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.

Solution 1

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);

Solution 2

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.

Solution 3

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;
    }

Comments

[Jon Skeet]

Perhaps you should just use LINQ to JSON instead, and get a JObject instead of creating a DataTable?

[dbc]

Can you share an example of the JSON that is causing the problem?

[Kyle]

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

[DotNetHitMan]

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

[iTrout]

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

[Saskia]

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

[Satheesh K]

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

[vivek86]

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

[SendETHToThisAddress]

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

[M Fuat]

@vivek86 I have updated the answer. You can remove your downvote.

[ZXX]

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