1:
2:
3:
4:
5:
6:
7:
8:
9:

Excel.Application app = new Excel.Application();
Workbooks wb = app.Workbooks;
app.Visible = false;
Workbook _wb = wb.Add(XlWBATemplate.xlWBATWorksheet);
Sheets sheets = _wb.Worksheets;
Worksheet _ws = (Worksheet)sheets.get_Item(i);
Range r1 = _ws.Rows;
Range r2 = (Range)r1.Cells.get_Item(1, 1);
r2.Value2 = "test";                    

1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:

Assembly externeAssembly = Assembly.LoadFrom("Interop.Excel.dll");
Type excelApplicationType = externeAssembly.GetType("Excel.ApplicationClass");
object excelApplication = Activator.CreateInstance(excelApplicationType);
            
excelApplicationType.InvokeMember("Visible", BindingFlags.SetProperty, null, excelApplication, new object[] { false });
object excelWorkbooks = excelApplicationType.InvokeMember("Workbooks", BindingFlags.GetProperty, null, excelApplication, null);
Type excelWorkbooksType = externeAssembly.GetType("Excel.Workbooks");
object excelWorkbook = excelWorkbooksType.InvokeMember("Add", BindingFlags.InvokeMethod, null, excelWorkbooks, new object[] { XlWBATemplate.xlWBATWorksheet });
Type excelWorkbookType = externeAssembly.GetType("Excel.Workbook");

object excelSheets = excelWorkbookType.InvokeMember("Worksheets", BindingFlags.GetProperty, null, excelWorkbook, null);
Type excelSheetsType = externeAssembly.GetType("Excel.Sheets");

object excelWorkSheet = excelSheetsType.InvokeMember("get_Item", BindingFlags.InvokeMethod, null, excelSheets, new object[] { 1 });