实体框架模型属性无法正确更新 [英] Entity Framework Model Property not update properly

问题描述

我有以下2种模型。

GeoLocation 模型：

public class GeoLocation {
        public GeoLocation() { }
        public int Id { get; set; }
        public double Latitude { get; set; }
        public double Longitude { get; set; }
    }

Provider Model：

public class Provider
    {
        public Provider()
        {
            Id = Guid.NewGuid();
            Created = DateTime.Now;
        }

        public Guid Id { get; set; }
        [Required]
        public string Name { get; set; }

        public virtual GeoLocation Location { get; set; }

    }

Repository / p>

Repository method :

public void SetLocation(string providerKey, GeoLocation location)
        {
            var provider = (from p in Catalog.Providers
                            where p.Key == providerKey
                            select p).Single();

            provider.Location = location;

            Catalog.SaveChanges();
}

像上面一样，我需要更新Provider Table的Location对象。是给出奇怪的结果。这是当传入位置对象有Id，我们说15.然后我需要更新到提供程序表位置Id .But之后的代码它更新因为16不是15.你能告诉我为什么吗？这里的根本问题是什么？

As like above I need to update Location object of Provider Table.But Above code is giving weird result.That is when incoming location object having Id let's say 15.Then I need to update that Id into provider tables location Id.But After above code It updates as 16 not as 15.Could you tell me Why ? What is the fundamental issue here ?

注意：我使用默认EF约定映射。

UPDATE：我发现这里的问题。当我把 provider.Location = location; GeoLocation 表自动增加ID增加1 。这是什么原因。我怎么能避免这种情况？

UPDATE: I have found the issue here.That is when I put provider.Location = location; GeoLocation table Auto increment Id increase by 1.That is the cause.So How could I avoid that ?

推荐答案

您是如何获得位置的？问题是你的EF上下文（ Catalog ）认为该位置是一个要持久化的新对象（=它生成插入到位置表中）。

How did you get the location? The problem is that your EF context (Catalog) believes that the location is a new object to be persisted (= it generates insert into the location table). You must inform catalog that it is already existing object.

这可能是一个诀窍：

if (location.Id > 0) {
    Catalog.GeoLocations.Attach(location);
} 

provider.Location = location;

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