Return distinct collection attribute on AspNet Core API-CodePudding

I am new to Asp.Net Core and i am trying to build an API. I have the following model:

public class Location
{
    public string Country { get; set; }
    public string City { get; set; }
    public string Street { get; set; }
}

I have populated my database and a country has multiple Cities and the City has multiple streets. I have created an End-point to return all the countries from the database:

[HttpGet("countries")]
    public async Task<ActionResult<IEnumerable<string>>> GetCountries()
    {
        return await _context.Location.Select(x=>x.Country).Distinct().ToListAsync();
    }

This is returning and Array of string and i want it to return a the following JSON format response:

[
    {"country": "country1"},
    {"country": "country2"},
    ..........
    {"country": "countryN"}
]

My second end point is to retrieve all the cities from for a specific country :

 [HttpGet("cities/{country}")]
    public async Task<ActionResult<IEnumerable<string>>> GetCites(string country)
    {
        --------- Missing code ------
    }

I have tried different options but i managed only to get array of string for both endpoints. I Have tried to replace the IEnumerable by IEnumerable, but without results.

CodePudding user response：

For the first api, create a model:

public class CountryResponse
{
    public string Country { get; set; }
}

And use this model class in the return type of the API, and return the result as:

[HttpGet("countries")]
public async Task<ActionResult<IEnumerable<CountryResponse>>> GetCountries()
{
     return await _context.Location.Select(x => new CountryResponse{ Country = x.Country }).Distinct().ToListAsync();
}

Similarly for the second API, create a response model:

public class CityResponse
{
   public string City { get; set; }
}

And the API will look like

[HttpGet("cities/{country}")]
public async Task<ActionResult<IEnumerable<CityResponse>>> GetCites(string country)
{
    return await _context.Location.Where(x => x.Country == country).Select(x => new CityResponse { City = x.City }).ToListAsync();
}

CodePudding user response：

The line

_context.Location.Select(x=>x.Country).Distinct().ToListAsync()

Returns a list of strings, so that is what the ActionResult will return. The easiest way to get it into the format you want is to return a KeyValuePair. If you changed the return to this, it should work.

return await _context.Location.Select.Distinct().Select(country => new KeyValuePair<string, string>("country", country)).ToList()

Same idea with the cities, just put them into a KeyValuePair and you should get what you need.