Question

I am writing following code.

        static void Main(string[] args)
        {
             FileInfo fiobj = new FileInfo(@"e:\mohan.txt");
             Console.Write("Name of file:"+ fiobj.Name);

             using(StreamWriter sw = fiobj.AppendText())
             {
                sw.WriteLine("mohan!");
             }
        }

    // code not working

    static void Main(string[] args)
        {
           FileInfo fiobj = new FileInfo(@"e:\mohan.txt");
           Console.Write("Name of file:"+ fiobj.Name);

           StreamWriter sw = fiobj.AppendText();            
           sw.WriteLine("mohan!");            
        }

When I use the “using(){}” block I am able to write into file but when I wrote the same code without using(){} block I am not able to do So.
Why is So?
As far as I know using(){} block specifies the scope of the object for it’s life time.
Does using(){} block doing something fancy here to make it enable to write the data to file.

Answer 1

The using is shorthand for correctly ensuring that your object is Disposed correctly once the scope falls outside of the using block.

Your code is equivalent to:

StreamWriter sw = fiobj.AppendText();
try
{
    sw.WriteLine("mohan!");
}
finally
{
    if (sw != null)
    {
        ((IDisposable)sw).Dispose();
    }
}

This code correctly closed and disposes of the StreamWriter. Without it, it would remain locked.

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