CODEWITHSUNDEEP
c#jsonjson.netjsonpath
jagadish
jagadish

Reputation: 41

JToken.SelectToken throws Newtonsoft.Json.JsonException Unknown escape chracter: \

Can someone help me with the correct JsonPath syntax to select the 'location' with the name 'US \ East'?

JObject location = new JObject();
location.Add("name", @"US \ East");

JArray locations = new JArray();
locations.Add(location);

JObject properties = new JObject();
properties.Add("locations", locations);

string path = "locations[?(@.name == 'US \\ East')]";
JToken item = properties.SelectToken(path);

The last line throw the following exception:

Newtonsoft.Json.JsonException was unhandled
_HResult=-2146233088
_message=Unknown escape chracter: \ 
HResult=-2146233088
IsTransient=false
Message=Unknown escape chracter: \ 
Source=Newtonsoft.Json
StackTrace:
  at Newtonsoft.Json.Linq.JsonPath.JPath.ReadQuotedString()
  at Newtonsoft.Json.Linq.JsonPath.JPath.ParseValue()
  at Newtonsoft.Json.Linq.JsonPath.JPath.ParseExpression()
  at Newtonsoft.Json.Linq.JsonPath.JPath.ParseQuery(Char indexerCloseChar)
  at Newtonsoft.Json.Linq.JsonPath.JPath.ParseIndexer(Char indexerOpenChar)
  at Newtonsoft.Json.Linq.JsonPath.JPath.ParsePath(List`1 filters, Int32 currentPartStartIndex, Boolean query)
  at Newtonsoft.Json.Linq.JsonPath.JPath.ParseMain()
  at Newtonsoft.Json.Linq.JsonPath.JPath..ctor(String expression)
  at Newtonsoft.Json.Linq.JToken.SelectToken(String path, Boolean errorWhenNoMatch)
  at Newtonsoft.Json.Linq.JToken.SelectToken(String path)
  at JsonPath.Program.Main(String[] args)

Upvotes: 4

Views: 974

Answers (1)

Serge
Serge

Reputation: 43880

It seems that json path is very tricky. Nobody could find any solution for more then 4 years already.

You have to use " @ " for the path string. This way json will get " \ \ " (double backslashes) and translate one as escape character. Without "@" json get only one " \ ", translates it as " \E " and throws an exception

string path = @"locations[?( @.name == 'US \\ East')]";
var item = properties.SelectToken(path);

I can also offer you another way using Linq

var item=  properties["locations"]
.Select(a=> ((JObject) a).Properties().FirstOrDefault(b=> (string)b.Value =="US\\East"))
.FirstOrDefault();

the pluses of this approuch are that you can use not only comparing but Contains, StartsWith, EndWith as well.

Upvotes: 2

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