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==Creates a namespace with a single class==

<source lang="csharp">using System;
namespace StringSwitch
{
class MySwitch
{
}
}
////////////////////////////////////////////
using System;
using StringSwitch;
class MainClass
{
public static void Main()
{
string localString;
MySwitch s = new MySwitch();
}
}</source>

==Declare a namespace==

<source lang="csharp">namespace Counter {
class MyClass {
}
}</source>

==Demonstrate a namespace.==

<source lang="csharp">using System;

namespace Counter {
class MyClass {
}
}

class MainClass {
public static void Main() {
Counter.MyClass my = new Counter.MyClass();
}
}</source>

==Demonstrate the :: qualifier.==

<source lang="csharp">using System;

using Counter;
using AnotherCounter;

// Give Counter an alias called Ctr.
using Ctr = Counter;

namespace Counter {
class MyClass {
}
}

namespace AnotherCounter {
class MyClass {
}
}

class MainClass {
public static void Main() {

Ctr::MyClass m = new Ctr::MyClass();
}
}</source>

==Full qualify name==

For example, the line

<source lang="csharp">Console.WriteLine("A simple C# program.");</source>

==Namespace Introduction==

<OL><LI>The namespace provides a way to keep one set of names separate from another.</LI><LI>Names declared in one namespace will not conflict with the same names declared in another.</LI><LI>The namespace System is reserved for items in the .NET Framework class library.</LI><LI>The using keyword simply states that the program is using the names in the given namespace.</LI></OL>
1.5.Namespace
1.5.1.
Namespace Introduction
1.5.2.
<A href="/Tutorial/CSharp/0020__Language-Basics/Fullqualifyname.htm">Full qualify name</a>
1.5.3.
<A href="/Tutorial/CSharp/0020__Language-Basics/Simplestnamespacewithclassdefinition.htm">Simplest namespace with class definition</a>
1.5.4.
<A href="/Tutorial/CSharp/0020__Language-Basics/Declareanamespace.htm">Declare a namespace</a>
1.5.5.
<A href="/Tutorial/CSharp/0020__Language-Basics/Demonstrateanamespace.htm">Demonstrate a namespace.</a>
1.5.6.
<A href="/Tutorial/CSharp/0020__Language-Basics/Usefullyqualifiedclassname.htm">Use fully qualified class name</a>
1.5.7.
<A href="/Tutorial/CSharp/0020__Language-Basics/TwolevelsofNamespaces.htm">Two levels of Namespaces</a>
1.5.8.
<A href="/Tutorial/CSharp/0020__Language-Basics/Namespacewithdot.htm">Namespace with dot</a>
1.5.9.
<A href="/Tutorial/CSharp/0020__Language-Basics/Renamethenamespaces.htm">Rename the namespaces</a>
1.5.10.
<A href="/Tutorial/CSharp/0020__Language-Basics/Namespacespreventnameconflicts.htm">Namespaces prevent name conflicts</a>
1.5.11.
<A href="/Tutorial/CSharp/0020__Language-Basics/Namespacesareadditive.htm">Namespaces are additive.</a>
1.5.12.
<A href="/Tutorial/CSharp/0020__Language-Basics/Namespacescanbenested.htm">Namespaces can be nested</a>
1.5.13.
<A href="/Tutorial/CSharp/0020__Language-Basics/Demonstratethequalifier.htm">Demonstrate the :: qualifier.</a>
1.5.14.
<A href="/Tutorial/CSharp/0020__Language-Basics/Theuseoftwonamespaces.htm">The use of two namespaces</a>
1.5.15.
<A href="/Tutorial/CSharp/0020__Language-Basics/Theuseofnamespacehierarchies.htm">The use of namespace hierarchies</a>
1.5.16.
<A href="/Tutorial/CSharp/0020__Language-Basics/Createsanamespacewithasingleclass.htm">Creates a namespace with a single class</a>
1.5.17.
<A href="/Tutorial/CSharp/0020__Language-Basics/SameclassnameunderdifferentNamespaces.htm">Same class name under different Namespaces</a>

==Namespaces are additive.==

<source lang="csharp">using System;

using Counter;

namespace Counter {
class MyClass {
}
}

namespace Counter {
class MySecondClass {
}
}

class MainClass {
public static void Main() {
MyClass m = new MyClass();
MySecondClass cu = new MySecondClass();
}
}</source>

