CODEWITHSUNDEEP
c#json.net
Jessika Parker
Jessika Parker

Reputation: 189

How to ignore empty array elements with NewtonSoft library

I have the following code :

public City[] Cities { get; set; }

In City class, I have two properties

public string Name { get; set; }
public string Code { get; set; }

When a request comes that has this Cities field empty I would like to hide this with Newtonsoft.

[JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
public City[] Cities { get; set; }

But this code I have tried does not work because Cities is not null, but empty and the request always has the two properties in this array.

How should I use Newtonsoft in this case? Is there any additional check for the objects here needed?

Upvotes: 2

Views: 6492

Answers (1)

Ali Bahrami
Ali Bahrami

Reputation: 6073

You should use Conditional Property Serialization in JSON.NET. I think you are going to ignore this property if it's empty or null so, inside the class contains Cities properties add this method:

    // ignore a property on a condtion
    public bool ShouldSerializeCities() => Cities != null && Cities.Count > 0;

Update 1:

As @DavidG mentioned the workaround above won't ignore string fields (Name and Code) if they are null or empty. For making that happen you need to make use of DefaultValue:

Define JsonConvert settings like this:

        var settings = new JsonSerializerSettings {
            NullValueHandling = NullValueHandling.Ignore,
            DefaultValueHandling = DefaultValueHandling.Ignore
        };

Use DefaultValue attribute over your desiarred field/properties:

public class City
{
    [DefaultValue("")]
    public string Name
    {
        get;
        set;
    }

    [DefaultValue("")]
    public string Code
    {
        get;
        set;
    }
}

Serialize your object with the settings you created above:

JsonConvert.SerializeObject(obj, settings) ;

For example, if your object looks like this:

        var obj = new Foo{
            Cities = new  [] {
                new City() {Name = "A", Code = ""}
                , new City() {Name = "B", Code = "C"}
                , new City(){Name = "", Code = ""}
            }
        };

The result will be:

{
  "Cities": [
    {
      "Name": "A"
    },
    {
      "Name": "B",
      "Code": "C"
    },
    {}
  ]
}

I created a project on .NET Fiddle to see how it works.

If you don't like creating new settings, you still can use ShuldSerializeMemberName inside your City class:

public class City
{
   public string Name{get;set;}

   public bool ShouldSerializeName() => !string.IsNullOrEmpty(Name);
}

Upvotes: 7

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