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Nickname qualifier

Handbook C# · Practical Guide

Refers to a namespace via a global or specified alias. extern alias can distinguish types of the same name in different assemblies.

Simple example (Example.cs)

Save this example separately as Example.cs. Run it independently of the other examples on this page.

Example.cs:

// PROJECT-EXAMPLE
global::System.Console.WriteLine("Ready");

Result:

Ready

Syntax

global::Namespace.Type / alias::Type

Example 1

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
using System.IO;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;

public static class Program
{
    public static async Task Main(string[] args)
    {
        global::System.Console.WriteLine(typeof(global::System.String).Name);
    }
}

Example 2

using Core = System;
public static class Program { public static void Main() { Core::Console.WriteLine(Core::Math.Abs(-4)); } }

Official source: Microsoft Learn.