The scope of C#'s using keyword

Question

I understand that any time I am instantiating a class that implements IDisposable, I should use the using keyword in order to ensure that it's disposed of properly.

Like so:

using (SecureString s = new SecureString())
{

}

The above is easy for me to understand - I can use s however I want within those brackets, but once I leave those brackets, I can no longer refer to s. The scope is easy to see.

But what I don't understand is how it works when you use using with no enclosing brackets.

private void Function()
{
    // Some code here

    using (SecureString s = new SecureString())

    // more code here
}

You aren't required to use brackets at all... so... how do I know where I am able to use the object and where it gets disposed, if there are no brackets to go with the using keyword?

Answer 1

In almost every case in C# when you have the choice of using braces you can substitute them with a single line of code.

Consider an if statement:

if (someBool)
    DoSomething();
else
    DoSomethingElse();

That is just as valid as the following:

if (someBool)
{
    // do lots of things
}
else
    DoSomethingElse();

This is probably almost universally true for any time you can use the { and } brackets.

The nice thing about this with the using statement is that you can nest them like this:

using (var stream = new NetworkStream(...))
using (var sslStream = new SslStream(stream))
using (var reader = new StreamReader(sslStream))
{
    reader.WriteLine(...);
}

This is equivalent to the following:

using (var stream = new NetworkStream(...))
{
    using (var sslStream = new SslStream(stream))
    {
        using (var reader = new StreamReader(sslStream))
        {
            reader.WriteLine(...);
        }
    }
}

Although I think you'd agree it's much nicer looking.