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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