IsoDateTimeConverter added to .NET API breaks default model binding

Question

I was having an issue with my .NET Core API where when DateTimes were serializes, it would leave off milliseconds if the value was 0. This question explains the issue. I added the following to my .NET Core Startup class and it resolved the issue such that when I did a GET, all dates would be formatted correctly:

services.AddMvc()
    .AddJsonOptions(options =>
    {
        var settings = options.SerializerSettings;
        var dateConverter = new IsoDateTimeConverter
        {
            DateTimeFormat = "yyyy'-'MM'-'dd'T'HH':'mm':'ss.fff"
        };
        settings.Converters.Add(dateConverter);
    });

After implementing this, I found that it broke default model bindings elsewhere. For example, I have a POST endpoint that accepts the following viewmodel:

public class PatientRegistrationViewModel
{
    public DateTime DateOfBirth { get; set; }
}

Previously I was passing the following JSON data in the request body which it bound successfully:

{
    dateOfBirth: '1981-04-18'
}

After implementing the date converter above, the viewmodel equals null in my controller.

Did you maybe just forget the `'Z'` at the end of the `DateTimeFormat` string? — haindl, Mar 22 '17 at 17:40

score 1 · Accepted Answer · answered Mar 25 '17 at 20:37

One quick solution is to introduce and use WriteOnlyIsoDateTimeConverter:

public class WriteOnlyIsoDateTimeConverter : IsoDateTimeConverter
{
    public override bool CanRead { get { return false; } }
}

By overriding CanRead to return false, the model binder should continue to use the currently built-in date parsing while using the converter for output formatting.

Another option might be to replace the JsonOutputFormatter as shown in this question.

`WriteOnlyIsoDateTimeConverter` FTW! – mellis481 Mar 27 '17 at 13:00 — mellis481, Mar 27 '17 at 13:00

IsoDateTimeConverter added to .NET API breaks default model binding

1 Answers1