Stream Reader out of memory exception

Posted on 2011-03-14
Last Modified: 2012-06-27
I am using StreamReader to read in a text file in 2005
My problem is at the.last line 1 text file is malformed
it does not have a LFCR
so it keeps reading

I end up with 150 Megs read in and then it throws this error

System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.
   at System.String.GetStringForStringBuilder(String value, Int32 startIndex, Int32 length, Int32 capacity)
   at System.Text.StringBuilder.GetNewString(String currentString, Int32 requiredLength)
   at System.Text.StringBuilder.Append(Char[] value, Int32 startIndex, Int32 charCount)
   at System.IO.StreamReader.ReadLine()

My lines are at most 164 characters not counting the LFCR

I need a way to tell stream reader to stop reading after a 165 characters
any idea

Dim sr As StreamReader = File.OpenText(filename)
Do Until sr.Peek = -1
linecontent = sr.ReadLine
If Trim(linecontent) <> "" Then

If Trim(Mid(linecontent, 79, 8)) <> "" Then
aDate1 = Mid(linecontent, 79, 8)
aDate1 = Mid(aDate1, 5, 2) & "/" & Mid(aDate1, 7, 2) & "/" & Mid(aDate1, 1, 4)
aDate1 = "12/31/1849"
 End If

If CDate(aDate1) >= dDate
sGuest = Mid(linecontent, 1, 6) & "0"
End IF

Other code here that works fine

End IF
linecontent = String.Empty

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Question by:hainansyndrome
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Expert Comment

ID: 35133201
Try this method:

Using sr As New StreamReader(<path>)
  While Not sr.EndOfStream
     'your code here for parsing
  End While
End Using 'this closes and disposes the stream

Open in new window

PS be sure to close your streams.

Author Comment

ID: 35133277
how do I setup the Stream Reader part?
I am trying

            Dim sr As StreamReader
            Using sr As New StreamReader=File.OpenText((destination & "\" & filename)

but i get end of Statement expected?

Author Comment

ID: 35133329
sing sr As New StreamReader=File.OpenText((destination & "\" & filename)

is not working
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Author Comment

ID: 35133398
ok never mind i have dain bramage

but that did not help
it still hit the last line and blew up

see the last line is about 170 megs since there are no LFCR
LVL 86

Expert Comment

by:Mike Tomlinson
ID: 35133404
May we see all the code?...

Author Comment

ID: 35133439
I have shown all the relevant code
the problem is on the last line of the text file
LVL 86

Expert Comment

by:Mike Tomlinson
ID: 35133473
You've shown all the code that YOU think is relevant...but you were unable to solve the problem.  If you show us all the code we may spot a problem that you are unaware of.  Just saying...

Author Comment

ID: 35133532
Idle_Mind: I have show you all the relevant code
I know with 10000000% certainty the remaining code has no flaws
I have trappend this error
I know when and where it is occuring
LVL 86

Expert Comment

by:Mike Tomlinson
ID: 35133927
The "OutOfMemoryException" part throws up a red flag.  It indicates that you were low on memory, which shouldn't be the case if you are only reading LINE BY LINE and each line is no longer than 164 chars.

Are you by chance, in that code you are sure is not the problem, building up a huge value with simple string concatenation?

    str = str & someDataExtractedFromEachLine

Or in short hand:

    str &= someDataExtractedFromEachLine

Expert Comment

ID: 35134895
Why is the last line 170 megs? Maybe you need to rethink the file design.
LVL 86

Expert Comment

by:Mike Tomlinson
ID: 35134917
If you need to control how much is read at a time then use a straight FileStream() and then you can read by a specified number of bytes:

...but then you lose the built-in ability to read only the next line.  You have to manually look for the CRLF 's in the returned array of bytes and break up the data yourself.
LVL 18

Accepted Solution

deighton earned 125 total points
ID: 35136902
do you need to use a binary reader?

Author Comment

ID: 35137444
I fixed it
must have been the fact that I had 8 VS windows open or that I have not rebooted in 4 days
after reboot the  .substring showed up

I was able to use
Dim sLen As Integer = 160
linecontent = sr.ReadLine.Substring(0, sLen)
I then later incremented up to 164 characters using a Try Catch
LVL 86

Expert Comment

by:Mike Tomlinson
ID: 35137548
Just for clarification, though, if the last line really is ~super~ long...your method directly above is NOT reading just 160 characters.  It is still reading the ENTIRE line and then Substring() is simply returning the requested number of chars.  This apparently is only working because you have enough memory available.  To truly read only the limited number of chars you'd have to use the lower level FileStream.Read() method as I mentioned earlier, or you something similar like BinaryReader() as deighton suggests.

Author Comment

ID: 35139286
I stand corrected
same problem
it hits the last line and bam


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