How to handle null/empty values in JsonConvert.DeserializeObject

Question

I have the following code:

return (DataTable)JsonConvert.DeserializeObject(_data, (typeof(DataTable)));

Then, I tried:

var jsonSettings = new JsonSerializerSettings
{
    NullValueHandling = NullValueHandling.Ignore
};

return (DataTable)JsonConvert.DeserializeObject<DataTable>(_data, jsonSettings);

The return line is throwing the error:

{"Error converting value \"\" to type 'System.Double'."}

Lots of solutions online suggesting creating custom Class with nullable types but this won't work for me. I can't expect the json to be in a certain format. I have no control over the column count, column type, or column names.

Perhaps you should just use LINQ to JSON instead, and get a JObject instead of creating a DataTable? — Jon Skeet
– Jon Skeet, Commented Aug 4, 2015 at 15:22
If you need to convert DataTable use the dedicated converter DataTableConverter — Roland Mai
– Roland Mai, Commented Aug 4, 2015 at 15:26
Can you share an example of the JSON that is causing the problem? — dbc
– dbc, Commented Aug 4, 2015 at 15:42
@Candide Same error when using return JsonConvert.DeserializeObject<DataTable>(_data, new DataTableConverter()); — Kyle
– Kyle, Commented Aug 4, 2015 at 16:27

Thomas Hagström · Accepted Answer · 2016-03-17 10:32:06Z

264

You can supply settings to JsonConvert.DeserializeObject to tell it how to handle null values, in this case, and much more:

var settings = new JsonSerializerSettings
                    {
                        NullValueHandling = NullValueHandling.Ignore,
                        MissingMemberHandling = MissingMemberHandling.Ignore
                    };
var jsonModel = JsonConvert.DeserializeObject<Customer>(jsonString, settings);

answered Mar 17, 2016 at 10:32

Thomas Hagström

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4 Comments

iTrout Over a year ago

This is the perfect answer - I've been scouring solutions and finally one that works. Hero status.

Uylenburgh Over a year ago

MissingMemberHandling = MissingMemberHandling.Ignore is default. No need to add it.

Satheesh K Over a year ago

I got an error when deserializing the primitive type (long, int) properties in my class. The json comes from different api which i cannot control. The generic solution worked for me. Thank you Thomas

SendETHToThisAddress Over a year ago

imo these should be the default settings for the Deserializer. It shouldn't bug out and break your code by default just because a null value was encountered

Eynzhang · Accepted Answer · 2020-01-07 05:10:55Z

37

An alternative solution for Thomas Hagström, which is my prefered, is to use the property attribute on the member variables.

For example when we invoke an API, it may or may not return the error message, so we can set the NullValueHandling property for ErrorMessage:


    public class Response
    {
        public string Status;

        public string ErrorCode;

        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
        public string ErrorMessage;
    }


    var response = JsonConvert.DeserializeObject<Response>(data);

The benefit of this is to isolate the data definition (what) and deserialization (use), the deserilazation needn’t to care about the data property, so that two persons can work together, and the deserialize statement will be clean and simple.

edited Jan 7, 2020 at 5:10

answered Jan 7, 2020 at 4:02

Eynzhang

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1 Comment

Zimano Over a year ago

A downside of this, in my humble opinion, is that you couple a (fairly straightforward) data class to a specific library's implementation details. I guess it depends on your implementation.

DotNetHitMan · Accepted Answer · 2015-08-04 15:23:24Z

6

You can subscribe to the 'Error' event and ignore the serialization error(s) as required.

    static void Main(string[] args)
    {
        var a = JsonConvert.DeserializeObject<DataTable>("-- JSON STRING --", new JsonSerializerSettings
        {
            Error = HandleDeserializationError
        });
    }

    public static void HandleDeserializationError(object sender, ErrorEventArgs errorArgs)
    {
        var currentError = errorArgs.ErrorContext.Error.Message;
        errorArgs.ErrorContext.Handled = true;
    }

answered Aug 4, 2015 at 15:23

DotNetHitMan

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3 Comments

Kyle Over a year ago

This ignores the error all right. But the DataTable object returned is null.

DotNetHitMan Over a year ago

Can you post the JSON string and then i will alter my answer to better suit.

Adam Over a year ago

After trying everything else, and struggling with the absurdly bad "ArgumentNullException" which randomly occurs anywhere in 100,000s lines of JSON ... this was the first thing that worked. It's embarassing that JSON APIs are so bad at error reporting :(.

M Fuat · Accepted Answer · 2021-06-23 05:08:15Z

4

ASP.NET CORE: The accepted answer works perfectly. But in order to make the answer apply globally, in startup.cs file inside ConfigureServices method write the following:

    services.AddControllers().AddNewtonsoftJson(options =>
    {
        options.SerializerSettings.NullValueHandling = NullValueHandling.Ignore;
    });

The answer has been tested in a .Net Core 3.1 project.

edited Jun 23, 2021 at 5:08

answered Sep 1, 2020 at 11:47

M Fuat

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2 Comments

vivek86 Over a year ago

without context about what services you are accessing, the answer would be both incomplete and wrong.

ZXX Over a year ago

This is actually very good answer for contemporary code since the problem of setting global JSON deserialization options keeps surfacing up a lot.

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