存储库模式获取一个实体并包含属性

Question

我通过这个通用方法在 C# 中使用存储库模式和实体框架：

public virtual IEnumerable<TEntity> Get(
        Expression<Func<TEntity, bool>> filter = null,
        Func<IQueryable<TEntity>, IOrderedQueryable<TEntity>> orderBy = null,
        string includeProperties = "")
    {
        IQueryable<TEntity> query = dbSet;

        if (filter != null)
        {
            query = query.Where(filter);
        }

        foreach (var includeProperty in includeProperties.Split
            (new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
        {
            query = query.Include(includeProperty);
        }

        if (orderBy != null)
        {
            return orderBy(query).ToList();
        }
        else
        {
            return query.ToList();
        }
    }

    public virtual TEntity GetByID(object id)
    {
        return dbSet.Find(id);
    }

现在我想为 GetByID 编写一个重载来接受包含属性，就像我使用的 Get 方法一样。像这样的：

    public virtual TEntity GetByID(object id, string includeProperties = "")
    {
        IQueryable<TEntity> query = dbSet;
        foreach (var includeProperty in includeProperties.Split
            (new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
        {
            query = query.Include(includeProperty);
        }            
        return ???
    }

我应该返回什么？有什么建议吗？

Answer 1

这完全取决于您的对象——您的实体是否实现了一个声明 ID 属性的通用接口？在这种情况下，您可以query.SingleOrDefault(e => e.Id == id)，但是，在似乎更有可能的情况下，您需要传入一个谓词来匹配或重新实现 Find() 功能。

在DBContext Find with Includes - where lambda with Primary keys 中，RBrowning99 从上下文中提取实体键并根据第一个键进行匹配：

public DALEntity Get(string ID, IEnumerable<string> IncludeEntities = null)
{
    var set = ((IObjectContextAdapter)context).ObjectContext.CreateObjectSet<DALEntity>();
    var entitySet = set.EntitySet;
    string[] keyNames = entitySet.ElementType.KeyMembers.Select(k => k.Name).ToArray();

    IQueryable<DALEntity> query = dbSet;
    query = IncludeEntities.Aggregate(query, (current, includePath) => current.Include(includePath));

    query = query.Where(keyNames[0] + "= @0", ID);
    return query.FirstOrDefault();
}