Qn: Getting Around Windows File Lockup Property Using C# -- using FileStream & Stream Writer

EDN Admin · Feb 23, 2012

I am encountering a problem in developing a software for my business. The task I am trying to achieve is that, I need to update a file (.txt) while that file is being constantly accessed by another program. 
 
 
The ultimate setting is this: I will have a software running, constantly reading the content of a feed file (call it info.txt). I have another script running, constantly updating the feed file (info.txt). 
 
 
I realized the serious conflict in using the file after I implemented the above setting. With the software (call it AAA) running, I cant make an edit to info.txt even manually. I open up info.txt, make a change, and click save, windows return an error
message: "The process cannot access the file because it is being used by another process." If I try to delete info.txt, the error message is "the action cant be completed because the file is open in AAA.exe". 
When I run my (java) script that constantly updates info.txt, the file IO exception is: java.io.FileNotFoundException: info.txt (The process cannot access the file because it is being used by another process) 
 
 
The part of feature in software AAA I am using is not yet fully developed to be publicly released. (Its a foreign software to my enterpise so I cant modify its behavior/source code.) The way it is accessing files locks up the file completely.
I thought of temperarily pointing away the reference to info.txt in the softwares profile files to allow a temparory edit, but this approach would fail because with AAA running (and I need it to), I cant make any change to any file its using. 
 
I consulted one of the main developer of software AAA. He acknowledges this is an issue right now, he would improve it in next release. But meanwhile I would like the set up to work. He told me he programs with .NET, and he provided a line that could help
me to get around my problem: 
 
FileStream fs = new FileStream(@"info.txt", FileMode.OpenOrCreate, FileAccess.Write, FileShare.ReadWrite); 
 
Supposedly, by supplying these arguments, this filestream are allowed to be shared on both writes and reads. 
 
 
I am a java programmer, and Ive had no experience with .NET. However I did some research and learning, I realized his code is the syntex of C#, which runs in the CLR of .NET framework. I set up C# on my computer and studied some C# beginer tutorial, and
comes up with the following script, hoping to solve my problem. 
 
 
If its really true that C# allows to change the access property of a file at a fundamental level, I would open up the filestream of info.txt, allowing it to be shared with both read and write. Once I do that, I can run my script of updating info.txt,
and then run the software AAA that keeps refreshing info.txt. 
 
Trying to achieve the above implementation, I come up with a C# script: 
 
================================================
 
using System; 
using System.IO; 
 
class CopyFeed 
{ 
static void Main() 
{ 
string fileName1 = "info.txt"; 
<span style="white-space

re <span style="white-space

re string fileName2 = "info2.txt"; 
<span style="white-space

re 
<span style="white-space

re 
FileStream fs = new FileStream(@fileName1, FileMode.OpenOrCreate, FileAccess.Write, FileShare.ReadWrite); 
<span style="white-space

re <span style="white-space

re StreamWriter sw = null; 
<span style="white-space

re 
<span style="white-space

re <span style="white-space

re // attempting to unlock part of the file, didnt work 
<span style="white-space

re <span style="white-space

re /* 
<span style="white-space

re <span style="white-space

re string contents = File.ReadAllText(@fileName2); 
<span style="white-space

re <span style="white-space

re fs.Unlock(0, contents.Length * 2); 
<span style="white-space

re <span style="white-space

re */ 
 
<span style="white-space

re <span style="white-space

re while (true) 
<span style="white-space

re <span style="white-space

re { 
<span style="white-space

re <span style="white-space

re Console.WriteLine("Copying Feed..."); 
<span style="white-space

re 
<span style="white-space

re <span style="white-space

re string contents = File.ReadAllText(@fileName2); 
<span style="white-space

re 
<span style="white-space

re <span style="white-space

re try 
<span style="white-space

re <span style="white-space

re { 
<span style="white-space

re <span style="white-space

re sw = new StreamWriter(fs); 
<span style="white-space

re <span style="white-space

re sw.Write(contents); 
<span style="white-space

re <span style="white-space

re } 
<span style="white-space

re <span style="white-space

re catch (Exception e) 
<span style="white-space

re <span style="white-space

re { 
<span style="white-space

re <span style="white-space

re Console.WriteLine("CopyFeed :: " + e.Message); 
<span style="white-space

re <span style="white-space

re } 
<span style="white-space

re <span style="white-space

re finally 
<span style="white-space

re <span style="white-space

re { 
<span style="white-space

re <span style="white-space

re if (sw != null)<span style="white-space

re
<span style="white-space

re {<span style="white-space

re
 
<span style="white-space

re <span style="white-space

re sw.Flush(); 
<span style="white-space

re <span style="white-space

re //sw.Close();<span style="white-space

re
 
<span style="white-space

re <span style="white-space

re } 
<span style="white-space

re <span style="white-space

re } 
<span style="white-space

re 
<span style="white-space

re <span style="white-space

re Console.WriteLine("Pausing For 2 sec..."); 
<span style="white-space

re <span style="white-space

re System.Threading.Thread.Sleep(2000); 
<span style="white-space

re 
<span style="white-space

re <span style="white-space

re } 
<span style="white-space

re 
<span style="white-space

re 
} 
} 
 
================================================ 
 
 
Supposedly, I will have my java script constantly updating info2.txt . Then I will have this C# script constantly copying the entire content of info2.txt into info.txt. 

I wish to seek help with this post in 2 aspects: 

 
1. The above script is still buggy, because all it does is keep appending to the file info.txt. I wish to find a way that I can clear the content of file at the start of every iteration and just copy over the content of file2. Right now if I execute the script,
it will create a infinitely large file as time goes. 
 
 
2. Based on the description above, is my solution going to work? Do I have any better option? (with software AAA behaviour staying the same) Is there even a way to get around it? 
 
 
Ive been working on this problem for the past few days and am really stuck. I would sincerely thank any one who offers any insight! 
 
 
 
 
 
 
 
 
 
 

 
 
 

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Qn: Getting Around Windows File Lockup Property Using C# -- using FileStream & Stream Writer

EDN Admin

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