System.InvalidOperationException: ‘ExecuteReader: Connection property has not been initialized.’

علت خطای زیر چیست؟

SqlConnection _con = new  SqlConnection (“Data Source = .; Initial Catalog = Shop3; Integrated Security = true;”);
_con.Open();
SqlCommand  cmd = new  SqlCommand (” select * from Customer “);
SqlDataReader  reader = cmd.ExecuteReader();
while ( reader.Read() )
{
Console.WriteLine(“Customer Code: {0}nCustomer Name {1}nCustomer Family: {2}nCustomer Phone: {3}”,
reader.GetInt32(0), reader.GetString(1), reader.GetString(2), reader.GetString(3));
}
_con.Close();