问题
I read this MSDN like about it and ran its example. http://msdn.microsoft.com/en-us/library/system.net.httpwebrequest.useragent.aspx
when I change the uSerAgnet to something like "blah", the output is wrong but when I use the same thing that is in the example of even when I comment out the line of code that is setting the UserASgent, the output is correct.
what is UserAgent at all ? when should I set it ? How to know to what value should I set it ?
thanks
回答1:
The User Agent is used to identify the client and operating system etc. It's most commonly used in browsers. You can used the User Agent to specify who you are, and the web server can return a Response with data appropriate for you client. For instance my User Agent I used to access this site is: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_3; en-US) AppleWebKit/533.4 (KHTML, like Gecko) Chrome/5.0.375.70 Safari/533.4 Had I instead been a web crawler I would have used something else, something the web server would identify as a crawler, and the web server (the web developer) could have return a optimized page for indexing.
Unless you really need to, I would advice against coming up with you own User Agent, lack of standardization is a big enough issue in this field.
Are there any reason in particular you need to mess with the User Agent?
This page contain a list of many known User Agents.
来源：https://stackoverflow.com/questions/3057328/httpwebrequest-useragent-what-does-it-do