Wrote the most user-friendly look here: https://www.jb51.net/article/177025.htm
Note that there are actually three kinds of writing three different application scenarios, no need to pursue the latest wording, pay attention to understand the differences and use, learn and use.
Please find details on MSDN, pay attention to check the documentation of methods, sample a lot of code that need to click on to deeper parts.
Code updates the WebClient, the next put himself deployed a file server on the local IIS.
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