Strictly speaking, the question makes no sense, because
your HTML does nothing, it does not submit anything to the server, because the "Submit" button is missing; it should be
<input>
element with the type="submit".
But if I could assume you have it all, your form would submit some data using the method "post". The HTTP request would contain all the form elements' data in key-value pairs, with keys equal to corresponding values of
name
attributes.
To do the same thing in ASP.NET code behind, you could use the class
System.Net.HttpWebRequest
:
https://msdn.microsoft.com/en-us/library/system.net.httpwebrequest%28v=vs.110%29.aspx.
—SA