EF 5 AddOrUpdate复制数据 [英] EF 5 AddOrUpdate Duplicates data

问题描述

这是Seed方法中的代码：

This is the code in the Seed method:

var city = new City { Name = "A" };

var nh = new List<Neigh>
{
    new Neigh { City = city, Name = "N1" },
    new Neigh { City = city, Name = "N2" },
    new Neigh { City = city, Name = "N3" },
    //new Neigh { City = city, Name = "N4" },
};

context.Neighs.AddOrUpdate(
    p => p.Name,
    nh.ToArray()
);

在运行更新数据库后，一切正常。我可以多次运行它，而不会出现问题。但是，如果在某个时候取消注释第四个邻域并再次运行update-database，我最终会得到两个记录，其中城市为 A，N4指向该城市，其余的则指向原始城市。

After running update-database everything works as expected. I can run it multiple times without problem. However if at some point I uncomment the fourth neighborhood and run update-database again I end up with two records with city "A" and N4 is pointing to that city, while the rest point to the original city.

如果列表已更新，如何防止插入重复的城市？

How do I prevent the inserting of a duplicate city if the list gets updated?

推荐答案

您必须通过检查城市是否已经存在来启动脚本：

You must start the script by checking whether the city already exists:

var city = context.Cities.FirstOrDefault(c => c.Name == "A") 
                                     ?? new City { Name = "A" };

这篇关于EF 5 AddOrUpdate复制数据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！