title: Displaying a message after adding duplicate records in database
body: <p>I wrote program in C# winforms and SQL server and LINQ to SQL. I use user control instead of form. In my user control, I put 3 textbox, txtStartNumber, txtEndNumber, txtQuantity. user define value of textboxes, when clicked button, it will insert some records according to the value of txtQuantity. </p>
  
  <p>I want to when duplicate number is created, it won't add to database and display message.
  how do i do? I must write code in code behind or server side? i must set this in store procedure or trigger?</p>
  
  <pre><code> private void btnSave_Click(object sender, EventArgs e)
          {
              long  from = Convert.ToInt64(txt_barcode_f.Text);
              long to = Convert.ToInt64(txt_barcode_t.Text);
              long quantity = Convert.ToInt64(to - from);
              int card_Type_ID=Convert.ToInt32(cmb_BracodeType .SelectedValue);
              long[] arrCardNum = new long[(to - from)];
  
              arrCardNum[0]=from;
  
              for (long i = from; i &lt; to; i++)
               {
                   for(int j=0; j&lt;(to-from) ;j++)
                   {
                   arrCardNum[j]=from+j;
                   string r = arrCardNum[j].ToString();
                   sp.SaveCards(r, 2, card_Type_ID, SaveDate, 2);
                   }
               }
          }
  </code></pre>
  
  <p>Stored Procedure code.</p>
  
  <pre><code>ALTER PROCEDURE dbo.SaveCards
  @Barcode_Num int
  ,@Card_Status_ID int 
  ,@Card_Type_ID int
  ,@SaveDate varchar(10)
  ,@Save_User_ID int 
  
  
  AS
  
  BEGIN 
  INSERT INTO [Parking].[dbo].[TBL_Cards]
             ([Barcode_Num]
             ,[Card_Status_ID]
             ,[Card_Type_ID]       
             ,[Save_User_ID])
  
       VALUES
             (@Barcode_Num
             ,@Card_Status_ID
             ,@Card_Type_ID
             ,@Save_User_ID)
  
  
      END  
  </code></pre>