To get unique values from xls Colomn

Consider using the DDT.ExcelDriver object. This allows you to connect to your Excel sheet and then interate through the records to find what you're looking for.  You can also pass in an SQL query to this object to reduce the recordset down to only what you want by calling the ADOCommandObject.CommandText. Something like this

var MyExcelRecords;

MyExcelRecords = DDT.ExcelDriver("C:\MyDir\MyExcel.xls");
MyExcelRecords.ADOCommandObject.CommandText = "SELECT DISTINCT Col_1 from MyExcel.xls";