Check out example codes for "set the page that FormsAuthentication.RedirectFromLoginPage redirects to". It will help you in understanding the concepts better.

Code Example 1

// RedirectFromLoginPage cannot specify a path. Use the following
FormsAuthentication.SetAuthCookie(IDTextBox.Text, RememberCheckBox.Checked);
Response.Redirect("some url the user has choosen");

Learn ReactJs, React Native from akashmittal.com