Window.Open() is showing a blank page

Here you need to pass absolute URL not relative one;

So in your case window.open('http://www.sitename.com/' + 'Home/Index.csHtml');

I need to open the window in a locally hosted application.

Then you can use the localhost in place of domain like this or whatever is your hostname:post if any http://localhost/Home/Index.csHtml

You're getting a blank page and if you look at the console you should have an error HTTP 404, page not found.

This is because csHTML files are not HTML files, they are MVC views that are processed by the MVC engine.
So what you need to use is the route that points to that view.
From the path you shared, big chances are that it's the root route, meaning just /
For instance:

window.open('/');

Select allOpen in new window

This will fail if you're running your site in a virtual directory, so take tat in consideration.

Yes. I am getting a blank page when giving Index.cshtml but there is no 404 error.

Also if I give Index instead of Index.cshtml, new window opened showing Access denied. Did I done anything wrong?

Thanks Guys..It worked.  I have given permission to my view.

While giving Index policy to view,  it worked.