Getting this error, not all code paths return a value

I want to get data from database.so I write a code in BussinessLogicLayer.cs class within that class I have get method & its raising the error "not all code paths return a value".For this my project does not build successfully.So what should i do..Plz do needful.
 
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
namespace BussinessLayer
{
    public class EmployeeBussinessLayer
    {
        public IEnumerable<Employee> Employees
        {
            get
            {
                string connectionString = ConfigurationManager.ConnectionStrings["DBCS"].ConnectionString;
                List<Employee> employees = new List<Employee>();
                using (SqlConnection con = new SqlConnection(connectionString))
                {
                    SqlCommand cmd = new SqlCommand("spGetAllEmployees", con);
                    cmd.CommandType = CommandType.StoredProcedure;
                    con.Open();
                    SqlDataReader rdr = cmd.ExecuteReader();
                    while (rdr.Read())
                    {
                        Employee employee = new Employee();
                        employee.ID = Convert.ToInt32(rdr["Id"]);
                        employee.Name = rdr["Name"].ToString();
                        employee.Gender = rdr["Gender"].ToString();
                        employee.City = rdr["City"].ToString();
                        employee.DateOfBirth = Convert.ToDateTime(rdr["DateOfBirth"]);
                        employees.Add(employee);
                    }
                }
            }
        }
    }
}