[英]How to check if a relation exists between two nodes using .net client of neo4j
I have a role based application and 2 nodes Role
and Cartable
and i am managing my permissions by creating a relation between these 2 nodes, if a relationship exists between these two nodes means this role has a permission for example to view the Cartable: 我有一个基于角色的应用程序和2个节点
Role
和Cartable
,我通过在这2个节点之间创建关系来管理权限,如果这两个节点之间存在关系,则意味着此角色具有例如查看Cartable的权限:
client.Cypher
.Merge("(s:SiteConfiguration)-[:"
+ Relations.ROLE_IN_SITE.ToString()+ "]-(r:Role)-[r1:"
+ Relations.ROLE_HAS_CARTABLE.ToString() + "]->(ca:Cartable)")
.Where("r.Id = {param}").WithParam("param", roleId)
.AndWhere("ca.Id= {param1}").WithParam("param1", cartableId)
.AndWhere("s.SiteId= {param2}").WithParam("param2", MvcApplication.SiteConfigurations.Base.SiteId)
.CreateUnique("(r)-[:" + Relations.EDIT_COMMENT.ToString()+"]-(ca)")
.ExecuteWithoutResults();
Now i want to check if relation exists between two nodes and return a Boolean based on that so i wrote this: 现在,我想检查两个节点之间是否存在关系,并基于该关系返回一个布尔值,所以我这样写:
var q = new CypherFluentQuery(client) as ICypherFluentQuery;
q = q.Match("(s:SiteConfiguration)-[:"
+ Relations.ROLE_IN_SITE.ToString() + "]-(r:Role)-[r1:"
+ Relations.VIEW_CARTABLE.ToString() + "]-(c:Cartable)");
q = q.Where("s.SiteId= {param}").WithParam("param", MvcApplication.SiteConfigurations.Base.SiteId);
q = q.AndWhere("r.Id= {param1}").WithParam("param1", roleId);
q = q.AndWhere("c.Id= {param2}").WithParam("param2", cartableId);
But I'm not sure what i should return here, since VIEW_CARTABLE
doesn't have any values as anonymous object on the relationship. 但是我不确定我应该在这里返回什么,因为
VIEW_CARTABLE
没有任何值作为关系上的匿名对象。 so my question is how to check if a certain relationship exists between these two nodes? 所以我的问题是如何检查这两个节点之间是否存在某种关系?
Because you are using a MATCH
- you won't get any results if r1
is not there. 因为您使用的是
MATCH
如果r1
不存在,则不会得到任何结果。 If you know you're going to get (s)-->(r)
- but not sure about (r)-->(c)
then you need to go OPTIONAL
. 如果您知道要获得
(s)-->(r)
-但不确定(r)-->(c)
则需要选择OPTIONAL
。
For example (using the :play Movies
db): 例如(使用
:play Movies
数据库):
var query = gc.Cypher
.Match("(p:Person {name:'Julia Roberts'})")
.OptionalMatch("(p)-[r]->(m:Movie)")
.Where("m.title = 'The Green Mile'")
.Return((p, m) => new
{
Person = p.As<Person>(),
Movie = m.As<Movie>(),
IsInMovie = Return.As<bool>("NOT (r IS NULL)")
});
Here I look for a person (Julia Roberts) and then try to see if she has a relationship to a given movie - in this case to one I know she's not in. 在这里,我寻找一个人(茱莉亚·罗伯茨),然后尝试看她是否与某部电影有关联-在这种情况下,与我知道她不在的一部电影有关。
I use an OptionalMatch
to do this, and then check if r
is null. 我使用
OptionalMatch
做到这一点,然后检查r
是否为null。
Now, in practice - I don't need to know about r
, as if there is no link to the movie, m
will be null
. 现在,在实践中-我不需要了解
r
,就好像没有电影的链接一样, m
将为null
。
In your case, you'd switch the top to be: 就您而言,您可以将顶部切换为:
var q = new CypherFluentQuery(client)
.Match("(s:SiteConfiguration)-[:ROLE_IN_SITE]-(r:Role)")
.OptionalMatch("(r)-[r1:VIEW_CARTABLE]-(c:Cartable)")
.Where("s.SiteId= {param}").WithParam("param", MvcApplication.SiteConfigurations.Base.SiteId)
.AndWhere("r.Id= {param1}").WithParam("param1", roleId)
.AndWhere("c.Id= {param2}").WithParam("param2", cartableId)
.Return((s,r,c,r1) => new {
Site = s.As<SiteConfiguration>(),
Role = r.As<Role>(),
Cartable = c.As<Cartable>(),
IsCartable = Return.As<bool>("NOT (r1 IS NULL)")
});
And you can either check if IsCartable
is true
or if Cartable == null
您可以检查
IsCartable
是否为true
或Cartable == null
我认为应该足以确定r1
是否不为null,因为获得非null值的唯一方法是关系是否存在。
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