using directive meaning

Using directives function:

is to import namespaces so that you can use the StringBuilder class instead of System.Text.StringBuilder builder = new System.Text.StringBuilder (),

Ease of operation, enhanced readability.

Some instructions have the following meanings:

http://www.zybang.com/question/8ae2157cf831e325c6ceed8650f0045e.html?fr=iks&word=using+ System.configuration%3b&ie=gbk

The
1. using System; The primary namespace, which contains all. NET base types and common types, such as object, such as String, and so on
2. using System.Collections; Contains commonly used collection classes such as ArrayList
3. using System.Configuration; configuration namespaces containing application configuration-related analogies such as ConfigurationManager
4. using System.Data; The data namespace, which contains the most basic types of ADO, such as the
5. using System.Linq, such as DbConnection, 3.5, the LINQ syntax introduced needs to provide the support class, mainly includes the enumerable extension method support class
6. using System.Web; The core namespace required by ASP, including the underlying run environment class
7. using System.Web.Security, such as httpruntime; ASP. NET in the role verification and security aspects of the class library, the more important is FormsAuthentication
8. using System.Web.UI; ASP. NET Web page control requires a basic namespace, Contains all
9. using System.Web.UI.HtmlControls such as control or important ipostbackeventhandler interfaces; HTML native controls, such as input runat= The server maps to one of the Inputxxx control classes in this polygon
10. using System.Web.UI.WebControls; System.Web.UI.WebControls.WebParts; The space required for WebParts technology, but seldom with the
11. using System.Xml.Linq; Linq2xml's primary namespace, which contains XDocument and XElement, the more important class
12. using System.Data, introducing a data manipulation namespace that can be used such as the DataSet DataSet class

using directive meaning