MVC 5 + EF 6

(a)?? Operator

Two question marks in C # ("?") ) is the function of judging "?" Whether the object on the left is null, or "?" if it is not null. The left object, if NULL, uses the "?" The object on the right.

(ii) vs installation Entity Framework

Tools--Library Package Manager--Package manager background

In the Package Manager console, enter the following command and execute

Install-package EntityFramework

Three VS Install PAGEDLIST.MVC NuGet package

In the Package Manager console, enter the following command and execute

MVC 5 + EF 6