C Sharp Programming/Keywords/using

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The using keyword has two completely unrelated meanings in C#, depending on if it is used as a directive or a statement.

[edit] The directive

using as a directive resolves unqualified type references so a developer doesn't have to specify the complete namespace.

Example:

using System;

// A developer can now type Console.WriteLine(); rather than System.Console.WriteLine().

using can also provide a namespace alias for referencing types.

Example:

using Utils = Company.Application.Utilities;

[edit] The statement

using as a statement automatically calls the Dispose() on the specified object. The object must implement the IDisposable interface.

Example:

using (System.IO.StreamReader reader = new StreamReader("readme.txt"))
{
  // read from the file
}

// readme.txt has now been closed automatically.

C# Keywords
abstract as base bool break byte case catch char checked class const continue decimal default delegate do double else enum event explicit extern false finally fixed float for foreach goto if implicit in int interface internal is lock long namespace new null object operator out override params private protected public readonly ref return sbyte sealed short sizeof stackalloc static string struct switch this throw true try typeof uint ulong unchecked unsafe ushort using var virtual void volatile while
Special C# Identifiers
add alias get global partial remove set value where yield