C# 命名空间中不存在类型或命名空间名称

type or namespace name does not exist in the namespace

提问by user1300580

I have the code below in a .cs file and I am coming across the errors below, any help would be appreciated.

我在 .cs 文件中有下面的代码，我遇到了下面的错误，任何帮助将不胜感激。

using System.Data.Entity;

namespace Assignment2.Models
{
    public class TicketBookingEntities : DbContext
    {
        public DbSet<Performance> Performances { get; set; }
        public DbSet<Production> Productions { get; set; }
    }
}

Errors:

错误：

Error   1   The type or namespace name 'Entity' does not exist in the namespace 'System.Data' (are you missing an assembly reference?)
Error   2   The type or namespace name 'DbContext' could not be found (are you missing a using directive or an assembly reference?)
Error   3   The type or namespace name 'DbSet' could not be found (are you missing a using directive or an assembly reference?)
Error   4   The type or namespace name 'DbSet' could not be found (are you missing a using directive or an assembly reference?)

采纳答案by Daniel Hilgarth

Make sure your project contains a reference to EntityFramework.dll.
See the topic To add a reference in Visual C#in this linkif you don't know how to add a reference.

确保您的项目包含对EntityFramework.dll的引用。如果您不知道如何添加引用，
请参阅此链接中的主题在 Visual C#中添加引用。

回答by Nikhil Agrawal

Try looking for your missing references in Object Browser.

尝试在对象浏览器中查找丢失的引用。