使用以下数据库架构:
CREATE TABLE master (
id integer primary key autoincrement,
title text);
CREATE TABLE slave (
id integer primary key autoincrement,
master_id integer not null,
title text,
foreign key (master_id) references master (id));
我创建了一个 sqlite 数据库,然后我用它来创建一个 Entity Framework .edmx 文件。
然后我添加了一个主记录和一个从记录,它工作正常,然后我尝试删除从记录,但是这引发了一个异常,我不知道为什么。
var ctx = new blaEntities();
var newMaster = master.Createmaster(0);
ctx.masters.AddObject(newMaster);
var newSlave = slave.Createslave(0, 0);
newMaster.slaves.Add(newSlave);
ctx.SaveChanges(); // works fine, both id and master_id properties of newMaster
// and newSlave are then set with generated values.
newMaster.slaves.Remove(newSlave);
ctx.SaveChanges(); // InvalidOperationException is raised
异常信息是:
The operation failed: The relationship could not be changed because one or more of the foreign-key properties is non-nullable. When a change is made to a relationship, the related foreign-key property is set to a null value. If the foreign-key does not support null values, a new relationship must be defined, the foreign-key property must be assigned another non-null value, or the unrelated object must be deleted.
我做错了什么?
编辑:
这是由 EF Createslave(...)
方法生成的:
public static slave Createslave(global::System.Int64 id, global::System.Int64 master_id)
{
slave slave = new slave();
slave.id = id;
slave.master_id = master_id;
return slave;
}
最佳答案
在你的slave表中还有一个slave对象在masterId列中没有设置值。
尝试使用 ctx.DeleteObject(newSlave)
来摆脱它。
关于c# - 为什么 EntityCollection.Remove() 会导致 SaveChanges() 引发 InvalidOperationException?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/11309423/