ASP.NET Core 8 Web API - JsonConverter<DateTime> incorrectly converts DateTime

Question

We have an ASP.NET Core 8 WEB API application which uses traditional N-layer architecture.

A repository returns a JSON array:

string jsonArray = "[ 
    { 
        "id": 1,
        "createDate": "2024-05-30T15:46:45"
    }
        
]"

The model of this JSON looks like this:

public class FooBar
{
    public int Id { get; set; }
    public DateTime CreateDate { get; set; }
}

Having read this post, I have written the following converter:

public class DateTimeJsonConverter : JsonConverter<DateTime>
{
    public override DateTime Read(
        ref Utf8JsonReader reader,
        Type typeToConvert,
        JsonSerializerOptions options) 
    {
            if (typeToConvert == typeof(DateTime))
            {
                return DateTimeHelper.Parse(reader.GetString());
            }
            
            throw new ArgumentException("It is not a datetime");
    }

    public override void Write(
        Utf8JsonWriter writer,
        DateTime value,
        JsonSerializerOptions options)
    {
            var utcFormat = value.Kind == DateTimeKind.Utc ? "'Z'" : string.Empty;
            writer.WriterStringValue(value.ToString($"yyyy-MM-dd'T'HH:mm:ss{utcFormat}", 
                CultureInfo.InvariantCulture));
    }
}

And I add it like this:

jsonSerializerOptions.Converters.Add(new DateTimeJsonConverter());

However, when the converter is called then the value shows the incorrect date:

I believe it should have "2024-05-30T15:46:45" value, but it shows "1/1/0001 12:00:00 AM".

Can you tell me what I am doing wrong? Am I missing something? My goal is to read JSON from the database and send it to React application. We are using System.Text.Json library.

Answer 1

Your JSON is in the camel case. By default, PropertyNameCaseInsensitive is false.

Either set PropertyNameCaseInsensitive to true in JsonSerializerOptions instance

jsonSerializerOptions.PropertyNameCaseInsensitive  = true;

or setting PropertyNamingPolicy to JsonNamingPolicy.CamelCase.

jsonSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;