CODEWITHSUNDEEP
json.net
edencorbin
edencorbin

Reputation: 2929

Json.NET get nested jToken value

I am working at parsing a json http response with Json.NET and have working code, but am pretty sure I am going about it in an overly complicated way. My question is if there is a more direct way to get a child jToken by path and/or de-serialize it without foreaching every level.

I tried this approach but it returns null:

  JObject jObj = JObject.Parse( text );
  JToken myVal;
  jObj.TryGetValue( "response.docs", out myVal );

Here is my working overly complicated code, including de-serialization:

  JObject jObj = JObject.Parse( text );

  foreach( var kv in jObj ) {
    if( kv.Key == "response" ) {
      foreach( JToken jt in kv.Value ) {
        if( jt.Path == "response.docs" ) {
          JEnumerable<JToken> children = jt.Children();
          foreach( JToken t in children ) {       
            //THIS WORKS BUT IS NOT ELEGANT 
            Solr_User[] su = t.ToObject<Solr_User[]>();
          }
        }
      }
    }
  }

And here is the JSON raw response just for reference:

{
  "responseHeader":{
    "status":0,
    "QTime":0,
    "params":{
      "q":"*:*",
      "indent":"on",
      "wt":"json"}},
  "response":{"numFound":4,"start":0,"docs":[
      {
        "id":3,
        "first_name":"Bob",
        "_version_":"1558902640594649088"},
      {
        "id":4,
        "first_name":"Sam",
        "_version_":"1558902640613523456"},
      {
        "id":2,
        "first_name":"Fred",
        "_version_":"1558902640613523457"},
      {
        "id":1,
        "first_name":"Max",
        "_version_":"1558902640613523458"}]
  }}

Upvotes: 10

Views: 15371

Answers (1)

dbc
dbc

Reputation: 116585

You can use SelectToken() to select a token from deep within the LINQ-to-JSON hierarchy for deserialization. In two lines:

var token = jObj.SelectToken("response.docs");
var su = token == null ? null : token.ToObject<Solr_User []>();

Or in one line, by conditionally deserializing a null JToken when the selected token is missing:

var su = (jObj.SelectToken("response.docs") ?? JValue.CreateNull()).ToObject<Solr_User []>();

Sample fiddle.

In c# 6 or later it's even easier to deserialize a nested token in one line using the null conditional operator:

var su = jObj.SelectToken("response.docs")?.ToObject<Solr_User []>();

Or even

var su = jObj?["response"]?["docs"]?.ToObject<Solr_User []>();

Note that SelectTokens() is slightly more forgiving than the JToken index operator, as SelectTokens() will return null for a query of the wrong type (e.g. if the value of "response" were a string literal not a nested object) while the index operator will throw an exception.

Upvotes: 16

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