What is a namespace in C#

In C#, namespace (Namespace) is a way to organize a large number of classes, structures, enumerations, interfaces, delegates, and other namespaces together, which helps to avoid naming conflicts and facilitates code organization and manage.

In the .NET Framework, namespaces are organized in a hierarchical fashion. For example, System.Collections.Generica namespace represents such a hierarchical structure: the top level is Systema namespace, which contains a Collectionssub-namespace named , which Collectionsin turn contains a sub-namespace Genericnamed . In Genericthe namespace, we can find commonly used collection classes such as List<T>, and so on.Dictionary<TKey, TValue>

In C# code, we use usingkeywords to introduce namespaces, so that the types in the namespace can be used directly in the file without fully qualified names. for example:

using System;
using System.Collections.Generic;

public class Example
{
    
    
    public void PrintNumbers(List<int> numbers)
    {
    
    
        foreach (var number in numbers)
        {
    
    
            Console.WriteLine(number);
        }
    }
}

In this example, we introduced Systemand System.Collections.Generictwo namespaces, so we can directly use Consoleand List<T>these two types without writing System.Consoleand System.Collections.Generic.List<T>.