C＃中的HttpWebRequest的WebRequest VS [英] C# HttpWebRequest vs WebRequest

问题描述

我看到这片code的：

I saw this piece of code:

var request = (HttpWebRequest) WebRequest.Create("http://www.google.com");

为什么需要投（HttpWebRequest的）？为什么不使用 HttpWebRequest.Create ？又为何 HttpWebRequest.Create 作的WebRequest ，而不是的HttpWebRequest ？

Why do you need to cast (HttpWebRequest)? Why not just use HttpWebRequest.Create? And why does HttpWebRequest.Create make a WebRequest, not a HttpWebRequest?

推荐答案

的创建方法是静态的，只存在于的WebRequest 。调用它作为 HttpWebRequest.Create 可能看起来不同，但实际上它编译成叫 WebRequest.Create 。它只是似乎是的HttpWebRequest 因为继承。

The Create method is static, and exists only on WebRequest. Calling it as HttpWebRequest.Create might look different, but its actually compiled down to calling WebRequest.Create. It only appears to be on HttpWebRequest because of inheritance.

的创建方法在内部，使用工厂模式做实际创建对象的基础上，乌里你传递给它。实际上，你可以找回其他的对象，如的FtpWebRequest 或 FileWebRequest ，这取决于乌里。

The Create method internally, uses the factory pattern to do the actual creation of objects, based on the Uri you pass in to it. You could actually get back other objects, like a FtpWebRequest or FileWebRequest, depending on the Uri.

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