Aspnetcore 1.1 group by and count gets an object

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I have the following table:

<pre lang="c++">Cans
 
Id: int 
HospitalId: (Foreign Key) int 
operDt: DateTime

I need to calculate the total number of cans rows grouped by hospitalId

to get a similar result without Id

screenshot[^]

What I have tried:

The repository :

C++

public Task GetCansMin(DateTime startdt, DateTime enddt)
            {
                using (appContext)
                {
                    return appContext.Cans.Where(c => c.OperDt > startdt && c.OperDt < enddt).GroupBy(c => c.HospitalId)
                          .Select(g => new
                          {
                              NumberofCancelled = g.Count() 
                          }).ToArrayAsync();
                         
                };
            }

The controller:

C++

[HttpGet("bydate")]
            public IActionResult GetCanMin(DateTime startdt, DateTime endd)
            {
                var res = this._unitOfWork.Cans.GetCansMin(startdt, endd);
                return Ok(res);
            }

When passing the request with postman:

C#

http://localhost:56964/api/cansdatas/bydate?startdt=2016-01-01&enddt=2016-12-31

instead of receiving an array of results I get an empty object....
Could you help?

Posted 4-Nov-17 7:15am

walid youssef

Updated 6-Nov-17 7:06am

Karthik_Mahalingam

v3

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Richard Deeming · Answer 1 · 2017-11-06T07:06:00

You're returning a Task, rather than the results of that Task.

You're also disposing of the DbContext before the Task has completed.

(There's also a missing "t" in the action parameter name, but I'm not sure whether that's just a typo in your question.)

Try something like this:

C#

public async Task<object> GetCansMin(DateTime startdt, DateTime enddt)
{
    using (appContext)
    {
        return await appContext.Cans
            .Where(c => c.OperDt > startdt && c.OperDt < enddt)
            .GroupBy(c => c.HospitalId)
            .Select(g => new
            {
                NumberofCancelled = g.Count() 
            })
            .ToArrayAsync();
                         
    }
}

[HttpGet("bydate")]
public async Task<IActionResult> GetCanMin(DateTime startdt, DateTime enddt)
{
    var res = await this._unitOfWork.Cans.GetCansMin(startdt, enddt);
    return Ok(res);
}

NB: Since you're storing the DbContext in a field, I'd be inclined to remove the using (appContext) blocks from your methods, and have your unit-of-work class implement IDisposable instead. You can then register that class to be disposed after each request:
Four ways to dispose IDisposables in ASP.NET Core[^]