CODEWITHSUNDEEP
c#streamwriter
vettori
vettori

Reputation: 761

how to use StreamWriter class properly?

I am using StreamWriter class for file operations, are there any problems in this code that I am not seeing?

Such as do I need to put it into a try catch finally block? 

StreamWriter sr = new StreamWriter(streamFolder);
sr.Write(details);

File.SetAttributes(streamFolder, FileAttributes.Hidden);
sr.Close();

Upvotes: 11

Views: 57311

Answers (5)

oleksii
oleksii

Reputation: 35905

Wrap it in a using block

using(StreamWriter sr = new StreamWriter(streamFolder))
{
      sr.Write(details);
      File.SetAttributes(streamFolder, FileAttributes.Hidden);
}

Make sure your naming is good, so streamFolder should probably be an fName. You can also put this code into try-catch-finally, if you feel you can handle some IO (or other) exceptions:

StreamWriter sr;
try
{
    sr = new StreamWriter(streamFolder);
    sr.Write(details);
    File.SetAttributes(streamFolder, FileAttributes.Hidden);
}
catch(IOException ex)
{
    //handling IO
}
finally
{
    if (sr != null)
        sr.Dispose();
}

Upvotes: 5

Sergey Berezovskiy
Sergey Berezovskiy

Reputation: 236208

Whats wrong with your code? If some exception will occur before you close stream, then stream will stay open, and system resources will not be released:

StreamWriter sr = new StreamWriter(streamFolder);
sr.Write(details);
// some exception occurs here 
File.SetAttributes(streamFolder, FileAttributes.Hidden);
sr.Close();

So, you need to be sure, that stream will be closed. This could be achieved by try...finally block:

StreamWriter sr = new StreamWriter(streamFolder);

try 
{
   sr.Write(details);
   // some exception occurs here 
   File.SetAttributes(streamFolder, FileAttributes.Hidden);
}
finally
{
   sr.Close();
}

But StreamWriter implements IDisposable interface, so you can let C# compiler do it automatically for you by wrapping writer usage into using block: 

using(StreamWriter sr = new StreamWriter(streamFolder)) 
{
   sr.Write(details);
   // some exception occurs here 
   File.SetAttributes(streamFolder, FileAttributes.Hidden);
}

This code will be compiled as:

StreamWriter sr = new StreamWriter(streamFolder);

try 
{
   sr.Write(details);
   // some exception occurs here 
   File.SetAttributes(streamFolder, FileAttributes.Hidden);
}
finally
{
   if (sr != null)
      sr.Dispose();
}

The only difference between manual implementation is null-check and method Dispose is called instead of Close. But actually when you call Close() or Dispose() same code will be executed:

this.Dispose(true);
GC.SuppressFinalize(this);

You can read more on Dispose method implementation.

Upvotes: 39

user1485585
user1485585

Reputation: 49

System.IO.StreamWriter is a System.IDisposable

You have to dispose it. And why do you close something you don't open ?

Upvotes: -3

Daniel Sklenitzka
Daniel Sklenitzka

Reputation: 2236

You should probably use a using statement:

using (StreamWriter sr = new StreamWriter(streamFolder))
{
    sr.Write(details);
    File.SetAttributes(streamFolder, FileAttributes.Hidden);
}

At the end of the using block, the StreamWriter.Dispose will be called, whether there was an exception or the code ran successfully.

Upvotes: 7

John Saunders
John Saunders

Reputation: 161773

You want to use:

  using (StreamWriter sr = new StreamWriter(streamFolder))
  {
      sr.Write(details); 

      File.SetAttributes(streamFolder, FileAttributes.Hidden); 
  }

You don't need the Close.

Upvotes: 5

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