Dynamically Create Variables in Script Task of SSIS

How to Dynamically Create Variables in Script Task. Urgent Please!!

I am using 

Dts.Variables.Add("myVar1", true, "User", 5); 

method but its giving error like this:

Exception from HRESULT: 0xC0016026 ---> System.Runtime.InteropServices.COMException (0xC0016026): Exception from HRESULT: 0xC0016026
   at Microsoft.SqlServer.Dts.Runtime.Wrapper.IDTSVariables100.Add(String bstrName, Boolean bReadOnly, String bstrNamespace, Object vValue)
   at Microsoft.SqlServer.Dts.Runtime.Variables.Add(String name, Boolean readOnly, String nameSpace, Object val)
   --- End of inner exception stack trace ---
   at Microsoft.SqlServer.Dts.Runtime.Variables.Add(String name, Boolean readOnly, String nameSpace, Object val)
   at ST_3de12d4b97354b57bf8c88a45589084f.csproj.ScriptMain.Main()
   --- End of inner exception stack trace ---

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avm