我该如何分组这些对象?我可以通过LINQ并绑定它。但这没用,因为我需要反向分组。像那样 :
MainGroup>组列表>子组列表
也许我可以使用LINQ查询首先获取值。我不知道。
我是LINQ的入门用户。我没有太多信息。预先感谢您的帮助。我得到并绑定mongodb数据:
var subGroupCollection = Database.GetCollection<SubGroup>(typeof(SubGroup).Name);
var groupCollection = Database.GetCollection<Group>(typeof(Group).Name);
var mainGroupCollection = Database.GetCollection<MainGroup>(typeof(MainGroup).Name);
var query = from sg in subGroupCollection.AsQueryable()
join mg in mainGroupCollection on sg.MainGroupId equals mg.Id into mainGroups
join z in groupCollection on sg.GroupId equals z.Id into groups
select new SoccerOddType
{
Id = sg.Id,
IsActive = sg.IsActive,
GroupId = sg.GroupId,
Name = sg.Name,
LastUpdateDate = sg.LastUpdateDate,
CreatedDate = sg.CreatedDate,
Order = sg.Order,
Discount = sg.Discount,
DiscountType = sg.DiscountType,
MainGroupId = sg.MainGroupId,
MainGroup = mainGroups.First(),
Group = groups.First()
};
来自:
public class MainGroup
{
public string Id { get; set; }
public string Name { get; set; }
public bool IsActive { get; set; }
}
public class Group
{
public string Id { get; set; }
public string MainGroupId { get; set; }
[BsonIgnore] public Group MainGroup { get; set; }
public string Name { get; set; }
public bool IsActive { get; set; }
}
public class SubGroup
{
public string Id { get; set; }
public string Name { get; set; }
public string MainGroupId { get; set; }
public string GroupId { get; set; }
[BsonIgnore] public Group MainGroup { get; set; }
[BsonIgnore] public Group Group { get; set; }
public bool IsActive { get; set; }
public decimal Discount { get; set; }
public EnmDiscountType DiscountType { get; set; }
}
至 :
public class MainGroupViewModel
{
public string Id { get; set; }
public string Name { get; set; }
public bool IsActive { get; set; }
public List<GroupViewModel> Groups { get; set; }
}
public class GroupViewModel
{
public string Id { get; set; }
public string MainGroupId { get; set; }
public string Name { get; set; }
public bool IsActive { get; set; }
public List<SubGroupViewModel> SubGroups { get; set; }
}
public class SubGroupViewModel
{
public string Id { get; set; }
public string Name { get; set; }
public string MainGroupId { get; set; }
public string GroupId { get; set; }
public bool IsActive { get; set; }
public decimal Discount { get; set; }
public EnmDiscountType DiscountType { get; set; }
}
如果你有一对多的关系,使用外键,并且你想要他们的子项目,例如学校与他们的学生,客户与他们的订单,MainGroups与他们的子组,那么你可以使用一个简单的选择得到你的结果,或使用GroupJoin
var result = mainGroupCollection.Select(mainGroup => new MainGroupViewModel
{
Id = mainGroup.Id,
Name = mainGroup.Name,
...
// Keep only the Groups of this MainGroup, using foreign key
Groups = groupCollection
.Where(group => group.MainGroupId == mainGroup.Id)
.Select(group => new GroupViewModel
{
Id = group.Id,
Name = group.Name,
...
// Keep only the subGroups of this Group, using foreign key
SubGroups = subGroupCollection
.Where(subGroup => subGroup.GroupId == group.Id)
.Select(subGroup => new SubGroupViewModel
{
Id = group.Id,
Name = group.Name,
...
})
.ToList(),
})
.ToList(),
});
尽管此方法有效,但效率不高,因为对于mainGroupCollection中的每个元素,它必须枚举整个GroupCollection,并且必须枚举整个SubGroupCollection的每个元素。
根据您从数据库查询时使用的DBMS,这不是一个大问题。但是,我会选择GroupJoin
Enumerable.GroupJoin更有效率(或相当于IQueryable)。 Enumerable版本使用Dictionary来查看它是否已找到具有此Id的项目,因此不需要在每个集合上多次枚举。
// GroupJoin the mainGroupCollection with the groupCollection:
var result = mainGroupCollection.GroupJoin(groupCollection,
mainGroup = mainGroup.Id, // from every mainGroup take the primary key
group => group.MainGroupId, // from every group take the foreign key
// ResultSelector: for every mainGroup and its groups make one MainGroupViewModel
(mainGroup, groupsOfThisMainGroup) => new MainGroupViewModel
{
Id = mainGroup.Id,
Name = mainGroup.Name,
...
// for the Groups: GroupJoin the groups of this main group with the subGroups
Groups = groupsOfThisMainGroup.GroupJoin(subGroupCollection,
groupOfThisMainGroup => groupOfThisMainGroup.Id,
subGroup => subGroup.GroupId,
// result selector
(group, subGroupsOfThisGroup) => new GroupViewModel
{
Id = group.Id,
Name = group.Name,
SubGroups = subGroupsOfThisGroup.Select(subGroup => new SubGroupViewModel
{
Id = subGroup.Id,
Name = subGroup.Name,
...
})
.ToList(),
})
.ToList(),
});
我可能会选择.Select()
。
var subGroups = subGroupCollection.Select(sg => new SubGroupViewModel
{
Id = sg.Id,
Name = sg.Name,
MainGroupId = sg.MainGroupId,
GroupId = sg.GroupId,
IsActive = sg.IsActive,
Discount = sg.Discount,
DiscountType = sg.DiscountType
});
var groups = groupCollection.Select(g => new GroupViewModel
{
Id = g.Id,
MainGroupId = g.MainGroupId,
Name = g.Name,
IsActive = g.IsActive,
SubGroups = subGroups.Where(sg => sg.GroupId == g.Id).ToList()
});
var mainGroups = mainGroupCollection.Select(mg => new MainGroupViewModel
{
Id = mg.Id,
Name = mg.Name,
IsActive = mg.IsActive,
// .Any() or .All() here?
Groups = groups.Where(g => g.SubGroups.Any(sg => sg.MainGroupId == mg.Id))
});