LINQ:基于分组在子列表属性 [英] LINQ: grouping based on property in sublist
问题描述
我'尝试使用LINQ来创建文档基于元数据的分组列表,它是在文档列表。
下面是如何我的对象结构如下:
名单,其中,文件>
- >名单<元数据>
- >元数据有一个名字和一个value属性。
我想组在此基础上有一个名字的元数据标签的文件:ID和他们群里的ID属性的值是相同的。
我想它是这样的:
变种X = response.Document
.GroupBy(D => d.Metadata.Where(DC => dc.Name == DocProperty.ID)
。选择(DC => dc.Value));
这导致在单个文档的列表,而不是分组的ID。
也想过通过文件列表中选择ID的一个独特的列表,然后循环,找到匹配的ID文件。那一个似乎是一个很大的开销,因为在不同的列表中的每个ID我有充分的时间去到元数据列表,找到的文件,并有额外的多个项目的检查发现,得到我需要等属性。
任何人有关于如何让这件事的工作是个好主意?
VAR X =从文档源
从元在doc.Metadata
其中,meta.Name == DocProperty.Id
DOC组由meta.Value;
或(评论)流利的符号:
变种Y =源
.SelectMany(DOC => doc.Metadata,(文件,元)=>新建{文档,元})
。凡(双=> pair.meta.Name == DocProperty.Id)
.GroupBy(双=> pair.meta.Value,对=> pair.doc);
I'am trying to use LINQ to create a grouped list of documents based on metadata which is a list on the document.
Below is how my object structure looks:
List<Document>
--> List<Metadata>
--> Metadata has a name and a value property.
I want to group the documents based on an metadata tag which has a name: ID and group them where the values for the ID property are the same.
I tried it like this:
var x = response.Document
.GroupBy(d => d.Metadata.Where(dc => dc.Name == DocProperty.ID)
.Select(dc => dc.Value));
This results in a list of single documents, but not grouped on ID.
Also thought about selecting a distinct list of ID's and then loop through the document list and find documents that match the ID. That one seems like a lot of overhead, because for every ID in the distinct list i have to go every time into the metadata list and find the documents and have to extra checks for multiple items found, get the property i need etc.
Anyone has a good idea about how to get this thing working?
var x = from doc in source
from meta in doc.Metadata
where meta.Name == DocProperty.Id
group doc by meta.Value;
Or (comments) as fluent notation:
var y = source
.SelectMany(doc => doc.Metadata, (doc, meta) => new { doc, meta })
.Where(pair => pair.meta.Name == DocProperty.Id)
.GroupBy(pair => pair.meta.Value, pair => pair.doc);
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