Question

I am trying to parse the JSON incrementally, i.e. based on a condition.

Below is my json message and I am currently using JavaScriptSerializer to deserialize the message.

string json = @"{"id":2,
"method":"add",
"params":
   {"object":
       {"name":"test"
        "id":"1"},
        "position":"1"}
  }";

JavaScriptSerializer js = new JavaScriptSerializer();
Message m = js.Deserialize<Message>(json);

Message class is shown below:

 public class Message
 {
        public string id { get; set; }
        public string method { get; set; }
        public Params @params { get; set; }
        public string position { get; set; }
 }
public class Params
{
        public string name { get; set; }
        public string id{ get; set; 
}

The above code parses the message with no problems. But it parses the entire JSON at once. I want it to proceed parsing only if the “method” parameter’s value is “add”. If it is not “add”, then I don’t want it to proceed to parse rest of the message. Is there a way to do incremental parsing based on a condition in C#? (Environment: VS 2008 with .Net 3.5)

Answer 1

I have to admit I’m not as familiar with the JavaScriptSerializer, but if you’re open to use JSON.net, it has a JsonReader that acts much like a DataReader.

using(var jsonReader = new JsonTextReader(myTextReader)){
  while(jsonReader.Read()){
    //evaluate the current node and whether it's the name you want
    if(jsonReader.TokenType.PropertyName=="add"){
      //do what you want
    } else {
      //break out of loop.
    }
  }
}