这会做一个dense_rank()
. 根据您的需要更改GroupBy
和:) 基本上,是对查询的有序组进行编号,因此:Order
dense_rank
var DenseRanked = data.Where(item => item.Field2 == 1)
//Grouping the data by the wanted key
.GroupBy(item => new { item.Field1, item.Field3, item.Field4 })
.Where(@group => @group.Any())
// Now that I have the groups I decide how to arrange the order of the groups
.OrderBy(@group => @group.Key.Field1 ?? string.Empty)
.ThenBy(@group => @group.Key.Field3 ?? string.Empty)
.ThenBy(@group => @group.Key.Field4 ?? string.Empty)
// Because linq to entities does not support the following select overloads I'll cast it to an IEnumerable - notice that any data that i don't want was already filtered out before
.AsEnumerable()
// Using this overload of the select I have an index input parameter. Because my scope of work is the groups then it is the ranking of the group. The index starts from 0 so I do the ++ first.
.Select((@group , i) => new
{
Items = @group,
Rank = ++i
})
// I'm seeking the individual items and not the groups so I use select many to retrieve them. This overload gives me both the item and the groups - so I can get the Rank field created above
.SelectMany(v => v.Items, (s, i) => new
{
Item = i,
DenseRank = s.Rank
}).ToList();
另一种方法是 Manoj 在这个问题中的回答所指定的- 但我更喜欢它,因为从表中选择了两次。