How to exclude a null property from JSON result when not using Json.Net?

Question

I'm developing an ASP.NET Core web API, without EntityFrameworkCore, that uses controller classes for implementing the HTTP actions, and that generally follows this pattern:

public class MyItem
{
    public string Prop1 { get; set; }
    public MyOtherItem? OtherItem { get; set; }
}

public IEnumerable<MyItem> GetMyItems()
{
    List<MyItem> myItems = new();

    // Fill in myItems with stuff where OtherItem is sometimes null

    return myItems;
}

public class MyController : ControllerBase
{
    [HttpPost]
    public Task<IEnumerable<MyItem>> FetchMyItems()
    {
        var myItems = GetMyItems();

        return Task.FromResult(myItems);
    }
}

On making the POST request to FetchMyItems in Postman, the response is a JSON string containing an array of MyItem objects like this:

[
    {
        "prop1": "a string",
        "otherItem": {
            "otherprop1": "a string",
            "otherprop2": 0
        }
    },
    {
        "prop1": "a string",
        "otherItem": null
    }
]

What I would like is for the OtherItem property to be excluded if it is null. I have looked at adding the [JsonProperty(NullValueHandling=NullValueHandling.Ignore)] attribute to the class but that has no effect, probably because whatever process is happening in FromResult() is not using the JsonSerializer.

Is there a different property attribute I can use? Or do I have to alter my action to use JsonSerializer?

See stackoverflow.com/questions/74103427/…

kodbuse
– kodbuse

2022-10-17 21:57:44 +00:00
Commented Oct 17, 2022 at 21:57 — kodbuse
– kodbuse, Commented Oct 17, 2022 at 21:57

Ibrahim Timimi · Accepted Answer · 2022-10-17 22:17:32Z

4

You can add the ignore null property condition when adding the controller. This uses System.Text.Json and not Newtonsoft library.

For .NET 5 and above:

builder.Services.AddControllers()
    .AddJsonOptions(opt =>
    {
        opt.JsonSerializerOptions.DefaultIgnoreCondition = 
            JsonIgnoreCondition.WhenWritingNull;
    });

For .NET Core 3.1:

services.Services.AddControllers()
    .AddJsonOptions(options =>
    {
        options.JsonSerializerOptions.IgnoreNullValues = true;
    });

edited Oct 17, 2022 at 22:17

answered Oct 17, 2022 at 21:54

Ibrahim Timimi

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1 Comment

SiBrit Over a year ago

Going into the Program.cs and altering the AddControllers to ignore nulls was the cleanest approach without me need to fundamentally alter my code. Thanks.

burak ramazan · Accepted Answer · 2022-10-17 21:37:26Z

0

You can use like this:

string json = JsonConvert.SerializeObject(myItems, Newtonsoft.Json.Formatting.Indented, new JsonSerializerSettings { NullValueHandling = NullValueHandling.Ignore });

answered Oct 17, 2022 at 21:37

burak ramazan

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