use of “using” keyword in c# [duplicate]

Answer 1

Two uses:

• Using directives, e.g.

  using System;
  using System.IO;
  using WinForms = global::System.Windows.Forms;
  using WinButton = WinForms::Button;
  

  These are used to import namespaces (or create aliases for namespaces or types). These go at the top of the file, before any declarations.

• Using statements e.g.

  using (Stream input = File.OpenRead(filename))
  {
      ...
  }
  

  This can only be used with types that implement IDisposable, and is syntactic sugar for a try/finally block which calls Dispose in the finally block. This is used to simplify resource management.