Using a database function with entity framework

Question

I'm working on a new website that's using entity framework.

Using code from another site, that was linq to sql, I have a database function to calculate distance from one set of latitude and longitude to another set. And the function returns a decimal with the distance.

I've added to my identitymodel.cs in the ApplicationDbContext class:

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
    public ApplicationDbContext()
        : base("DefaultConnection", throwIfV1Schema: false)
    {
    }

    public static ApplicationDbContext Create()
    {
        return new ApplicationDbContext();
    }
 public ObjectResult<int> getDistance(string lat1, string lon1, string lat2, string lon2)
    {
        var params1 = new[] {
            new ObjectParameter("lat1", lat1),
            new ObjectParameter("lon1", lon1),
            new ObjectParameter("lat2", lat2),
            new ObjectParameter("lon2", lon2)
        };                

        return ((IObjectContextAdapter)this).ObjectContext.ExecuteFunction<int>("LatLonRadiusDistance", params1);
    }
}

And this is my query:

var datap = (from p in db.table
                     where db.LatLonRadiusDistance(data.lat, data.lon, p.platitude, p.plongitude) <= 10
                     select new latlon
                     {
                         lat = p.property_lat,
                         lon = p.property_lon,
                         address = p.property_address,
                         id = p.property_id,
                         count = ecount
                     }).Take(500);

However now I'm getting an error:

The FunctionImport 'LatLonRadiusDistanceVarchar' could not be found in the container 'ApplicationDbContext'.

What am I doing wrong?

Answer 1

If you are using EF 4.1 and above, change "ObjectParameter" to "SqlParameter" and "ExecuteFunction" to "ExecuteStoreQuery" in your Context.cs file.

The "ExecuteStoreQuery" method also expects you to add the parameter names in-front of the stored proc. Find example below.

    var param1Parameter = param1 != null ?
    new SqlParameter("param1", param1) :
    new SqlParameter("param1", typeof(string));

    var param2Parameter = param2 != null ?
    new SqlParameter("param2", param2) :
    new SqlParameter("param2", typeof(int));

    return ((IObjectContextAdapter)this).ObjectContext.ExecuteStoreQuery<sp_TestSproc_Result>("sp_TestSproc @param1, @param2", param1Parameter, param2Parameter);