Using keyword Usage summary in C #

The Using keyword in C # has two main uses:

1. Using as directive:

(1) used to introduce namespaces into the current unit, for example: using System.Windows.Forms;

(2) Create an alias for the existing namespace, for example: using Form = System.Windows.Forms;

2. Using as statement: Defines a code block scope that frees resources at the end of the code block.

(1) Declare an object before the using statement:

1 New Class (); 2 using (C1) 3 {4     // Use C1 5 }

(2) Declaring an object in a using statement, which must be declared inside a using statement when more than one object is to be used:

1 using New New Class ()) 2 {3     // Use c1, C2 4 }

During the program compilation phase, the compiler automatically builds the using statement into a try-catch-finally statement and calls the object's Dispose method in the finally block to clean up the resource.

Using keyword Usage summary in C #