C# asp.net 核心 webapi 抛出“JSON 值无法转换为 System.Nullable`1[System.DateTime]

Question

I have a asp.net core webapi with class property DateTime? DateofBirth. The front end is sending the date of birth as a string in the format. "MM/dd/yyyy". I dont want to change the C# property with string type. Is there a better solution to handle this?

public class Entity
{
    public Guid Id { get; set; }

    [Required(ErrorMessage = "FirstName must be supplied")]
    public string FirstName { get; set; }

    [Required(ErrorMessage = "Surname must be supplied")]
    public string Surname { get; set; }
    
    public DateTime? DateOfBirth { get; set; }
}

POSTMAN request:

{
    "dateOfBirth": "07/07/2020",
    "surname": "Martin",
    "id": "ae8d7edf-23b6-498b-865d-9840ce401b19",
    "firstName": "Robert",
}

Error:

{
    "type": "https://tools.ietf.org/html/rfc7231#section-6.5.1",
    "title": "One or more validation errors occurred.",
    "status": 400,
    "traceId": "|4dd4b26-4340be36ab0c62cc.",
    "errors": {
        "$.dateOfBirth": [
            "The JSON value could not be converted to System.Nullable`1[System.DateTime]. Path: $.dateOfBirth | LineNumber: 2 | BytePositionInLine: 31."
        ]
    }
}

Answer 1

The error is because by default System.Text.Json library parses the value from JSON according to the ISO 8601:-2019 extended profile.

Two ways to handle it:

1. Change the request of your front end from MM/DD/YYYY to YYYY-MM-DD . (This is ISO 8601 compliant)
2. Implement custom converter according to this documentation by Microsoft .