validation

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C#

ASP.NET

i am inserting bulk data from excel to sql database. i am using SqlBulkCopy for insertion. but i want to do validation. for example if there s no data in one of the cell of cell means it should check and error message should display. help. am in urgency. i tried using while loop. but not working.
This my code:

while (dReader.Read())
       {
           SqlBulkCopy sb = new SqlBulkCopy(con);


           sb.DestinationTableName = "sampletable";

           sb.ColumnMappings.Add("adate", "adate");
           if (dReader[1].ToString() == "")
           {
               Label1.Text = "check";

           }
           else
           {
               sb.ColumnMappings.Add("ex_id", "ex_id");
           }
           sb.ColumnMappings.Add("empid", "empid");
           sb.ColumnMappings.Add("name", "name");
           sb.ColumnMappings.Add("sal", "sal");

           con.Open();

           sb.WriteToServer(dReader);
       }