c# System.Text.Json custom EnumJsonConverter

Question

I have a problem. In our project the backend developers used different Enums then we did in our project, and we got a problem. We now need to serialize our object for them, changing will result for us rewrite the whole UI in .NET MAUI, so we want that to avoid. I am interested is there a way to write a custom Json Converter for System.Text.Json.

Here is my example:

public enum RenovationMode : byte
{
    [Description("Beams")]
    RoofTruss,

    [Description("Slats")]
    RoofTiles,

    [Description("RoofStructure")]
    CompleteRoofStructureReplacement,

    [Description("Waterproofing")]
    Waterproofing
}

So my idea was to put on every Enum value as description the value that is needed on server side as string (because they asked it as string). But, in converter I can't figure out how to read that.

public class EnumMapperJsonConverter : JsonConverter<string>
{
    public override string Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        throw new NotImplementedException();
    }

    public override void Write(Utf8JsonWriter writer, string value, JsonSerializerOptions options)
    {
        //how to read here the from the Enum the Description and return it as a string ?
    }
}

Is this the right way to do this?

Answer 1

This code works for me

    var myClass = new MyClass { Mode = RenovationMode.RoofTiles };

    var json = System.Text.Json.JsonSerializer.Serialize(myClass);

output

{"Mode":"Slats"}

classes

public class MyClass
{
[System.Text.Json.Serialization.JsonConverter(typeof(EnumMapperJsonConverter))]
public RenovationMode Mode { get; set; }
}

public class EnumMapperJsonConverter : System.Text.Json.Serialization.JsonConverter<RenovationMode>
{
    public override RenovationMode Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        throw new NotImplementedException();
    }

    public override void Write(Utf8JsonWriter writer, RenovationMode value, JsonSerializerOptions options)
    {
        writer.WriteStringValue(GetEnumDescription(value));
    }
}
public static string GetEnumDescription(Enum value)
{
    if (value == null) { return ""; }

    DescriptionAttribute attribute = value.GetType()
            .GetField(value.ToString())
            ?.GetCustomAttributes(typeof(DescriptionAttribute), false)
            .SingleOrDefault() as DescriptionAttribute;
    return attribute == null ? value.ToString() : attribute.Description;
}