XMLHttpRequest Equivalent in C#

I have to create a simple winform which will take in the URL and the input request XML as a parameter and once the user hits the Submit button, the response has to be submitted in a text box. I implemented the same in a .html file and the sequence of operations after the Submit button is hit is shown below:

document.forms["testForm"].resultXML.value = 'Please Wait....'

              var xmlhttp = new XMLHttpRequest()

            xmlhttp.open("POST", document.forms["testForm"].uri.value,true);

            xmlhttp.setRequestHeader("Man", "POST " + document.forms["testForm"].uri.value + "HTTP/1.1")

            xmlhttp.setRequestHeader("MessageType", "CALL")

             xmlhttp.setRequestHeader("Content-Type", "text/xml")

             xmlhttp.send(document.forms["testForm"].requestXML.value)

             xmlhttp.onreadystatechange = function() {

                   document.forms["testForm"].resultXML.value = xmlhttp.responseText

                   }

            }

Sample code in C# will be helpful to do the above operations.