C# namespace using Directive
In this chapter you will learn:
- What is namespace using Directive
- Example for C# namespace using Directive
- using statement and namespace
- Namespaces prevent name conflicts
Description
The using directive imports a namespace.
Example
This is a convenient way to refer to types without their fully qualified names.
For example suppose we have the following class definition with namespace;
//from w w w. j av a 2 s . c o m
namespace Outer
{
namespace Middle
{
namespace Inner
{
class Class1 {}
class Class2 {}
}
}
}
Here is the way to use using directive to reference types inside
using Outer.Middle.Inner; //w w w .j ava 2 s .c om
class Test
{
static void Main()
{
Class1 c;
}
}
Example 2
C# uses using statement to import namespace.
Once a namespace is imported we can use its types with simple name(class name).
using System;//from w ww . j av a 2 s . c om
using A.B.C;
namespace A
{
namespace B
{
namespace C
{
class MyClass
{
}
}
}
}
class Program
{
static void Main(string[] args)
{
MyClass cls = new MyClass();
}
}
The code above generates the following result.
Example 3
using System; /* ww w. j a v a 2 s . c o m*/
namespace Counter {
class MyClass {
public MyClass(){
Console.WriteLine("Counter1 namespace.");
}
}
}
namespace Counter2 {
class MyClass {
public MyClass() {
Console.WriteLine("Counter2 namespace.");
}
}
}
class MainClass {
public static void Main() {
// This is CountDown in the Counter namespace.
Counter.MyClass m1 = new Counter.MyClass();
// This is CountDown in the default namespace.
Counter2.MyClass m2 = new Counter2.MyClass();
}
}
The code above generates the following result.
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What you will learn in the next chapter: