Question

Please looking in the below codes:

new StreamWriter("c:/myText.txt").Write("Some thing...");

And,

using (var streamWriter = new StreamWriter("c:/myText.txt")
{
    streamWriter.Write("Some thing...");
}

The first code creating the file but doesn’t write “Some thing…” in that.
But the second code works as well and write in that.

Why this issue happens? What is the difference?

Answer 1

The StreamWriter class implements IDisposable which means that it holds a resource that need to be released or it has some clean up code that needs to be run before the object is garbage collected.

In this case calling Dispose closes the stream, potentially writing the last data to the stream before doing so.

By coding new StreamWriter("c:/myText.txt").Write("Some thing..."); you don’t retain a reference to the stream and therefore have no way to call Dispose to properly close the stream.

Remember, the Garbage Collector never calls dispose for you. You must explicitly do so.

The second block of code uses the using statement which will automatically call Dispose when the block is exited. This is the correct way to write this code.