How to pass null value to nullable types in WebAPI

Question

I have a function as below:

        [HttpGet]
        [Route("Departments/{departmentid}/employeeByDeptId")]
        [ResponseType(responseType: typeof(IList<Employee>))]
        public HttpResponseMessage GetDetailsByDeptId(int departmentId, DateTime? sinceDate)
        {
            if (!ModelState.IsValid)
            {
                return Request.CreateErrorResponse(HttpStatusCode.BadRequest, ModelState);
            }

            var detailInfo = _employeeManager.GetDetailInfo(departmentId, sinceDate ?? _sinceDate);

            return CreateHttpResponseMessage(detailInfo);

        }

I have made sinceDate as Nullable type in declaration so that if null value is passed it takes the date which is there in '_sinceDate' variable declared locally. Now how can I pass null value to sinceDate parameter while making an API call.

When I pass below url: http://localhost:26754/v1/EmployeeMgnt/Departments/4/employeeByDeptId?sinceDate=2020-03-03

I get the desired result. Now I want to pass sinceDate as null. I tried http://localhost:26754/v1/EmployeeMgnt/Departments/4/employeeByDeptId?sinceDate=null http://localhost:26754/v1/EmployeeMgnt/Departments/4/employeeByDeptId?sinceDate isnull

All gave bad request error. Please tell how can I assign null value to sinceDate in API call?

simply deleting sinceDate from queryString is not working. I have to declare this sinceDate=null in function definition too. — kanika
– kanika, Commented Apr 6, 2020 at 12:58

Jerdine Sabio · Accepted Answer · 2020-04-06 13:10:33Z

2

Simply add parameterName = null in your route parameter.

public HttpResponseMessage GetDetailsByDeptId(int departmentId, DateTime? sinceDate = null){
}

Then in your request, you could just exclude that parameter and access with;

http://localhost:26754/v1/EmployeeMgnt/Departments/4/employeeByDeptId

Another option is add an overload. Have 2 function names receive different parameters.

public HttpResponseMessage GetDetailsByDeptId(int departmentId, DateTime sinceDate){
}

public HttpResponseMessage GetDetailsByDeptId(int departmentId){
}

edited Apr 6, 2020 at 13:10

answered Apr 6, 2020 at 12:21

Jerdine Sabio

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3 Comments

kanika Over a year ago

Thanks for this. But why I have to declare parameter = null when I have made sinceDate as Nullable type already

Jerdine Sabio Over a year ago

@kanika it's a precaution because there might be something yet to be setup in your controller and your controller is not accepting the parameters being sent. Adding a default value will immediately assign a null value if the key isn't found in your request parameters.

ruffin Over a year ago

At least for an int?, I'm getting 405 Method not allowed. 😕

carl-johan.blomqvist · Accepted Answer · 2021-06-11 07:19:09Z

1

For anyone reading this, as far as I can tell, the accepted answer doesn't work (in itself) anymore. See https://github.com/dotnet/aspnetcore/issues/6878#issuecomment-647830903 for more details and the 2 different alternative ways around it.

answered Jun 11, 2021 at 7:19

carl-johan.blomqvist

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