How to serialize to strings only

Question

I would like the output of serialization of properties of an object to be strings, even if they are int properties or bool properties.

using System;
using System.Text.Json;

public class Program
{
    public static void Main()
    {
        var myObj = new MyObj();
        var result = JsonSerializer.Serialize(myObj);
        Console.WriteLine(result); 
    }       
}

public class MyObj
{
    public MyObj()
    {
        Version = 10;
    }
    public int Version {get;set;}   
}

The above outputs

{ "Version" : 10 }

I'd like it to output

{ "Version" : "10" }

Changing the Version type in MyObj to an int creates an exception

Before I change the Version to a string, and save the number as a string (eg Version = "10";), is this achievable via the serialization process?

Answer 1

Here's an example of using a custom converter on the class level:

using System;
using System.Text.Json;
using System.Text.Json.Serialization;

                    
public class Program
{
    public static void Main()
    {
        var m = new MyObj();
        Console.WriteLine(System.Text.Json.JsonSerializer.Serialize(m));
    }
}

[JsonConverter(typeof(MyObjConverter<MyObj>))]
public class MyObj
{
    public MyObj()
    {
        Version = 10;
        Data = "Test";
        IsTrue = false;
        
    }
    public int Version {get;set;}
    public string Data {get; set;}
    public bool IsTrue {get; set;}
    public bool? IsFalse {get; set;} = null;
    public MyObj2 MyO2 {get; set;} = new MyObj2 { Age = 30, IsOld = false };
}

[JsonConverter(typeof(MyObjConverter<MyObj2>))]
public class MyObj2
{
    public int Age {get; set;} = 2;
    public bool IsOld {get; set;} = true;
}


public class MyObjConverter<T> : JsonConverter<T>
{
        public override T Read(
            ref Utf8JsonReader reader,
            Type typeToConvert,
            JsonSerializerOptions options) =>
                throw new NotImplementedException();

        public override void Write(
            Utf8JsonWriter writer,
            T myObj,
            JsonSerializerOptions options)
        {
            writer.WriteStartObject();
            foreach(var prop in myObj.GetType().GetProperties())
            {
                if(prop.PropertyType == typeof(Boolean) || prop.PropertyType == typeof(int))
                {
                    writer.WriteString(prop.Name, prop.GetValue(myObj, null)?.ToString().ToLower());
                }
                else
                {
                    writer.WritePropertyName(prop.Name);
                    writer.WriteRawValue(System.Text.Json.JsonSerializer.Serialize(prop.GetValue(myObj, null), options));
                }
            }
            writer.WriteEndObject();        
        }
}

DotNet Fiddle