Passing DateTimeOffset as WebAPI query string

Question

I've got a WebAPI action that looks like so:

[Route("api/values/{id}")]
public async Task<HttpResponseMessage> Delete(string id, DateTimeOffset date) {
    //do stuff
}

But when I invoke this from a HttpClient instance, making a URL like:

string.Format("http://localhost:1234/api/values/1?date={0}", System.Net.WebUtility.UrlEncode(DateTimeOffset.Now.ToString()));
// -> "http://localhost:1234/api/values/1?date=17%2F02%2F2015+7%3A18%3A39+AM+%2B11%3A00"

I get a 400 response back saying that the non-nullable parameter date does not exist.

I've also tried adding the [FromUri] attribute to the parameter but it still doesn't map through. If I change it to be DateTimeOffset? I can see it is left as null and looking at Request.RequestUri.Query the value is there, just not mapped.

Finally I tried not doing a WebUtility.UrlEncode and it made no different.

Answer 1

Answer

To send a DateTimeOffset to your API, format it like this after converting it to UTC:

2017-04-17T05:04:18.070Z

The complete API URL will look like this:

http://localhost:1234/api/values/1?date=2017-04-17T05:45:18.070Z

It’s important to first convert the DateTimeOffset to UTC, because, as @OffHeGoes points out in the comments, the Z at the end of the string indicates Zulu Time (more commonly known as UTC).

Code

You can use .ToUniversalTime().ToString(yyyy-MM-ddTHH:mm:ss.fffZ) to parse the DateTimeOffset.

To ensure your DateTimeOffset is formatted using the correct timezone always use .ToUniversalTime() to first convert the DateTimeOffset value to UTC, because the Z at the end of the string indicates UTC, aka "Zulu Time".

DateTimeOffset currentTime = DateTimeOffset.UtcNow;
string dateTimeOffsetAsAPIParameter = currentDateTimeOffset.ToUniversalTime().ToString("yyyy-MM-ddTHH:mm:ss.fffZ");
string apiUrl = string.Format("http://localhost:1234/api/values/1?date={0}", dateTimeOffsetAsAPIParameter);

Answer 2

The problem is the + (plus) char in the offset part, we should encode that.

If the offset is - (minus) no need to encode

Encoded value of +(plus) is %2B So the 2021-05-05T18:00:00+05:00 should be passed as 2021-05-05T18:00:00%2B05:00

http://localhost:1234/api/values/1?date=2021-05-05T18:00:00%2B05:00

if the offset is - (minus) then

http://localhost:1234/api/values/1?date=2021-05-05T18:00:00-05:00