EF 包括其他实体（通用存储库模式）

Question

我在 Entity Framework Code First 之上使用通用存储库模式。一切正常，直到我需要在查询中包含更多实体。我必须成功包含一个实体，但现在我不知道如何包含多个实体。看看我到目前为止得到了什么：

public IQueryable<TEntity> GetQuery<TEntity>() where TEntity : class
{
    var entityName = GetEntityName<TEntity>();
    return _objectContext.CreateQuery<TEntity>(entityName);
}

public IList<TEntity> GetQueryWithInclude<TEntity>(string toInclude) where TEntity : class
{
    var entityName = GetEntityName<TEntity>();
    return _objectContext.CreateQuery<TEntity>(entityName).Include(toInclude).ToList();
}

private string GetEntityName<TEntity>() where TEntity : class
{
    return string.Format("{0}.{1}", _objectContext.DefaultContainerName, _pluralizer.Pluralize(typeof(TEntity).Name));
}

我试图做但没有奏效的是将字符串数组传递给函数，然后尝试在查询顶部“附加”包含。我想知道如果我调用 GetQueryWithInclude 并一次传递一个实体名称（实际上是一个导航属性）来聚合查询结果，但我担心这可能会在每次调用时重复查询结果......您认为实现此功能的最佳方法是什么？

提前致谢！

更新：

这是我想要实现的一个示例：

public IQueryable GetQueryWithIncludes(string[] otherEntities)
{
    var entityName = GetEntityName<TEntity>();
    //now loop over the otherEntities array 
    //and append Include extensions to the query
    //so inside the loop, something like: 
    _objectContext.GetQuery<TEntity>(entityName).Include(otherEntities[index]);
}

Answer 1

仅在 IQueryable 上使用 Include 扩展。它在 EF 4.1 程序集中可用。如果您不想在上层中引用该程序集，请在数据访问程序集中创建包装扩展方法。

这里有例子：

public static IQueryable<T> IncludeMultiple<T>(this IQueryable<T> query, params Expression<Func<T, object>>[] includes)
    where T : class
{
    if (includes != null)
    {
        query = includes.Aggregate(query, 
                  (current, include) => current.Include(include));
    }

    return query;
}

您将使用它，例如：

var query = context.Customers
                   .IncludeMultiple(
                       c => c.Address,
                       c => c.Orders.Select(o => o.OrderItems));

此查询将加载所有客户及其地址和订单，每个订单都将包含其订单商品。

Answer 2

//我在这里包括了最低限度。下面是它的使用方法。

     IQueryable<File> xg= UnitOfWork.Files.GetAllLazyLoad(d => d.FileId == 1, 
            r => r.FileCategory);
//where r.FileCategory is a navigational property.

//Interface


    namespace Msh.Intranet.Repository.GenericRepoPattern
    {
        public interface IRepository<T> where T:class
        {

            IQueryable<T> GetAllLazyLoad(Expression<Func<T, bool>> filter, params Expression<Func<T, object>>[] children);

        }
    }



        namespace Msh.Intranet.Repository.GenericRepoPattern
        {
            /// <summary>
            /// The EF-dependent, generic repository for data access
            /// </summary>
            /// <typeparam name="T">Type of entity for this Repository.</typeparam>
            public class EFRepository<T> : IRepository<T> where T : class
            {
                public EFRepository(DbContext dbContext)
                {
                    if (dbContext == null)
                        throw new ArgumentNullException("dbContext");
                    DbContext = dbContext;
                    DbSet = DbContext.Set<T>();

                }

                protected DbContext DbContext { get; set; }

                protected DbSet<T> DbSet { get; set; }


                public virtual IQueryable<T> GetAllLazyLoad(Expression<Func<T, bool>> filter, params Expression<Func<T, object>>[] children) 
                {


                        children.ToList().ForEach(x=>DbSet.Include(x).Load());
                        return DbSet;
                }

            }
        }

Answer 3

Say goodbye to the hardcoded ObjectQuery(T).Include calls

如果您使用的是 EF > 4，那么它是内置的，请检查 DbExtensions.Include on MSDN。

Answer 4

对于实体框架，创建一个字符串列表来保存包含。请参阅下面的示例代码

public virtual IQueryable<TObject> Filter(Expression<Func<TObject, bool>> filter,
                                              int skip = 0,
                                              int take = int.MaxValue,
                                              Func<IQueryable<TObject>, IOrderedQueryable<TObject>> orderBy = null,
                                              IList<string> incudes = null)
    {
        var _resetSet = filter != null ? DbSet.AsNoTracking().Where(filter).AsQueryable() : DbSet.AsNoTracking().AsQueryable();

        if (incudes != null)
        {
            foreach (var incude in incudes)
            {
                _resetSet = _resetSet.Include(incude);
            }
        }
        if (orderBy != null)
        {
            _resetSet = orderBy(_resetSet).AsQueryable();
        }
        _resetSet = skip == 0 ? _resetSet.Take(take) : _resetSet.Skip(skip).Take(take);

        return _resetSet.AsQueryable();
    }

更多详情请看以下链接 http://bulletproofcoder.com/blog/using-include-in-a-generic-entity-framework-repository

在entity framework core中我们将使用IIncludableQueryable。请参阅下面的示例代码

        public virtual IQueryable<TObject> Filter(Expression<Func<TObject, bool>> filter,
                                              int skip = 0,
                                              int take = int.MaxValue,
                                              Func<IQueryable<TObject>, IOrderedQueryable<TObject>> orderBy = null,
                                              Func<IQueryable<TObject>, IIncludableQueryable<TObject, object>> include = null)
    {
        var _resetSet = filter != null ? DbSet.AsNoTracking().Where(filter).AsQueryable() : DbSet.AsNoTracking().AsQueryable();

        if (include != null)
        {
            _resetSet = include(_resetSet);
        }
        if (orderBy != null)
        {
            _resetSet = orderBy(_resetSet).AsQueryable();
        }
        _resetSet = skip == 0 ? _resetSet.Take(take) : _resetSet.Skip(skip).Take(take);

        return _resetSet.AsQueryable();
    }