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PONeo4j .NET Client - Getting a Path from a Node to its Root
 

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  1. PONeo4j .NET Client - Getting a Path from a Node to its Root
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    <p>I'm experimenting with Neo4j for the first time. I've played a bit with the console (Cypher queries) and now I'm trying to use the .NET client to build a DAL for a .NET application.</p> <p>For now, my data model is very simple:</p> <ul> <li>I have nodes with a label "Folder".</li> <li>These nodes may have a "HAS_SUB_FOLDER" relationship with other folder nodes.</li> </ul> <p>I've successfully done some queries such as</p> <pre><code>MATCH (n:Folder) OPTIONAL MATCH n&lt;-[r:HAS_SUB_FOLDER]-parent WITH n, count(parent) AS parents WHERE parents = 0 RETURN n; </code></pre> <p>to get the parent-less nodes (i.e. "folders in the root directory") which translates to:</p> <pre><code>var myQuery = client.Cypher.Match("(folder:Folder)") .OptionalMatch("folder&lt;-[r:HAS_SUB_FOLDER]-parent") .With("folder, count(parent) AS parents") .Where("parents=0") .Return&lt;Folder&gt;("folder"); var res = myQuery.Results.ToList(); // res is a List&lt;Folder&gt;, Folder is a Model in my MVC architecture containing attributes like an ID and a Name. </code></pre> <p>in .NET.</p> <p>Now I'm trying to, <strong>for a given folder node, find the path to its root</strong> (to create some navigational breadcrumbs). The query I wrote for that is:</p> <pre><code>MATCH (current:Folder {id: "...THE_ID..."}) MATCH p = ((current)&lt;-[:HAS_SUB_FOLDER*1..5000]-()) RETURN p; </code></pre> <p>which seems to work.</p> <p>I can't, however, achieve that using the .NET client. I want to get a List with the ancestor folders for a given node. I have tried:</p> <pre><code>var getPathToRoot = client.Cypher.Match("(current:Folder)") .Where((Folder current) =&gt; current.ID == id) .Match("p = ((current) &lt;- [:HAS_SUB_FOLDER*1.." + MAX_DEPTH + "]-())") .Return&lt;Folder&gt;("NODES(p)"); var result = myQuery.Results.ToList(); </code></pre> <p>But I get a: <code>Accessed JArray values with invalid key value: "self". Array position index expected.</code> with the following raw JSON:</p> <pre><code>{ "columns" : [ "NODES(p)" ], "data" : [ [ [ { "labels" : "http://localhost:7474/db/data/node/21721/labels", "outgoing_relationships" : "http://localhost:7474/db/data/node/21721/relationships/out", "data" : { "Name" : "YYYYYYYY", "ID" : "e5daef28-84c0-42a8-85bf-32516bfe47d0" }, "traverse" : "http://localhost:7474/db/data/node/21721/traverse/{returnType}", "all_typed_relationships" : "http://localhost:7474/db/data/node/21721/relationships/all/{-list|&amp;|types}", "property" : "http://localhost:7474/db/data/node/21721/properties/{key}", "self" : "http://localhost:7474/db/data/node/21721", "outgoing_typed_relationships" : "http://localhost:7474/db/data/node/21721/relationships/out/{-list|&amp;|types}", "properties" : "http://localhost:7474/db/data/node/21721/properties", "incoming_relationships" : "http://localhost:7474/db/data/node/21721/relationships/in", "extensions" : { }, "create_relationship" : "http://localhost:7474/db/data/node/21721/relationships", "paged_traverse" : "http://localhost:7474/db/data/node/21721/paged/traverse/{returnType}{?pageSize,leaseTime}", "all_relationships" : "http://localhost:7474/db/data/node/21721/relationships/all", "incoming_typed_relationships" : "http://localhost:7474/db/data/node/21721/relationships/in/{-list|&amp;|types}"}, { "labels" : "http://localhost:7474/db/data/node/21720/labels", "outgoing_relationships" : "http://localhost:7474/db/data/node/21720/relationships/out", "data" : { "Name" : "XXXXXXXX", "ID" : "31a4cde4-8584-418f-a122-a0f84bbfbf92" }, "traverse" : "http://localhost:7474/db/data/node/21720/traverse/{returnType}", "all_typed_relationships" : "http://localhost:7474/db/data/node/21720/relationships/all/{-list|&amp;|types}", "property" : "http://localhost:7474/db/data/node/21720/properties/{key}", "self" : "http://localhost:7474/db/data/node/21720", "outgoing_typed_relationships" : "http://localhost:7474/db/data/node/21720/relationships/out/{-list|&amp;|types}", "properties" : "http://localhost:7474/db/data/node/21720/properties", "incoming_relationships" : "http://localhost:7474/db/data/node/21720/relationships/in", "extensions" : { }, "create_relationship" : "http://localhost:7474/db/data/node/21720/relationships", "paged_traverse" : "http://localhost:7474/db/data/node/21720/paged/traverse/{returnType}{?pageSize,leaseTime}", "all_relationships" : "http://localhost:7474/db/data/node/21720/relationships/all", "incoming_typed_relationships" : "http://localhost:7474/db/data/node/21720/relationships/in/{-list|&amp;|types}" } ] ] ] } </code></pre> <p>I can see that the data I want is being retrieved but there seems to be a problem when deserializing it. I've tried some variations on my code, with no success and I believe I have a newbie mistake somewhere while trying to get the nodes from the retrieved path.</p> <p>I'd appreciate if someone could help me with this as I'm just starting using Neo4j (and I'm still "hardwired" to <em>think RDBMS</em>), the documentation is (still) a bit sparse and I'm having issues with debugging (whenever I try to peek into the values of any variable from the Neo4j client library, I get a "Function evaluation disabled because a previous function evaluation timed out. You must continue execution to reenable function evaluation."). </p>
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