Hello. I am trying to split a file with 334,386 lines into seperate files of
50,000 each.

This is the code i am running:

           Dim intFragmentRawIndex As Integer
           Dim swRawDataFile As StreamWriter
           Dim intNewRawIndex As Integer
           Dim strNewRawDataFileName As String
           Dim intFragmentCallCount As Integer = 0
           Dim strHeaderLine As String
           Dim blnFileClosed As Boolean = False

           strHeaderLine = colRawDataFile(1)

           CreateRawDataFragment(intParentRawIndex, intNewRawIndex,
strNewRawDataFileName)

           Dim myFileStream As New
System.IO.FileStream(strTempDirectoryPath & strNewRawDataFileName, _
                                                       
FileMode.OpenOrCreate, FileAccess.Write, FileShare.None)

           swRawDataFile = New StreamWriter(myFileStream)

           swRawDataFile.WriteLine(strHeaderLine)

           For i As Integer = 2 To colRawDataFile.Count

               If intFragmentCallCount = 50000 Then

                   'Clear Stream Writer Buffer
                   swRawDataFile.Flush()

                   'Close file
                   swRawDataFile.Close()

                   'Set Call Count against raw data file
                   SetFragmentCallCount(intNewRawIndex, intFragmentCallCount)

                   'Reset call count
                   intFragmentCallCount = 0

                   'If not on final line of raw data file....
                   If i <> colRawDataFile.Count Then

                       CreateRawDataFragment(intParentRawIndex,
intNewRawIndex, strNewRawDataFileName)

                       myFileStream = New
System.IO.FileStream(strTempDirectoryPath & strNewRawDataFileName, _
                                                       
FileMode.OpenOrCreate, FileAccess.Write, FileShare.None)

                       swRawDataFile = New StreamWriter(myFileStream)

                       swRawDataFile.WriteLine(strHeaderLine)

                   Else

                       blnFileClosed = True

                   End If

               End If

               swRawDataFile.WriteLine(colRawDataFile(i))

               intFragmentCallCount += 1

           Next

           If Not blnFileClosed Then

               'Close last fragment
               swRawDataFile.Close()

               'Set call count against last fragment
               SetFragmentCallCount(intNewRawIndex, intFragmentCallCount)

           End If

The first file creates in 3 mins.
The second file creates in 11 minutes.
The third file creates in 18 minutes.
I am still waiting for the forth file to create.

I am writing the same number of records to each file, so why would the time
it takes to write the file of the same size take longer each time?

I thought that calling the flush method of the stream would maintain
performance but this does not seem to be the case! What am i doing wrong?