can't close file with FileStream

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C#

FileStream obj = new FileStream(System.Convert.ToString(row.Cells["Lec_media"].Value), FileMode.Open, FileAccess.Read, FileShare.Read);



 if (Startdate2 == JCM_NOW2)
                {
                    if (checkBox1.Checked == true)
                    {

                        try
                        {


                            obj = null;
                            System.Diagnostics.Process.Start(System.Convert.ToString(row.Cells["Lec_media"].Value));

                        }
                        finally
                        {
                            if (obj != null)
                            obj.Close();

                        }
                    }

                }



            if (Enddate2 == JCM_NOW2)
            {



                if (obj != null) ((IDisposable)obj).Dispose();

                obj.Close();

               // this code does not close the file which opened above .. why?


            }

Posted 11-Feb-15 10:50am

Golden Basim

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George Swan 11-Feb-15 16:59pm

I think it is because you have called obj.Dispose() before closing it.

Golden Basim 11-Feb-15 17:56pm

the same error after removing if (obj != null) ((IDisposable)obj).Dispose();

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Sergey Alexandrovich Kryukov · Accepted Answer · 2015-02-11T11:21:00

Solution 1

Use different pattern with stream, without explicit closing (I know, the documentation is a bit confusing):

C#

using (FileStream stream = new FileStream( /* ... */ )) {
   // use stream object here
} // stream.Dispose() is automatically called here

Besides, regardless of the closing problems, it's important to guarantee that you eventually call System.IDisposable.Dispose() for each and every object implementing this interface. That's why it's good to use the using statement (not to be confused with using directive!): https://msdn.microsoft.com/en-us/library/yh598w02.aspx[^].

One more suggestion: most likely, you don't need to use FileStream directly. It is really needed only if you have read/write stream, which is a rare case; usually, your stream is read-only or write-only. Therefore, it's usually much better to use one or more of these classes:
https://msdn.microsoft.com/en-us/library/system.io.streamwriter%28v=vs.110%29.aspx[^],
https://msdn.microsoft.com/en-us/library/system.io.streamreader%28v=vs.110%29.aspx[^],
https://msdn.microsoft.com/en-us/library/system.io.binarywriter%28v=vs.110%29.aspx[^],
https://msdn.microsoft.com/en-us/library/system.io.binaryreader%28v=vs.110%29.aspx[^].

—SA

Posted 11-Feb-15 11:21am

Sergey Alexandrovich Kryukov

Updated 11-Feb-15 13:24pm

v2

Comments

Golden Basim 11-Feb-15 17:39pm

how can i use (using) in more than scope ?

if ( .... )
{
using (FileStream stream = new FileStream( /* ... */ )) {
// use stream object here
}

if(.....)
{

// Dispose

}
}

Sergey Alexandrovich Kryukov 11-Feb-15 19:22pm

And what's the problem? Just read about "using". This is the same kind of statement and any other block statement...
—SA

Golden Basim 11-Feb-15 18:00pm

the same error :

using (FileStream fileStream_1 = new FileStream(JCM_File_Path_01, FileMode.Open, FileAccess.Read, FileShare.Read))
{

if (Startdate2 == JCM_NOW2)
{
if (checkBox1.Checked == true)
{
try
{
fileStream_1 = null;
System.Diagnostics.Process.Start(System.Convert.ToString(row.Cells["Lec_media"].Value));
}
finally
{
if (fileStream_1 != null)
fileStream_1.Close();
}
}

}

if (Enddate2 == JCM_NOW2)
{
// if (fileStream_1 != null) ((IDisposable)fileStream_1).Dispose();
fileStream_1.Close();

// this code does not close the file which opened above .. why?

}
}

Andreas Gieriet 11-Feb-15 18:23pm

You seem not to understand several parts of the solution.
1) The using construct *does* call Dispose on the instance (this is the only purpose of using!).
2) Dispose closes the stream (see the online documentation).
Andi

Sergey Alexandrovich Kryukov 11-Feb-15 19:23pm

Exactly.
—SA

Sergey Alexandrovich Kryukov 11-Feb-15 19:22pm

What error, for goodness sake? Just write it all correctly. Act from first principles, not through guesswork.
—SA

Andreas Gieriet 11-Feb-15 18:24pm

My 5!
Cheers
Andi

Sergey Alexandrovich Kryukov 11-Feb-15 19:23pm

Thank you, Andi.
—SA

Golden Basim 11-Feb-15 19:25pm

Dispose closes the stream not file ?

thats mean that the file still open ?

Sergey Alexandrovich Kryukov 11-Feb-15 19:52pm

You dispose the stream object, that's it. No, it will close the file. It closes the stream according to the nature of runtime type of a stream. Do you understand OOP? This is what it is...
—SA

Andreas Gieriet 11-Feb-15 20:24pm

Please, please read the documentation! There is plenty of examples: FileStream. Especially see the documentation on Dispose: [...] This method disposes the stream, by writing any changes to the backing store and closing the stream to release resources. [...]
Andi

Sergey Alexandrovich Kryukov 11-Feb-15 20:26pm

Exactly.
—SA

Golden Basim 11-Feb-15 20:16pm

how i can close file too ?

Sergey Alexandrovich Kryukov 11-Feb-15 20:22pm

Closing the file is the same when you close certain stream (file-related stream). Streams are abstractions which are implemented on top of different OS entities, files in particular. Again: do you understand OOP? This is what it is...
—SA

Golden Basim 12-Feb-15 8:23am

something