ASP.NET MVC CORS issue - asp.net

Question

I have an ASP.NET MVC application (.NET 4.6) where on one occasion I need to redirect to a different domain.
So the code is like this (only authenticated users can come to the controller):
public ActionResult UploadForDesign(int parcelId)
{
......
string url = "differentdomain/parcelId" ;
return ReDirect(url);
}
I am getting an error:
has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin'.....
Failed to load resource: net::ERR_FAILED
I did the following in the control before redirect call
HttpContext.Response.AddHeader("Access-Control-Allow-Origin", "*");
and I still get the same error.
Also I tried the following in web.config, but didn't help much.
<httpProtocol>
<customHeaders>
<clear />
<add name="Access-Control-Allow-Origin" value="*" />
</customHeaders>
</httpProtocol>
Now I had another test bare ASP.NET MVC app (.NET 4.5.2) with no authentication, and the above code works fine. I checked all the code and it looks the same except authentication in place and the framework version.
Any idea what to do?

Answer 1

You can try to use the WithOrigins method on your CORS policy and add whatever domain you need:
services.AddCors(options =>
{
options.AddPolicy("CorsPolicy",
builder =>
.WithOrigins("http://localhost:4200/")
.AllowAnyMethod()
.AllowAnyHeader()
.AllowCredentials()
);
});
Ahhh sorry. I believe you should be able to use something like:
var p = new CorsPolicy();
p.AllowAnyHeader = true;
p.AllowAnyMethod = true;
p.AllowAnyOrigin = false;
p.Origins.Add("http://localhost:4200/");