Excel.Application  myExcel=new Excel.Application();
  myExcel.Application.Workbooks.Add(true);
  myExcel.Visible=true;
  Excel.Worksheet worksheet=(Excel.Worksheet)myExcel.ActiveSheet;

 Excel.Range  rH = worksheet.get_Range("A1","A3");  
  rH.Merge(0);
  myExcel.Cells[1,1]="赋值";