Create connection between .NET website and Tableau server

Hello, We developed a .NET based web server where we are hosting Tableau dashboards, which will be carrying images of the dashboards on the front end and carrying a share link for dashboards on the backend. The web server will be accessible from outside the company's network. We have Cubes (SSAS) as our data source and we implemented Kerberos authentication onto it as we have Row-level security on the Cubes and we want to display only User respective data to the Users User from outside will access the website using his AD credentials and will be brought to the dashboards image page and when he clicks one the dashboard image it must display the dashboard on the same page itself in a pop-up window. We designed the server, gave access to it from outside, published dashboards onto it. Now when we access the website with our AD credentials and try to open the published dashboards it is showing two more sign-in windows 1. Domain sign in 2. Tableau server sign in. What we are trying to achieve is, 1. When the User logs in using his AD credentials, it must pass along that credentials to the Tableau server also and when he accesses the dashboard it must not ask for his login again. 2. Is there anyway so that when the Users use their AD login and login into the Web server, on the backend itself those credentials will be Tableau server also and he will get authenticated in parallel. It is of high priority right now. So any help ASAP will be greatly appreciated.