C# ต้องการ ตรวจสอบ ค่าซ้ำก่อน insert ข้อมูล ลงดาต้าเบสครับ

public static System.Data.DataTable GetTableForm(string _SQL, string strConn)
        {
            System.Data.DataSet ds = new System.Data.DataSet();
                    System.Data.SqlClient.SqlConnection conn3 = new System.Data.SqlClient.SqlConnection(strConn);
                    conn3.Open();
                    System.Data.SqlClient.SqlDataAdapter adapter3 = new System.Data.SqlClient.SqlDataAdapter(_SQL, conn3);
                    adapter3.Fill(ds);
            return ds.Tables[0];

        }
        private void SaveDatabase()
        {
            string SQL = "";
            //เช็คก่อนว่ามีข้อมูลนี้หรือไม่
            if (GetTableForm("select * from table where ID = " + "11", "ConnString").Rows.Count > 0)
            {
                SQL = "Update .... Where ID = " + "11"; //ถ้ามี SQL จะเป็น Update
            }
            else
            {
                SQL = "Insert into ...."; //ถ้าไม่มี SQL จะเป็น Insert
            }
            //เอา SQL ไปใช้งาน
            System.Data.DataTable dt = GetTableForm(SQL, "ConnString"); 
            //Save นี้จะได้ทั้ง Update/Insert 
        }

			int intNumRows;
			strSQL = "SELECT COUNT(*) FROM customer WHERE CustomerID = '"+ this.txtCustomerID.Text +"' ";
			objCmd = new MySqlCommand(strSQL, objConn);
			intNumRows = Convert.ToInt32(objCmd.ExecuteScalar());

			if(intNumRows > 0)
			{
				this.pnlAdd.Visible = false;
				this.lblStatus.Visible = true;
				this.lblStatus.Text = "CustomerID already exists.";
			}
			else
			{
				strSQL = "INSERT INTO customer (CustomerID,Name,Email,CountryCode,Budget,Used) " +
				" VALUES " +
				" ('" + this.txtCustomerID.Text + "','" + this.txtName.Text + "','" + this.txtEmail.Text + "', " +
				" '" + this.txtCountryCode.Text + "','" + this.txtBudget.Text + "','" + this.txtUsed.Text + "')";

				objCmd = new MySqlCommand();
				objCmd.Connection = objConn;
				objCmd.CommandText = strSQL;
				objCmd.CommandType = CommandType.Text;
								
				this.pnlAdd.Visible = false;

				try
				{
					objCmd.ExecuteNonQuery();
					this.lblStatus.Text = "Record Inserted";
					this.lblStatus.Visible = true;
				}
				catch (Exception ex)
				{
					this.lblStatus.Visible = true;
					this.lblStatus.Text = "Record can not insert Error ("+ ex.Message +")";
				}
		}