Cannot redirect another page in ASP.NET Core MVC project Controller - asp.net-core

Question

I would like to press a button to connect a GET api, do something and redirect the page.
const Http = new XMLHttpRequest();
Http.open("GET", '/Startup/Action/Test');
Http.send();
Http.onreadystatechange = (e) => {
console.log(Http.responseText)
}
Then in my Controller:
[HttpGet("Startup/Action/{Handle}")]
public IActionResult Action(string Handle)
{
this.ViewData["Result"] = Handle;
return this.Ok(Handle);
// return LocalRedirect("~/Startup/");
// return Redirect("http://localhost:50429/");
// return View("~/Views/Startup/Index.cshtml");
// return Redirect("/");
// return RedirectToAction("Index", "Startup");
}
I get response and see it in console written by the javascript XMLHttpRequest event. However I cannot redirect to just another page. I tried all options commented above as return value.

Answer 1

With AJAX you don't perform the redirect server-side, you perform it client-side after the result has been received. Something like this:
Http.onreadystatechange = (e) => {
if(xhr.readyState === 4 && xhr.status === 200) {
window.location.href = '#Url.Action("Index", "Startup")';
} else {
// non-success reaponse? do something else?
}
}
The above code would redirect following a successful AJAX response. Note that this JavaScript code would need to be on a view itself in order to use the Url.Action() helper. If the JavaScript code is in a separate file, one option could be to return as a string in the AJAX response the URL to which you are redirecting.
Note however that what you are doing is a bit different here:
this.ViewData["Result"] = Handle;
I could be wrong, but I suspect this won't carry over on a redirect. TempData might? But ultimately the question then becomes... What exactly are you trying to accomplish? You are sending a value to the server and then trying to redirect the user to another page to include that value. Well, the client already knows that value, and since it's AJAX the client needs to perform the redirect, so is this AJAX operation even necessary at all?
It's not entirely clear to me what the overall goal here is, and I suspect the overall setup could be simplified significantly. But it looks like AJAX is needed at all here. You can revert your server-side code to performing the redirect and, instead of using AJAX, just redirect the client to that server-side action entirely:
window.location.href = '/Startup/Action/Test';
or:
winfow.location.href = '#Url.Action("Action", "Startup", new { Handle = "Test" })';
And then redirect in your server-side action as you originally tried:
[HttpGet("Startup/Action/{Handle}")]
public IActionResult Action(string Handle)
{
this.ViewData["Result"] = Handle;
return RedirectToAction("Index", "Startup");
}
It's still possible, and again I'm not certain, that ViewData isn't correct here and you may want to use TempData on a redirect. Though, again, it's equally likely that whatever you're trying to accomplish can be done so more effectively in the first place. Such as skipping this Action action method entirely and just passing the Handle value directly to the Index action, whatever it does it with that value.