==Namespaces can be nested==

<source lang="csharp">using System;

namespace NS1 {
class ClassA {
public ClassA() {
Console.WriteLine("constructing ClassA");
}
}
namespace NS2 { // a nested namespace
class ClassB {
public ClassB() {
Console.WriteLine("constructing ClassB");
}
}
}
}

class MainClass {
public static void Main() {
NS1.ClassA a = new NS1.ClassA();

NS1.NS2.ClassB b = new NS1.NS2.ClassB();
}
}</source>
<pre class=codeResult>constructing ClassA
constructing ClassB</pre>

==Namespaces prevent name conflicts==

<source lang="csharp">using System;

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();

}
}</source>
<pre class=codeResult>Counter1 namespace.
Counter2 namespace.</pre>

==Namespace with dot==

<source lang="csharp">namespace Outer.Inner
{
class MyClass
{
public static void Function() {}
}
}</source>

==Rename the namespaces==

<source lang="csharp">using ThatConsoleClass = System.Console;
class MainClass
{
public static void Main()
{
ThatConsoleClass.WriteLine("Hello");
}
}</source>
<pre class=codeResult>Hello</pre>

==Same class name under different Namespaces==

<source lang="csharp">using System;
namespace Foo {
public class Money {
public Money() {
}
public void Print( ) {
Console.WriteLine("Foo.Money.Print");
}
}
}
namespace Bar {
public class Money {
public Money( ) {
}
public void Print( ) {
Console.WriteLine("Bar.Money.Print");
}
}
}

public class MainClass {
public static void Main( ) {
Foo.Money fm = new Foo.Money();
Bar.Money bm = new Bar.Money();
fm.Print( );
bm.Print( );
}
}</source>
<pre class=codeResult>Foo.Money.Print
Bar.Money.Print</pre>

==Simplest namespace with class definition==

A namespace is declared using the namespace keyword.
The general form of namespace is shown here:

<source lang="csharp">namespace name {
// members
}</source>

==The use of namespace hierarchies==

<source lang="csharp">namespace CompanyName
{
namespace UserInterface // nested namespace
{
public class MyClass
{
public void Test()
{
System.Console.WriteLine("UserInterface Test()");
}
}
}
}

namespace CompanyName.DatabaseAccess // nested namespace using dot
{
public class MyClass
{
public void Test()
{
System.Console.WriteLine("DatabaseAccess Test()");
}
}
}

class MainClass {
public static void Main() {
CompanyName.UserInterface.MyClass myUI = new CompanyName.UserInterface.MyClass();
CompanyName.DatabaseAccess.MyClass myDB = new CompanyName.DatabaseAccess.MyClass();
CompanyName.DatabaseAccess.MyClass myMT = new CompanyName.DatabaseAccess.MyClass();
myUI.Test();
myDB.Test();
myMT.Test();
}
}</source>
<pre class=codeResult>UserInterface Test()
DatabaseAccess Test()
DatabaseAccess Test()</pre>

==The use of two namespaces==

<source lang="csharp">namespace CompanyName
{
public class Car
{
public string make;
}
}
namespace DifferentCompany
{
public class Car
{
public string make;
}
}
class MainClass
{
public static void Main()
{
System.Console.WriteLine("Creating a CompanyName.Car object");
CompanyName.Car myCar = new CompanyName.Car();
myCar.make = "Toyota";
System.Console.WriteLine("myCar.make = " + myCar.make);
System.Console.WriteLine("Creating a DifferentCompany.Car object");
DifferentCompany.Car myOtherCar = new DifferentCompany.Car();
myOtherCar.make = "Porsche";
System.Console.WriteLine("myOtherCar.make = " + myOtherCar.make);
}
}</source>
<pre class=codeResult>Creating a CompanyName.Car object
myCar.make = Toyota
Creating a DifferentCompany.Car object
myOtherCar.make = Porsche</pre>

==Two levels of Namespaces==

<source lang="csharp">namespace Outer
{
namespace Inner
{
class MyClass
{
public static void Function() {}
}
}
}</source>

==Use fully qualified class name==

<source lang="csharp">class Example {

public static void Main() {

// Console.WriteLine is fully qualified.
System.Console.WriteLine("A simple C# program.");
}
}</source>
<pre class=codeResult>A simple C# program.</pre>

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