按关系排序属性使用 Neo4jClient C#

Question

我想在 C# 等效项中获取以下查询：

match(p:Person)-[r1:HAS]->(s:Shelf) 
optional match(s)-[r2:CONTAINS]->(l:Link) return p,s,l 
order by r2.time_modified;

我最初考虑过这个，但它不起作用：

var result = await this._graphClient.Cypher
                 .Match("(person:Person { person_id: {personId}})-[r1:HAS]->(shelf:Shelf)")
                 .OptionalMatch("(shelf)-[r2:CONTAINS]->(link:Link)")
                 .WithParams(new { personId = personId })
                 .Return((shelf, link) => new 
                  {
                     Shelf = shelf.As<Shelf>(),
                     Links = link.CollectAs<Link>()
                  })
                 .OrderBy("r2.time_modified")
                 .ResultsAsync;

我收到以下异常，表示 r2 未定义

r2 not defined ... "ORDER BY r2.time_modified"

我对使用 Neo4jClient C# 驱动程序比较陌生。任何人都可以帮助我并向我解释发生了什么事吗？我也想知道如何解决这个问题。

这是堆栈跟踪：

at System.Threading.Tasks.Task.ThrowIfExceptional(Boolean includeTaskCanceledExceptions) at System.Threading.Tasks.Task1.GetResultCore(Boolean waitCompletionNotification) at System.Threading.Tasks.Task1.get_Result() at Neo4jClient.GraphClient.<>c__851.<PrepareCypherRequest>b__85_1(Task1 response) in D:\temp\d298ce3\Neo4jClient\GraphClient.cs:line 961 at System.Threading.Tasks.ContinuationResultTaskFromResultTask2.InnerInvoke() at System.Threading.Tasks.Task.Execute() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.ConfiguredTaskAwaitable1.ConfiguredTaskAwaiter.GetResult() at Neo4jClient.GraphClient.d__871.MoveNext() in D:\temp\d298ce3\Neo4jClient\GraphClient.cs:line 1022 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at System.Runtime.CompilerServices.TaskAwaiter1.GetResult() at ....Repository.Neo4jRepository.d__23.MoveNext() in C:\Users\Williams\documents\visual studio 2015\Projects...\Repository\Neo4jRepository.cs:line 358

Answer 1

您需要 RETURN r2.time_modified 才能按它排序结果。

match(p:Person)-[r1:HAS]->(s:Shelf) 
optional match(s)-[r2:CONTAINS]->(l:Link) 
return p,s,l,r2.time_modified
order by r2.time_modified;

如果返回，您可以将其用于 ORDER BY。

[编辑]

未测试：

var result = await this._graphClient.Cypher
                 .Match("(person:Person { person_id: {personId}})-[r1:HAS]->(shelf:Shelf)")
                 .OptionalMatch("(shelf)-[r2:CONTAINS]->(link:Link)")
                 .WithParams(new { personId = personId })
                 .Return((shelf, link, r2) => new 
                  {
                     Shelf = shelf.As<Shelf>(),
                     Links = link.CollectAs<Link>()
                  })
                 .OrderBy("r2.time_modified")
                 .ResultsAsync;

Answer 2

因为您在 Return 语句中执行了 Collect，所以 r2 不再存在。

您需要先下单，然后返回：

var query = gc.Cypher
    .Match("(p:Person { person_id: 'a'})-[r1:HAS]->(s:Shelf)")
    .OptionalMatch("(s)-[r2:CONTAINS]->(l:Link)")
    .With("p,s,l")
    .OrderBy("r2.time_modified")
    .Return((p,s,l) => new
    {
         Person = p.As<Person>(),
         Shelf = s.As<Shelf>(),
         Links = l.CollectAs<Link>()
    });
var res = query.Results;

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