.NET Core MVC Web API – control DateTime format in JSON output using JsonSerializerOptions

When creating API’s with .NET Core MVC, you can control the JSON output by adding JsonOptions to the controllers:

public void ConfigureServices(IServiceCollection services)
{
  ...
  ...
  services.AddControllers().AddJsonOptions();
  ...
  ...
}

This will ensure that when requesting application/json from a GET method, the format returned is JSON.

You can then add Converters to the configuration, controlling the default behavior of the JSON. This is a DateTime converter, forcing any DateTime type to be outputted as “2019-15-09Y22:30:00”

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

namespace MyCode.Converters
{
  public class DateTimeConverter : JsonConverter<DateTime>
  {
    public override DateTime Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
      return DateTime.Parse(reader.GetString());
    }

    public override void Write(Utf8JsonWriter writer, DateTime value, JsonSerializerOptions options)
    {
      writer.WriteStringValue(value.ToLocalTime().ToString("yyyy-MM-ddTHH:mm:ss"));
    }
  }
}

The converter needs to be added to my configuration:

public void ConfigureServices(IServiceCollection services)
{
  ...
  ...
  services.AddControllers().AddJsonOptions(options =>
    {
      options.JsonSerializerOptions.Converters.Add(new Converters.DateTimeConverter());
    }
  );
  ...
  ...
}

MORE TO READ:

• Create Web API’s with ASP.NET Core by Microsoft
• Setting JSON Serialization Configuration At Runtime On A .NET Core API by .NET Core Tutorials
• Try the new System.Text.Json APIs by Immo Landwerth