Additional information: No mapping exists from object type System.Data.Entity.Spatial.DbGeography to a known managed provider native type.

public class Position{...
public DbGeography Coordinates { get; set; }
...

position.Coordinates = DbGeography.FromText(string.Format("POINT({0} {1})", _longitude, _latitude));
...
cmd.CommandText = @"UPDATE Positions SET [Coordinates] = @Coordinates WHERE PositionId = 1";
cmd.Parameters.Add(new SqlParameter("@Coordinates", store.Coordinates));