How to use :: Namespace Alias Qualifier in C#

Last Updated : 06 Mar, 2019

Namespace Alias Qualifier(::) makes the use of alias name in place of longer namespace and it provides a way to avoid ambiguous definitions of the classes. It is always positioned between two identifiers. The qualifier looks like two colons(::) with an alias name and the class name. It can be global. Thus it doesn’t invoke a lookup in the aliased namespace but in the global namespace.

Syntax:

alias_name::class-name;

Example:

   // C# program to illustrate how to use 
// the :: Namespace Alias Qualifier 
using System; 
  
// creating aliased name 
using first = firstnamespace; 
using sec = secondnamespace; 
  
namespace Geeks { 
  
class GFG { 
  
    // Main Method 
    static void Main() 
    { 
  
        // use of Namespace alias qualifier(::) 
        first::GFG1 obj1 = new first::GFG1();  
        obj1.display(); 
    } 
} 
} 
  
// Both namespaces have a  
// class named GFG1 
namespace firstnamespace { 
  
class GFG1 { 
  
    public void display() 
    { 
        Console.WriteLine("It is the first namespace."); 
    } 
} 
} 
  
namespace secondnamespace { 
  
class GFG1 { 
  
    public void display() 
    { 
        Console.WriteLine("It is the second namespace."); 
    } 
} 
} 
 
  

Output:

  It is the first namespace.

Note: The namespace alias qualifier :: is only used for the namespaces or aliases and cannot be used for subclasses.

Example:

  System.Collections::lists obj= new System.Collections.lists() // illegal  aliasname = System.Collections;  aliasname::lists obj = new aliasname::lists(); // Legal

   // C# program to illustrate how to use 
// the :: Namespace Alias Qualifier 
using aliasname = System.Collections; 
  
namespace Geeks { 
  
class GFG { 
  
    // Main Method 
    static void Main() 
    { 
        // using :: Namespace Alias Qualifier 
        aliasname::Hashtable obj = new aliasname::Hashtable(); 
  
        // Add items to the table. 
        obj.Add("ASCII value of A is:", "65"); 
        obj.Add("ASCII value of B is:", "66"); 
  
        // displaying the result 
        foreach(string i in obj.Keys) 
        { 
            System.Console.WriteLine(i + " " + obj[i]); 
        } 
    } 
} 
} 
 
  

Output:

  ASCII value of A is: 65  ASCII value of B is: 66

How to Create and Use Alias Command in Linux

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