Why do static methods need to be wrapped into a class?

问题

Sorry for the unlearned nature of this question. If there's a simple answer, just a link to an explanation will make me more than happy.

After 6 months programming I find static classes to be somewhat useful for storing routines that apply to many different classes. Here's a simplified example of how I use static classes, it's a class for parsing text into various things

public static class TextProcessor 
{
    public static string[] GetWords(string sentence)
    {
        return sentence.Split(' '); 
    }

    public static int CountLetters(string sentence)
    {
        return sentence.Length; 
    }

    public static int CountWords(string sentence)
    {
        return GetWords(sentence).Length; 
    }
}

And I use this in obvious ways like

    class Program
{
    static void Main(string[] args)
    {
        string mysentence = "hello there stackoverflow.";
        Console.WriteLine("mysentence has {0} words in it, fascinating huh??", TextProcessor.CountWords(mysentence)); 

        Console.ReadLine(); 
    }
}

My question is: Why is it necessary to wrap these static methods in a static class? It seems to serve no purpose. Is there a way I can have these methods on their own not wrapped in a class? I know encapsulation is beneficial but I don't see the use for static methods wrapped in static class. Is there something I am missing stylistically or otherwise? Am I completely barking up a silly tree? Am I thinking too much?

回答1:

In C#, any method has to be declared inside a class. That's just how the language is specified.

A static class is actually more akin to a module than a class, so I too think you should be able to either:

define a function outside a class or;
import a module the same way you import a namespace (with using)

VB.NET, F# and Nemerle actually allow you to declare modules and import them; what allows you to use their methods unqualified.

This is valid Nemerle:

using System.Console; // import static methods in the Console class
class Hello {
  static Main() : void {
    WriteLine("Hello, world!"); // unqualified access!
  }
}

Also, take a look at extension methods, they might allow you to "solve" this in a different way. The methods in your TextProcessor are begging to be string extension methods.

回答2:

This post by eric lippert gives a pretty detailed explanation. I'm not sure if this guy "eric" knows what he's talking about or not though ;-)

回答3:

It would be somewhat awkward to have methods just dangling around in a random namespace.

I suspect the answer is to provide "scope". Just because a method is static, doesn't mean it doesn't have a scope. It can still access other static private methods or member variables - and the class provides a "home" for these things to live in.

Static classes can also have static constructors that get called the first time a static method is used, so this provides the ability to set stuff up as needed.

It's more of an organizational design than anything to due with technical limitations.

回答4:

already there are many threads on this topic which have enough information... you can find one here..

回答5:

A static method is a method called in a single instance of a class that is created at run-time.

来源：https://stackoverflow.com/questions/8131546/why-do-static-methods-need-to-be-wrapped-into-a-class

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static-methods