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
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