Statements - Illustrated C# 2005 - page 234

Example of the using Statement
The following code uses the using statement twice—once with a class called TextWriter , and
once with a class called TextReader , both from the System.IO namespace. Both classes imple-
ment the IDisposable interface, as required by the using statement.

￿The TextWriter resource opens a text file for writing and writes a line to the file.

￿The TextReader resource then opens the same text file, and reads and displays the con-
tents, line by line.

In both cases, the using statement makes sure that the objects' Dispose methods
are called.

￿

￿ Notice also the difference between the using statements in Main and the using directives

on the first two lines.

using System; // using DIRECTIVE; not using statement
using System.IO; // using DIRECTIVE; not using statement

namespace UsingStatement
{
class Program
{
static void Main( )
{
// using statement
using (TextWriter tw = File.CreateText("Lincoln.txt") )
{
tw.WriteLine("Four score and seven years ago, ...");
}

// using statement
using (TextReader tr = File.OpenText("Lincoln.txt"))
{
string InputString;
while (null != (InputString = tr.ReadLine()))
Console.WriteLine(InputString);
}
}
}
}

This code produces the following output:

Four score and seven years ago, ...