Harmonization to parse DateTime from query/body

[vernou]

I noticed some difference when a DateTime is parsed from query or body.

See this controller as demo :

[Route("datetime")]
[ApiController]
public class DateTimeController : ControllerBase
{
    [HttpGet]
    public string Get(DateTime dateTime) => $"{dateTime} {dateTime.Kind}";

    [HttpPost]
    public string Post(DtoWihDateTime dto) => Get(dto.Value);
}

public class DtoWihDateTime
{
    public DateTime Value { get; set; }
}

When the timezone is unspecified, it's the same result :

GET http://localhost:5088/datetime?datetime=2023-01-01T15:00:00
# Response
# 01/01/2023 15:00:00 Unspecified

###

POST http://localhost:5088/datetime
Content-Type: text/json

{ "Value": "2023-09-01T15:00:00" }
# Response
# 01/09/2023 15:00:00 Unspecified

When the timezone is specified with "Z" (UTC denominator), it's the same result :

GET http://localhost:5088/datetime?datetime=2023-01-01T15:00:00Z
# Response
#01/01/2023 15:00:00 Utc

###

POST http://localhost:5088/datetime
Content-Type: text/json

{ "Value": "2023-09-01T15:00:00Z" }
# Response
# 01/09/2023 15:00:00 Utc

But when the timezone is specified with UTC offset, the result differ :

GET http://localhost:5088/datetime?datetime=2023-01-01T15:00:00%2B00
# Response
# 01/01/2023 15:00:00 Utc

###

POST http://localhost:5088/datetime
Content-Type: text/json

{ "Value": "2023-09-01T15:00:00+00" }
# Response
# 01/09/2023 17:00:00 Local

---

This difference come from the parsing method.

When DateTime is passed by query, then DateTimeModelBinder use DateTime.Parse with DateTimeStyles.AdjustToUniversal.

When DateTime is passed by body, then DateTimeConverter use a custom method specific to System.Text.Json

---

I know it's possible to defined custom binder/converter, but I think a more homogeneous behavior would be easier to understand for a newbie.