C# 命名空间别名 - 有什么意义?

问题描述

人们会在何时何地使用命名空间别名

Where or when would one would use namespace aliasing like

 using someOtherName =  System.Timers.Timer;

在我看来，这只会增加理解语言的困惑.

It seems to me that it would just add more confusion to understanding the language.

推荐答案

那是类型别名，不是命名空间别名；消除歧义很有用 - 例如，反对:

That is a type alias, not a namespace alias; it is useful to disambiguate - for example, against:

using WinformTimer = System.Windows.Forms.Timer;
using ThreadingTimer = System.Threading.Timer;

(ps: 感谢您选择Timer ;-p)

(ps: thanks for the choice of Timer ;-p)

否则，如果您在同一个文件中同时使用 System.Windows.Forms.Timer 和 System.Timers.Timer，则必须继续提供全名(因为 Timer 可能会令人困惑).

Otherwise, if you use both System.Windows.Forms.Timer and System.Timers.Timer in the same file you'd have to keep giving the full names (since Timer could be confusing).

它还与 extern 别名一起使用，用于使用来自不同程序集的具有相同完全限定类型名称的类型 - 很少见，但受支持很有用.

It also plays a part with extern aliases for using types with the same fully-qualified type name from different assemblies - rare, but useful to be supported.

实际上，我可以看到另一种用途:当您想要快速访问一个类型，但又不想使用常规的 using 因为您无法导入一些冲突的扩展方法时......有点复杂，但是……这里有一个例子……

Actually, I can see another use: when you want quick access to a type, but don't want to use a regular using because you can't import some conflicting extension methods... a bit convoluted, but... here's an example...

namespace RealCode {
    //using Foo; // can't use this - it breaks DoSomething
    using Handy = Foo.Handy;
    using Bar;
    static class Program {
        static void Main() {
            Handy h = new Handy(); // prove available
            string test = "abc";            
            test.DoSomething(); // prove available
        }
    }
}
namespace Foo {
    static class TypeOne {
        public static void DoSomething(this string value) { }
    }
    class Handy {}
}
namespace Bar {
    static class TypeTwo {
        public static void DoSomething(this string value) { }
    }
}

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