How to ignore JSON serialization of constant properties using System.Text.Json?

Question

I am trying to migrate from Newtonsoft.Json to System.Text.Json. "[Newtonsoft.Json.JsonIgnore]" works for ignoring the constant property during serialization, but "[System.Text.Json.Serialization.JsonIgnore]" does not. I wonder if there is a work around.

So I am trying to migrate from;

using Newtonsoft.Json;

public class MyClass: MyBaseClass
{
    [JsonIgnore]
    public const string MyConstString = "lets get rid of netwonsoft dependency";

    public string data;

    public String(string data)
    {
        this.data = data;
    }
}

to;

using System.Text.Json.Serialization;

public class MyClass: MyBaseClass
{
    [JsonIgnore] // Error
    public const string MyConstString = "lets get rid of netwonsoft dependency";

    public string data;

    public String(string data)
    {
        this.data = data;
    }
}

The error description is; "Attribute 'JsonIgnore' is not valid on this declaration type. It is only valid on 'property, indexer' declarations."

Is it because System.Text.Json does not support such use of JsonIgnore, or am I missing something? I could not find anything useful on this link regarding this issue. Would you have any ideas?

a property declaration usually has a getter and/or a setter. Can you try changing it to public string MyConstString { get; } = "your string"; — stjns
– stjns, Commented Mar 4, 2020 at 15:54
System.Text.Json won't serialise a const anyway, you don't need that attribute here. — DavidG
– DavidG, Commented Mar 4, 2020 at 15:56
In fact neither will Newtonsoft, it's not clear why you have this attribute on your const in the first place? — DavidG
– DavidG, Commented Mar 4, 2020 at 15:57
Perhaps a bigger problem you have is that the new serialiser doesn't serialise fields, meaning you need to change them to properties. — DavidG
– DavidG, Commented Mar 4, 2020 at 16:02
Newtonsoft will only serialise const values if you explicitly mark them with the [JsonProperty] attribute. — DavidG
– DavidG, Commented Mar 4, 2020 at 16:08

DavidG · Accepted Answer · 2020-03-04 16:44:29Z

The JSON.Net [JsonIgnore] attribute has it's usage set to AttributeTargets.Property | AttributeTargets.Field meaning it can be used on a const. However the new .NET Core API version of [JsonIgnore] is set to AttributeTargets.Property only. That means you can only use it on a property.

Having said that, JSON.Net will not serialise const values unless you explicitly tell it to serialise by using a [JsonProperty] attribute, which then makes adding another attribute to ignore it a little peculiar anyway.

For example, JSON.Net will serialise the class you have in your question as:

{"data":"foo"}

Whereas the serialiser in System.Text.Json will give you this:

{}

So another problem is that the newer API doesn't serialise fields. The takeaway from this is that you should be using modern C# techniques, and that means using properties, for example:

public string data { get; set; }

Collectives™ on Stack Overflow

How to ignore JSON serialization of constant properties using System.Text.Json?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related