There may be several solutions, because the action of creating a POST request and sending it to the server is separate from the act of parsing and executing JavaScript.
However, if you want to create a POST request, there are several options in .NET, the most notable of which is HttpWebRequest / HttpWebResponse , as well as WebClient , which is a higher-level wrapper around HttpWebRequest / HttpWebResponse .
To run JavaScript, the assumption is that you want to execute JavaScript on the page, and while there are standalone XML parsers / development mechanisms , they do not necessarily work on the page.
For this purpose, the MSHTML library (although you said that you do not want to use it, I assume that you are on the server and have problems with streams / COM apartments?) Is a really good choice, and you can wrap access to it enough in .NET (although not easy, depending on your needs) so that you can do what you want.
If you are a fan of WebKit , you can use . NET shell for WebKit (WebKit.NET) in your application. Note: There are some issues as of September 2011 that may or may not be addressed so far.