C# คำสั่งเช็คข้อมูลในฐานข้อมูลด้วยwcfแล้วแจ้งเออเร่อกลับมาที่winfrom

public bool SaveCustomers2(Customers cust)
{
using (var entity = new NorthwindEntities())
            {
                List<Customers> cust = (from c in entity.Customers where c.CustomerID.equal(cust.CustomerID) and c.CustomerName.equal(cust.CustomerName) and c.CustomerPhone.equal(cust.CustomerPhone) select c).ToList();
if (cust.Count ==0 )
               if (cust.Count ==0 )
               {                                  
                try
                {
                     entity.AddToCustomers(cust);
                     entity.SaveChanges();   
                }
                catch (Exception SaveEx)
                {
                     throw new System.Exception(ex.ToString());
                     return false;
                } 
               }
               else
             {
                  throw new System.Exception("duplicate:" +cust.Count.ToString());
                  return false;
             }                           
             }
             return true;

}

private void button4_Click(object sender, EventArgs e)
        {
            PetStoreServics.Customer oCustomer = new PetStoreWinForm.PetStoreServics.Customer();
            oCustomer.Name = textBox1.Text;
            oCustomer.LastName = textBox2.Text;
            oCustomer.RegisteredDate = dateTimePicker1.Value;
            PetStoreServics.Service1Client PetStoreServics = new PetStoreWinForm.PetStoreServics.Service1Client();
            {
                if (!PetStoreServics.SaveCustomers2(oCustomer.Name))
                {
                try
                {
                    if (oCustomer.Name == string.Empty)
                    {
                        MessageBox.Show(" กรุณากรอกข้อมูลด้วยค่ะ!!");
                    }

                    else 
                        MessageBox.Show("Save Data Complete");
                }
              catch (Exception)
                {

                    throw;
                }
            }
            else
            {
                MessageBox.Show("ชื่อนี้มีอยู่ในระบบแล้ว");
            }
            showdata();
        }  
            }
        }