实体框架多对多通用更新

Question

我正在尝试使用EF6实现通用的多对多更新方法。 每次尝试更新导航属性时，都会出现一个异常：

“违反了PRIMARY KEY约束'PK_dbo.Classes'。无法在对象'dbo.Classes'中插入重复的键。重复的键值为（698d5483-eb48-4d7e-84e7-a9f95a243d3d）。\\ r \\ n该语句已终止。 “

我该如何解决？

public void Update(T entity, params Expression<Func<T, IEnumerable>>[] navProps)
{
    using (var context = new Context())
    {
        T foundEntity = context.Set<T>().Find(entity.Id);
        var entry = context.Entry(foundEntity);
        entry.CurrentValues.SetValues(entity);

        foreach (var prop in navProps)
        {
            string memberName;
            var member = prop.Body as MemberExpression;

            if (member != null)
            {
                memberName = member.Member.Name;
            }
            else
            {
                throw new Exception();
            }

            var collection = entry.Collection(memberName);
            collection.Load();
            collection.CurrentValue = typeof(T).GetProperty(memberName).GetValue(entity);
        }

        context.SaveChanges();
    }
}

Answer 1

最后，我找到了通用多对多更新的解决方案

 public void Update(Guid id, T record)
        {
            using (var context = new FortisDataStoreContext(_client, _user))
            {
                var set = context.Set<T>().AsQueryable();

                foreach (var x in GetNavigationProperties(context, record))
                {
                    foreach (var xx in x.PropertyType.GetGenericArguments())
                    {
                        set = set.Include(x.Name);
                    }
                }

                var entry = set.FirstOrDefault(x => x.Id == id && x.IsClosed == false);
                context.Entry(entry).CurrentValues.SetValues(record);

                foreach (var x in GetNavigationProperties(context, record))
                {
                    if(x.PropertyType.GetGenericArguments().Count() > 0)
                    {
                        var genericType = x.PropertyType.GenericTypeArguments[0];
                        var newValues = (IList)x.GetValue(record, null) ?? new object[0];
                        var genericList = CreateList(genericType);
                        foreach (var item in newValues)
                        {
                            var ident = item.GetType().GetProperty("Id").GetValue(item, null);
                            var obj = context.Set(genericType).Find(ident);
                            genericList.Add(obj);
                        }
                        context.Entry(entry).Collection(x.Name).CurrentValue = genericList;
                    }
                }

                context.SaveChanges();
            }
        }