实体框架6查询返回记录，其中数据尚未保存在数据库中 [英] Entity Framework 6 query returning record with data not yet saved in the database

问题描述

我使用Entity Framework 6 Code-first创建了一个非常简单的测试项目，我试图了解变更跟踪的工作原理.

I created a very simple test project using Entity Framework 6 Code-first and I'm trying to understand how change tracking works.

在我的简单测试中，我有一个Blogs表，我插入了一个名为"User1"的Blog，在插入并保存后，我修改了用于插入的对象(name ="User1 Modifyed")，但未保存更改.之后，我查询数据库.令我惊讶的是，即使更新后我没有保存更改，数据库查询仍返回修改后的记录.这是为什么?

In my simple test I have a Blogs table and I insert a Blog with a name "User1", after inserting and saving I modify the object used to insert (name="User1 modified") but without saving changes. Right after that I query my database. For my surprise the query from the db is returning the modified record even though I did not save my changes after the update. Why is that?

这是我的代码:

 class Program
{
    static void Main(string[] args)
    {
        using (var db = new BloggingContext())
        {
            // Create and save a new Blog 
            Console.Write("Enter a name for a new Blog: ");
            //var name = Console.ReadLine();

            var name = "User1";

            var blog = new Blog { Name = name };
            db.Blogs.Add(blog);
            db.SaveChanges();

            //Modify my blog name but don't save changes yet!
            blog.Name = "User1 modified";

            // Display all Blogs from the database 
            var query = from b in db.Blogs
                        orderby b.Name
                        select b;

            Console.WriteLine("All blogs in the database:");
            foreach (var item in query)
            {
                //item.Name comes as "User1 modified" instead of "User1" Why?????
                Console.WriteLine(item.Name);
            }

            Console.WriteLine("Press any key to exit...");
            Console.ReadKey();
        } 
    }
}
public class BloggingContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
}

public class Blog
{
    public int BlogId { get; set; }
    public string Name { get; set; }
} 

如何直接从数据库而不是从上下文中获取数据，即使没有保存更改，上下文也似乎保留了我的对象属性?

How can I get the data directly from the database instead of the Context, which seems to be holding my object properties even without saving changes?

谢谢！

原始项目教程可以在这里找到: http://msdn.microsoft.com/en-us/data/jj193542.aspx

The original project tutorial can be found here: http://msdn.microsoft.com/en-us/data/jj193542.aspx

推荐答案

我最终按照@LadislavMrnka的建议查询了实体 AsNoTracking :

I ended up querying my entities AsNoTracking as suggested by @LadislavMrnka:

var query = from x context.YourEntities.AsNoTracking() where ... select x;

如何强制EF Code First查询数据库?

这迫使EF每次都重新加载数据.在我的情况下它可以工作，因为我只需要从返回的对象中读取一些数据，而无需保存任何更改.

That forces EF to reload the data each time. It works in my case because I only need to read some data form my returning objects and I'm not saving any changes.

这篇关于实体框架6查询返回记录，其中数据尚未保存在数据库中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！