在存储库中使用Include（）方法

我在EF 5中有以下内容：

var a = context.Posts.Include(x => x.Pack).Select(x => x.Pack.Id).ToList(); 

这很有效。 然后我尝试在我的通用存储库中复制它：

 public IQueryable Include(Expression<Func> criteria) where T : class { return _context.Set().Include(criteria); } 

但在这种情况下，我无法执行以下操作：

 var b = repository.Include(x => x.Pack).Select(x => x.Pack.Id).ToList(); 

我收到错误：

无法将类型’Data.Entities.Pack’隐式转换为’bool’

我怎么解决这个问题？

我应该在Include（）方法中更改什么？

Answer 1

尝试：

更改

 Expression> criteria 

至

 Expression> criteria 

编辑：要包含多个实体，您需要添加“包含”扩展名：

 public static class IncludeExtension { public static IQueryable Include(this IDbSet dbSet, params Expression>[] includes) where TEntity : class { IQueryable query = null; foreach (var include in includes) { query = dbSet.Include(include); } return query == null ? dbSet : query; } } 

然后你可以像这样使用它：

 repository.Include(x => x.Pack, x => x.Pack.Roles, ...).Select(x => x.Pack.Id).ToList(); 

只需确保“repository”返回“DbSet”对象。

Answer 2

我使用了接受的答案，但不得不为EntityFramework Core修改一下。 根据我的经验，我必须保持链条运行或以前的查询引用被覆盖。

  public IQueryable Include(params Expression>[] includes) { IIncludableQueryable query = null; if(includes.Length > 0) { query = _dbSet.Include(includes[0]); } for (int queryIndex = 1; queryIndex < includes.Length; ++queryIndex) { query = query.Include(includes[queryIndex]); } return query == null ? _dbSet : (IQueryable)query; } 

Answer 3

这就是我们在EF 6中所做的结果

  public IEnumerable GetIncludes(params Expression>[] includes) { IQueryable query = table.Include(includes[0]); foreach (var include in includes.Skip(1)) { query = query.Include(include); } return query.ToList(); }