Question

I have the following class written by someone else that I’m trying to understand (I omitted the code that is not necessary for this example):

public abstract class UserControl : System.Web.UI.UserControl
{
       ...

        public virtual bool IsAadmin(TheUser theUser)
        {
            if (Page is Page)
                return ((Page)Page).IsAadmin(theUser);

            return false;
        }
...

Edit: (note: in stackoverflow the first Page in the if statement is highlighted blue but in visual studio it isn’t)

In the if statement intellisense shows that the first Page is of type System.Web.UI.Page Control.Page and the second Page is from Something.Products.Web.Page. When I debug through the code, it doesn’t seem to go into this if statement, so I’m wondering what this code is trying to do? But more importantly where is that first Page in the if statement is coming from (initialized)? I’m using Resharper and it suggest replacing the if statement with

var page = Page as Page;
if (page != null)

This change shows that page is null when debugging through it.

Answer 1

The “first page” is actually a Page property of UserControl class your abstract UserControl inherits from. It’s of type System.Web.UI.Page and, as per documentation, returns

a reference to the Page instance that contains the server control.

The is keyword evaluates to true when

the provided expression is non-null, and the provided object can be cast to the provided type without causing an exception to be thrown.

It seems that when you were debugging your code, the examined UserControl was not contained in a page of type Something.Products.Web.Page.

Regarding the Resharper suggestion: in your original code, you are effectively casting the Page property twice – first, when using is keyword and second when casting it explicitly. With the code generated by Resharper, the cast only occurs once. When the if statement evaluates to true, you can be sure that the page variable holds a reference to the Something.Products.Web.Page and do not have to cast it again.