Question

I need to replace the host part of the Uri

HttpContext.Current.Request.Url.Host = "newDomain";

you can’t set host. Is there a quick and easy way to do this to a Uri for reusing it to redirect somewhere else?

Answer 1

Use the UriBuilder class to change URIs, e.g.

var original = HttpContext.Current.Request.Url;
var changed = (new UriBuilder(original) { Host = "newDomain" }).Uri;

URIs are tricky little beasts with plenty of semantics you might not know or expect, so don’t go using string functions on them unless you absolutely have to.