如何在webAPI方法中获取表的特定列

Question

I have a MVC4 application with a WebApi method which is getting entire table data from database. Now i want to extract only two columns from it. How can I do it?

I know that arrays will be used to do so but don't know the syntax in .net. This is my WebAPi function which is getting the entire table data from the SQL server database:

namespace BRDCEP_MIS.Areas.BRDCEP.Controllers
{
    public class WebApiController : ApiController
    {

        //api get method.

        //[Route("WebApi/GetPscTargets")]

        public HttpResponseMessage Get() {
            using (ApplicationDbContext db = new ApplicationDbContext())
            {

                List<PscDistrictTargets> xx = new List<PscDistrictTargets>();
                xx = db.PscDistrictTargetss.ToList();
                //xx.ID = Convert.ToString(DATA);
                HttpResponseMessage response = new HttpResponseMessage();
                response = Request.CreateResponse(HttpStatusCode.OK, xx);
                return response;
            }

        }

    }
}

Answer 1

You can use the Select method and do a projection on only those properties you needed to an an object of your DTO/view model to represent this data, in your LINQ query.

So create a DTO class to represent the data you want with only those properties,

public class MyDto
{
    public int TargetId { set; get; }
    public string TargetName { set; get; }
}

Now update your LINQ query use the Select method to get only those properties and project those our dto object.

var items = db.PscDistrictTargetss
              .Select(f => new MyDto { TargetName = f.Name, 
                                       TargetId = f.Id})
              .ToList();
return Request.CreateResponse(HttpStatusCode.OK, items );

Assuming PscDistrictTargets entity class has a Name and Id property. Update that part based on your actual property names.