Integration Services :: Excel Reading In SSIS Script Task

I used the below code to read excel files  in SSIS 2008R2 script component and it is working fine but when i copied it in Script Task of SSIS 2012, the code doesnt work. I have define one variable

Var_ExcelFileName and stored location of excel file.

/* Microsoft SQL Server Integration Services Script Component
* Write scripts using Microsoft Visual C# 2008.
* ScriptMain is the entry point class of the script.*/

using System;
using System.Data;
using Microsoft.SqlServer.Dts.Pipeline.Wrapper;
using Microsoft.SqlServer.Dts.Runtime.Wrapper;

[Code] ....

 I am getting errors in the below lines:

using Microsoft.SqlServer.Dts.Pipeline.Wrapper;
using Microsoft.SqlServer.Dts.Runtime.Wrapper;

And Also in this line:

dt = LoadWorkbook(Variables.VarExcelFileName,
"Sheet1");