使用通用存储库更新多对多关系

Question

我有一个禁用延迟加载的数据库上下文.我正在使用急切加载来加载我的所有实体.我无法更新多对多的关系.

这是存储库.

public class GenericRepository<TEntity> : IGenericRepository<TEntity>
        where TEntity : class
{
    ... other code here...

    public virtual void Update(TEntity t)
    {
        Set.Attach(t);
        Context.Entry(t).State = EntityState.Modified;
    }

    ...other code here...
}

这是用户模型.

public partial class User
{
    public User()
    {
        this.Locks = new HashSet<Lock>();
        this.BusinessModels = new HashSet<BusinessModel>();
    }

    public int UserId { get; set; }
    public string Username { get; set; }
    public string Name { get; set; }
    public string Phone { get; set; }
    public string JobTitle { get; set; }
    public string RecoveryEmail { get; set; }
    public Nullable<double> Zoom { get; set; }

    public virtual ICollection<Lock> Locks { get; set; }
    public virtual ICollection<BusinessModel> BusinessModels { get; set; }
}

如果我修改了业务模型集合,虽然我已经附加了整个实体,但它并没有保存业务模型集合.

Worker.UserRepository.Update(user);

我不确定发生了什么.我不想破坏我的通用存储库/工作单元模式只是为了更新多对多关系.

编辑2:我有这个工作......但它与我想要的模式有很大的不同.有了硬实现意味着我需要为每个具有多对多关系的类型创建一个方法.我现在正在调查,看看我是否可以将其作为通用方法.

编辑3:所以之前的实现我没有像我想的那样工作.但现在,我有一个稍微有效的实现.如果有人愿意帮助我,我可以继续这样做,我会永远爱你.

public virtual void Update(TEntity updated,
    IEnumerable<object> set,
    string navigationProperty,
    Expression<Func<TEntity, bool>> filter,
    Type propertyType)
{
    // Find the existing item
    var existing = Context.Set<TEntity>().Include(navigationProperty).FirstOrDefault(filter);

    // Iterate through every item in the many-to-many relationship
    foreach (var o in set)
    {
        // Attach it if its unattached
        if (Context.Entry(o).State == EntityState.Detached)
            // Exception "an object with the same key already exists"
            // This is due to the include statement up above. That statement
            // is necessary in order to edit the entity's navigation
            // property.
            Context.Set(propertyType).Attach(o);
    }

    // Set the new value on the navigation property.
    Context.Entry(existing).Collection(navigationProperty).CurrentValue = set;

    // Set new primitive property values.
    Context.Entry(existing).CurrentValues.SetValues(updated);
    Context.Entry(existing).State = EntityState.Modified;
}

然后我这样称呼它:

Worker.UserRepository.Update(user, user.BusinessModels, "BusinessModels", i => i.UserId == user.UserId, typeof (BusinessModel));

非常混乱,但它让我可以更新与泛型的多对多关系.当我去附加已经存在的新值时,我的大问题是异常.由于include语句,它们已经加载.

这有效:

这不是:

Answer 1

经过许多痛苦的工作,我终于找到了一种方法来更新与完全通用的存储库的多对多关系.这将允许我创建(并保存)许多不同类型的实体,而无需为每个实体创建样板代码.

此方法假定:

• 您的实体已存在
• 您的多对多关系存储在具有复合键的表中
• 您正在使用预先加载来将关系加载到上下文中
• 您正在使用工作单元/通用存储库模式来保存实体.

这是Update通用方法.

public virtual void Update(Expression<Func<TEntity, bool>> filter,
    IEnumerable<object> updatedSet, // Updated many-to-many relationships
    IEnumerable<object> availableSet, // Lookup collection
    string propertyName) // The name of the navigation property
{
    // Get the generic type of the set
    var type = updatedSet.GetType().GetGenericArguments()[0];

    // Get the previous entity from the database based on repository type
    var previous = Context
        .Set<TEntity>()
        .Include(propertyName)
        .FirstOrDefault(filter);

    /* Create a container that will hold the values of
        * the generic many-to-many relationships we are updating.
        */
    var values = CreateList(type);

   /* For each object in the updated set find the existing
        * entity in the database. This is to avoid Entity Framework
        * from creating new objects or throwing an
        * error because the object is already attached.
        */
    foreach (var entry in updatedSet
        .Select(obj => (int)obj
            .GetType()
            .GetProperty("Id")
            .GetValue(obj, null))
        .Select(value => Context.Set(type).Find(value)))
    {
        values.Add(entry);
    }

    /* Get the collection where the previous many to many relationships
        * are stored and assign the new ones.
        */
    Context.Entry(previous).Collection(propertyName).CurrentValue = values;
}

这是我在网上找到的一个帮助方法,它允许我根据我提供的任何类型创建通用列表.

public IList CreateList(Type type)
{
    var genericList = typeof(List<>).MakeGenericType(type);
    return (IList)Activator.CreateInstance(genericList);
}

从现在开始,这就是要求更新多对多关系的内容:

Worker.UserRepository.Update(u => u.UserId == user.UserId,
    user.BusinessModels, // Many-to-many relationship to update
    Worker.BusinessModelRepository.Get(), // Full set
    "BusinessModels"); // Property name

当然,最后你需要去某个地方打电话:

Context.SaveChanges();

我希望这可以帮助那些从未真正发现如何在Entity Framework中使用通用存储库和工作单元类的多对多关系的人.