如何使用Newtonsoft.Json反序列化时忽略类型

Question

I am trying to Deserialize json data which i have to with respect to model class i have

Json :

"{'test':'1339886'}"

Classes :

public class NewtonTest
    {
        public Element test { get; set; }
    }
public class Element
    {
        public string sample { get; set; }
    }

In Main class :

//under Main
string jsonData =  "{'test':'1339886'}";
var  = JsonConvert.DeserializeObject<NewtonTest>(jsonData);

Error Info : //innner exception

Could not cast or convert from System.String to Test.Element."

I am completely aware of what the error states as i am passing string in my json where as in class i have a class as type(mismatch happening) .

In such cases i need to handle the error and maybe place a null if there is mismatch in output but it should not throw exception .

I tried my best reading the docs and setting options via settings but none seem to work .

I am using version 4.5 of Newtonsoft.Json

Answer 1

You can tell JSON.NET to ignore errors for specific members and types:

var settings = new JsonSerializerSettings
{
    Error = (sender, args) => 
    {
        if (object.Equals(args.ErrorContext.Member, "test") && 
            args.ErrorContext.OriginalObject.GetType() == typeof(NewtonTest))
        {
            args.ErrorContext.Handled = true;
        }
    }
};

NewtonTest test = JsonConvert.DeserializeObject<NewtonTest>(json, settings);

This code won't throw an exception. The Error handler in the settings object will get called and if the member throwing the exception is named "test" and belongs to NewtonTest , the error gets skipped over and JSON.NET keeps going.

The ErrorContext property also has other properties that you might want to leverage to only handle errors that you're absolutely sure you want to ignore.

Answer 2

If you want a work around while using the badly formed json data. Here is a simple solution that works.

 public static class NewtonHelpers
{
    internal class NewtonHelper
    {
        public string test { get; set; }
    }

    public static NewtonTest BuildNewton(string jsonData)
    {
        var newtonHelper = JsonConvert.DeserializeObject<NewtonHelper>(jsonData);

        var newtonTest = new NewtonTest { test = { sample = newtonHelper.test } };

        return newtonTest;
    }
}

Which can be used like

var testdata = "{'test':'1339886'}";
var newNewton = NewtonHelpers.BuildNewton(testdata);