&是什么QUOT;本"作为方法参数的前缀使用时，是什么意思？ [英] What does "this" mean when used as a prefix for method parameters?

问题描述

我敢肯定，答案是显而易见的东西，而我有点不好意思，我真的不知道答案了，但考虑下面的代码示例我拿起在阅读专业ASP.NET MVC 1.0

I'm sure the answer is something obvious, and I'm kind of embarrassed that I don't really know the answer already, but consider the following code sample I picked up while reading "Professional ASP.NET MVC 1.0":

public static class ControllerHelpers
{
    public static void AddRuleViolations(this ModelStateDictionary modelState, IEnumerable<RuleViolation> errors)
    {
        foreach (RuleViolation issue in errors)
            modelState.AddModelError(issue.PropertyName, issue.ErrorMessage);
    }
}

我明白这是什么静态方法是干什么的，但什么我不明白的是本是在方法签名服务的目的是什么字。任何人都可以告诉我吗？

I understand what this static method is doing, but what I don't understand is what purpose the word "this" is serving in the method signature. Can anyone enlighten me?

推荐答案

这是一个新的名为C＃3.0功能的扩展方法。

That is a new C# 3.0 feature called extension method.

这意味着，您添加一个新的方法你ModelStateDictionary对象。你可以把它像一个正常的方法：

It means, that you add a new method to your ModelStateDictionary objects. You can call it like a normal method:

yourModelStateDictionary.AddRuleViolations( errors );

请参阅，第一个参数（即this'参数）被跳过。它赋予只是ModelStateDictionary为您的扩展方法的有效目标

See, that the first parameter (the 'this'-parameter) is skipped. It assigns just ModelStateDictionary as a valid target for your extension method.

线索是，你可以用任何类做到这一点 - 即使封存或第三方类，等等。 .Net框架类（例如在对象或字符串）。

The clue is, that you can do this with any class - even sealed or 3rd party classes, like .Net framework classes (for instance on object or string).

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