[英]Orderby and thenby using LINQ
I have below table for categories. 我在下表中列出了类别。
tbCategories tbCategories
CatgID CatgName
------ --------
1 Catg1
2 Catg2
3 Catg3
4 Catg4
Now I have items table which is categorized linking to above categories 现在我有项目表,它被分类链接到上述类别
tbItem tbItem
ItemID ItemName ItemCatg Priority
------ -------- -------- --------
1 Name 1 1 1
2 Name 2 1 2
3 Name 3 2 1
4 Name 4 3 3
5 Name 5 4 2
6 Name 6 3 1
Priority 优先
1 - High
2 - Medium
3 - Low
Now when I display the item data, I want the to first display items with category Catg1
, Catg2
and Catg4
based on their priority, then display items with Catg3
based on their priority. 现在,当我显示项目数据时,我希望首先根据其优先级显示类别
Catg1
, Catg2
和Catg4
的项目,然后根据其优先级显示Catg3
的项目。
I had tried below LINQ
expression, but I did not succeed with that. 我曾尝试在
LINQ
表达式下进行操作,但没有成功。 My knowledge on LINQ
or SQL
is not too strong but that's how much I could reach. 我对
LINQ
或SQL
知识不是很强,但是我可以达到的水平。
model.items = db.tbItem.OrderBy(p=>p.ItemCatg).ThenBy(p=>p.Priority).ToList();
Could someone please show me the right way to achieve this functionality? 有人可以告诉我实现此功能的正确方法吗?
UPDATE UPDATE
I would like to achieve below combination while displaying. 我想在显示时实现以下组合。
ItemID ItemName ItemCatg Priority
------ -------- -------- --------
1 Name 1 1 1
3 Name 3 2 1
2 Name 2 1 2
5 Name 5 4 2
6 Name 6 3 1
4 Name 4 3 3
The following is a trick I've used in the past. 以下是我过去使用的技巧。 You're basically relying on the result of the comparison ordering things first by the non-3 categories (ie, the false equates to 0, the true to 1) then by the priority, then by the category.
您基本上是依靠比较结果的,首先是按非3类别(即false等于0,true等于1),然后是优先级,然后是类别对事物进行排序。
tbItems.OrderBy(p=>p.ItemCatg == 3).ThenBy(p=>p.Priority).ThenBy(p=>p.ItemCatg).ToList();
Here's a .NET Fiddle example. 这是一个.NET Fiddle示例。
Here's the output from the example: 这是示例的输出:
ItemID: 1 ItemName: Name 1 ItemCatg: 1 Priority: 1
ItemID: 3 ItemName: Name 3 ItemCatg: 2 Priority: 1
ItemID: 2 ItemName: Name 2 ItemCatg: 1 Priority: 2
ItemID: 5 ItemName: Name 5 ItemCatg: 4 Priority: 2
ItemID: 6 ItemName: Name 6 ItemCatg: 3 Priority: 1
ItemID: 4 ItemName: Name 4 ItemCatg: 3 Priority: 3
Edit 2: 编辑2:
You can use multiple queries like this: 您可以使用多个查询,如下所示:
var query1 = model.items.Where(x => x.ItemCatg != 3).OrderBy(y => y.Priority);
var query2 = model.items.Where(x => x.ItemCatg == 3).OrderBy(y => y.Priority);
var query = query1.Concat(query2);
Edit: 编辑:
If you want to group your item based on certain criteria, you probably could do something like this with LINQ: 如果要基于某些条件对项目进行分组,则可以使用LINQ进行以下操作:
model.items = db.tbItem.GroupBy(p=>p.ItemCatg)
.OrderBy(p=>p.Priority).ToList();
This will give you groups based on ItemCatg
and among that group, you order it by Priority
. 这将为您提供基于
ItemCatg
组,在该组中,您可以按Priority
对其进行订购。
Original: 原版的:
Since your query is quite customized, you may consider to create a "mapping" between your actual column ItemCatg
value in tbItem
with the priority you want to assign: 由于查询是完全自定义的,因此您可以考虑在
tbItem
实际列ItemCatg
值与要分配的优先级之间创建一个“映射”:
ItemCatg -> Actual priority
1 -> 0
2 -> 1
4 -> 2 //here is the trick
3 -> 3
In that case, you could create list for mapping like this: 在这种情况下,您可以像这样创建映射列表:
List<int> prioMap = new List<int>() { 1, 2, 4, 3 };
And then use it like this: 然后像这样使用它:
model.items = db.tbItem.OrderBy(p=>prioMap.IndexOf(p.ItemCatg))
.ThenBy(p=>p.Priority).ToList();
Main trick: IndexOf
will give you the index
of the item ( ItemCatg
) in the list. 主要技巧:
IndexOf
将为您提供列表中项目( ItemCatg
)的index
。
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