Microsoft.Office.Interop.Excel.Application excapp;
excapp = new Microsoft.Office.Interop.Excel.Application();
object misval=System.Reflection.Missing.Value;
Workbook wrkbuk = new Workbook();
Worksheet wrksht = new Worksheet();
wrkbuk = excapp.Workbooks._Open(@"C:\Users\...\..._template_v1.0.xlsx", misval, misval,
misval, misval, misval, misval, misval, misval, misval, misval, misval, misval);
wrksht = (Microsoft.Office.Interop.Excel.Worksheet)wrkbuk.Worksheets.get_Item(2);