local rest api controller does not receive data from repository function-call - rest

Question

Our VS-2022 development project is Blazor WASM Core-6 with local REST-API for data. Using Postman, my testing is not getting data from the controller call to a repository function -- using breakpoints and local debugging -- as one would expect.
The repository function return statement is return Ok(vehicleTrips);. The IEnumerable vehicleTrips data variable contains the correct four records as expected from the DB fetch.
From the controller the call to the repository function is:
var result = (await motripRepository.GetMOTripsByDateRange((int)eModelType.Vehicle, pVehicleList, pDateFrom, pDateTo)!)!;
The controller function signature is:
[HttpGet("byDateRange/{pVehicleList}/{pDateFrom}/{pDateTo}")]
[ActionName(nameof(GetVehicleMOTripsByDateRange))]
public async Task<ActionResult<IEnumerable<MOTRIP>>> GetVehicleMOTripsByDateRange([FromRoute] string pVehicleList, [FromRoute] string pDateFrom, [FromRoute] string pDateTo) {
This is my problem. The result return value from the repository has a return.Value of null -- NOT four trip records as we should.
Additionally, the VS-Studio's 'local'-debugger shows that there are other properties of return such as .Return and .Return.Value.Count as 4 (four).
My question is "what could be causing this"? All of my other rest-api calls and controller calls with Postman work correctly as one would expect.
Did I select the wrong type of "controller" from Visual-Studio? I am not experienced at all in coding classic MVC web-applications. VS-Blazor offer a number of controller-types. In the past, I "copied" a working controller and "changed the code" for a different "model".
Your assistance is welcome and appreciated. Thanks...John

Answer 1

I found out what actually happened to cause the result.Value is null and had nothing to do with the controller-type -- it was in the interpretation of the return value from the repository function.
I found an SO link Get a Value from ActionResult<object> in a ASP.Net Core API Method that explains how to respond to a ActionResult<objecttype> return value in the reply/answer section with the word "actual" is first defined. You will see this word "actual" in my revised code below.
My revised code is posted here with comments both inside the code section and below the code section. My comment inside the code begins with "<==" with text following until "==>"
// Initialize.
MOTRIP emptyMoTrip = new MOTRIP();
MOTRIP? resultMoTrip = new MOTRIP();
IEnumerable<MOTRIP> allTrips = Enumerable.Empty<MOTRIP>();
int daysPrevious = (int)(pTripType == eTripType.Any ? eDateRangeOffset.Week : eDateRangeOffset.Month);
// convert DateRangeOffset to 'dateonly' values.
DateOnly dtTo = DateOnly.FromDateTime( DateTime.Today);
DateOnly dtFrom = dtTo.AddDays(daysPrevious);
// Fetch the vehicle trips by date-range.
var result = await GetVehicleMOTripsByDateRange(UID_Vehicle.ToString(), dtFrom.ToString(), dtTo.ToString());
if ((result.Result as OkObjectResult) is null) { **<== this is the fix from the SO link.==>**
return StatusCode(204, emptyMoTrip);
}
var statusCode = (result.Result as OkObjectResult)!.StatusCode;
if (statusCode==204) {
return StatusCode(204, emptyMoTrip);
}
**<== this next section allows code to get the result's DATA for further processing.==>**
var actual = (result.Result as OkObjectResult)!.Value as IEnumerable<MOTRIP>;
allTrips = (IEnumerable<MOTRIP>)actual!;
if ((allTrips is not null) && (!allTrips.Any())) {
return StatusCode(204, emptyMoTrip);
}
<== this next section continues with business-logic related to the result-DATA.==>
if (allTrips is not null && allTrips.Any()) {
switch (blah-blah-blah) {
**<== the remainder of business logic is not shown as irrelevant to the "fix".==>**
Please use browser search for "<==" to find my code-comments.
Please use browser search for "actual" and "OkObjectResult" to see the relevant code fix sentences.