C# in Depth

Namespace aliases195Listing 7.6using System;using WinForms = System.Windows.Forms;using WebForms = System.Web.UI.WebControls;class WinForms{}class Test{static void Main(){Console.WriteLine (typeof (WinForms::Button));Console.WriteLine (typeof (WebForms::Button));}}Instead of WinForms.Button, listing 7.6 uses WinForms::Button, and the compiler ishappy. If you change the :: back to . you’ll get a compilation error. So, if you use ::everywhere you use an alias, you’ll be fine, right? Well, not quite…7.4.2 The global namespace aliasUsing :: to tell the compiler to use aliasesThere’s one part of the namespace hierarchy that you can’t define your own alias for:the root of it, or the global namespace. Suppose you have two classes, both namedConfiguration; one is within a namespace of MyCompany and the other doesn’t havea namespace specified at all. Now, how can you refer to the “root” Configurationclass from within the MyCompany namespace? You can’t use a normal alias, and if youjust specify Configuration the compiler will use MyCompany.Configuration.In C# 1, there was simply no way of getting around this. Again, C# 2 comes to therescue, allowing you to use global::Configuration to tell the compiler exactly whatyou want. Listing 7.7 demonstrates both the problem and the solution.Listing 7.7Use of the global namespace alias to specify the desired type exactlyusing System;class Configuration {}namespace Chapter7{class Configuration {}}class Test{static void Main(){Console.WriteLine(typeof(Configuration));Console.WriteLine(typeof(global::Configuration));Console.WriteLine(typeof(global::Chapter7.Test));}}Licensed to Rhona Hadida