I deployed my code to a test server. There are two applications, the first one is for calling the second application. The 2nd one is the application that will do all the works.

This is the error page:

Basically, the first application has button which will call a URL:

The call code:

ScriptManager.RegisterStartupScript(Page, Page.GetType, "NewWindow", "window.open('" + ConfigurationManager.AppSettings("TweetURL_EN") + "');", True)

The URL is like this in the web.config:

<add key="TweetURL_EN" value="https://domain/Home/Index?ID=RandomNUMBER&amp;lang=e"/>

The second application is for posting a tweet that will return the tweet page.

It's ASP.NET Core MVC written in C#. It has a HomeController to call the Index.cshtml as action result (I don't encounter error on this, I think).

This the launchSettings.json for the 2nd application: do I need to change the applicationURL to the test server domain? It's still in localhost when I deployed it to the test server.

The 1st application works, it calls the 2nd application but when you run it for the first time, the error page will show up but will still call the twitter page which still works. But the error page shouldn't be there.

Maybe you guys know what to do on this. Thanks in advance!

I tried to google for an answer. But there's no specific to my problem.