Using Statement

Techopedia explains Using Statement

The .NET framework is designed with an automatic memory management feature by which memory allocated to an object is released in non-deterministic mode whenever the Common Language Runtime decides to perform garbage collection (GC). However, unmanaged resources like file handles, network connections, etc., have to be released as quickly as possible. The using statement allows the developer to specify the instant at which such limited resources are to be released.

The using statement takes one parameter, a resource that is represented by a class or struct that implements the System.IDisposable interface. The only method that needs to be implemented through the interface is "Dispose," which can include the code necessary for cleaning up the resource. If this method is not called, the GC takes care of the disposal automatically.
For example, the using statement can be used to open a file stream by creating an object of System.IO.FileStream type, which can be used within the scope of the code block of the using statement.

The C# compiler translates the code for the using statement into three sections in Microsoft Intermediate Language:

• Acquisition of the resource within the section for memory allocation of the resource
• Use of the resource enclosed within a "try" block
• Disposal of the resource by releasing it (calling the "Dispose" method of the resource object) within the "finally" block

The using statement does not allow the resource object to be modified or reassigned within the block in which it is used.
This definition was written in the context of C#.