0. 導入命名空間：

using Microsoft.Office.Core;

0.合並豎著的單元格

Range rangeLecture = worksheet.get_Range(worksheet.Cells[1, 1], worksheet.Cells[2,  1]);
                    rangeLecture.Application.DisplayAlerts = false;
                    rangeLecture.Merge(Missing.Value);
                    rangeLecture.Application.DisplayAlerts = true;

1.合並橫著的單元格
 

Range rangeProgram = worksheet.get_Range(worksheet.Cells[1, 1], worksheet.Cells[1, 2]);
                     rangeProgram.Application.DisplayAlerts = false;  
                     rangeProgram.Merge(Missing.Value); 
                     rangeProgram.Application.DisplayAlerts = true;

C# 操作Excel 整理