加入两个列表并使用linq选择嵌套项目

Question

I have a list of the following class:

public class SiloRelationship
{
    public int RelationshipType { get; set; }
    public string MasterKey { get; set; }
    public string SlaveKey { get; set; }
    public int QueryId { get; set; }
}

I have a second list of the following class:

public class SiloNode
{
    public string Key { get; private set; }
    public string Url { get; private set; }

    public List<NodeQuery> Queries { get; private set; }
}

Which has a sub-class:

public class NodeQuery
{
    public string Query { get; private set; }
    public int Seq { get; private set; }
}

Lists:

• LandingSilo.Relationships is a list of SiloRelationship
• LandingSilo.Nodes is a list of SiloNode.

Here's my query - there is a simple join, after which I need to return the Url and Query properties - the filter should result in a single QueryNode from the list.

What we have is:

SiloRelationship => 1 to 1 SiloNode => 1 to many QueryNode 

A Kvp would be adequate for the purpose of the exercise but I can't see the Query property with the code I've got so far.

var query =
    from r in LandingSilo.Relationships
    join n in LandingSilo.Nodes on r.SlaveKey equals n.Key
    where r.RelationshipType == 1 &&
    n.Queries.Select(y => y.Seq).Contains(r.QueryId)

Any help appreciated.

Answer 1

You just need to filter the Queries . Change last statement like below

select n.Queries.FirstOrDefault(q => q.Seq == q.QueryId);

Answer 2

Try this:

IEnumerable<string> queries = LandingSilo.Relationships
    .Where(r => r.RelationshipType == 1)
    .Join(
        LandingSilo.Nodes, 
        r => r.SlaveKey, 
        n => n.Key, 
        (r, n) => n.Queries.SingleOrDefault(q => q.Seq == r.QueryId))
    .Where(q => q != null)
    .Select(q => q.Query);

Line by line: filter all Relationship s with type different from 1 , join on SlaveKey / Key and select the only query in the node that has the Seq equal to the Relationship s QueryId . Filter out null results and select the Query property. This is going to throw an InvalidOperationException if there are multiple queries within one node matching.

This can be also done in the LINQ keyword syntax like this:

IEnumerable<string> queries = 
    from r in LandingSilo.Relationships
    where r.RelationshipType == 1
    join n in LandingSilo.Nodes on r.SlaveKey equals n.Key
    from q in n.Queries.SingleOrDefault(q => q.Seq == r.QueryId)
    where q != null
    select q.Query;