFileName));

This is a sporadic problem that occurs only rarely. It has even been seen to occur with a particular text file with which it had not previously occurred. That is, a particular text file will process fine but then on reprocessing the error will be triggered.

Can anyone help us to diagnose the cause of this error? Thank you very much...

public void BundleSort(string bundleFileName)
    {

        Dictionary<int, string> memberDict = new Dictionary<int, string>();
        Dictionary<int, string> sortedMemberDict = new Dictionary<int, string>();
        //int EOBPosition = 0;
        int EOBPosition = -1;
        int lineInEOB = 0;
        int eobCount = 0;
        int lineCount = 0;
        int maxLineCount = 0;
        string compareString;
        string EOBLine;
        //@string[][] EOBLineArray;
        string[,] EOBLineArray;

        try
        {
            _batch.TranLog_Write("\tBeginning sort of bundle " + _bundleInfo.BundleName + " to facilitate householding");

            //Read the bundle and create a dictionary of comparison strings with EOB position in the bundle being the key

            StreamReader file = new StreamReader(@_bundlePath + _bundleInfo.BundleName);

            //The next section of code counts CH records as well as the maximum number of CD records in an EOB.  This information is needed for initialization of the 2-dimensional EOBLineArray array.

            while ((EOBLine = file.ReadLine()) != null)
            {
                if (EOBLine.Substring(0, 2) == "CH" || EOBLine.Substring(0, 2) == "CT")
                {
                    if (lineCount == 0)
                        lineCount++;

                    if (lineCount > maxLineCount)
                    {
                        maxLineCount = lineCount;
                    }
                    eobCount++;
                    if (lineCount != 1)
                        lineCount = 0;

                }
                if (EOBLine.Substring(0, 2) == "CD")
                {
                    lineCount++;
                }
            }

            EOBLineArray = new string[eobCount, maxLineCount + 2];


            file = new StreamReader(@_bundlePath + _bundleInfo.BundleName);


                try
                {



                    while ((EOBLine = file.ReadLine()) != null)
                    {

                        if (EOBLine.Substring(0, 2) == "CH")
                        {
                            EOBPosition++;
                            lineInEOB = 0;
                            compareString = EOBLine.Substring(8, 40).Trim() + EOBLine.Substring(49, 49).TrimEnd().TrimStart() + EOBLine.Substring(120, 5).TrimEnd().TrimStart();
                            memberDict.Add(EOBPosition, compareString);

                            EOBLineArray[EOBPosition, lineInEOB] = EOBLine;

                        }
                        else
                        {
                            if (EOBLine.Substring(0, 2) == "CT")
                            {
                                EOBPosition++;
                                EOBLineArray[EOBPosition, lineInEOB] = EOBLine;
                            }
                            else
                            {
                                lineInEOB++;
                                EOBLineArray[EOBPosition, lineInEOB] = EOBLine;

                            }
                        }

                    }
                }
                catch (Exception ex)
                {
                    throw ex;
                }
                _batch.TranLog_Write("\tSending original unsorted bundle to archive");
           if(!(File.Exists(_archiveDir + "\\" +DateTime.Now.ToString("yyyyMMdd")+ Path.GetFileName(bundleFileName) + "_original")))
             {
                 File.Copy(_bundlePath + Path.GetFileName(bundleFileName), _archiveDir + "\\" +DateTime.Now.ToString("yyyyMMdd")+ Path.GetFileName(bundleFileName) + "_original");
             }


                file.Close();
                file.Dispose();
            GC.Collect();

                File.Delete(_bundlePath + Path.GetFileName(bundleFileName));

Answer 1

You didn't close/dispose your StreamReader first time round so the file handle is still open

Consider using the using construct - this will automatically dispose of the object when it goes out of scope:

using(var file = new StreamReader(args)) 
{
    // Do stuff
}

// file has now been disposed/closed etc

Answer 2

You need to close your StreamReaders for one thing.

StreamReader file = new StreamReader(@_bundlePath + _bundleInfo.BundleName);

You need to close the StreamReader object, and you could do this in a finally block:

finally {
  file.Close();
}

A better way is to use a using block:

using (StreamReader file = new StreamReader(@_bundlePath + _bundleInfo.BundleName)) {
    ...
}

It looks to me like you are calling GC.Collect to try to force the closing of these StreamReaders, but that doesn't guarantee that they will be closed immediately as per the MSDN doc: http://msdn.microsoft.com/en-us/library/xe0c2357.aspx

From that doc: "All objects, regardless of how long they have been in memory, are considered for collection;"