DotNetBrowser

To load web page by its URL and send some POST data, use the Browser.LoadURL(LoadURLParams params) method. The following code demonstrates how to load URL and send POST data in different formats using extra headers:

application/x-www-form-urlencoded

browser.LoadURL(new LoadURLParams("http://www.google.com", 
            "myKey=myValue&myKey2=myValue2"));

text/plain

browser.LoadURL(new LoadURLParams("http://www.google.com", 
            "Some Text...", "Content-Type: text/plain\n"));

application/json

browser.LoadURL(new LoadURLParams("http://www.google.com", 
            "{\"title\":\"Hello\"}", "Content-Type: application/json\n"));

To find out when web page is loaded completely use Load Events.