CommandSerializer.cs

using System;
using Newtonsoft.Json;

public class Program
{
    public static void Main()
    {
        var info = new Info { Some = "a", Field = 1 };
        info.GetCommandJson<AddOrUpdateChat>();
    }
}
public class Info
{
    public string Some { get; set; }
    public int Field { get; set; }

    public Info() { }
}
public class BaseCommand
{
    public string Data { get; set; }
}
public class AddOrUpdateChat : BaseCommand { }

public static class CommandExtentions
{
    public static string GetCommandJson<T>(this object toCommand) where T : BaseCommand, new()
    {
        var serialized = JsonConvert.SerializeObject(toCommand);
        var command = new T()
        {
            Data = serialized
        };
        return JsonConvert.SerializeObject(command);
    }
}