C# 使用EPPlus 操作excel The given key '8' was not present in the dictionary.

使用EPPlus 删除excel中某一个sheet中的几列的时候，出现了The given key '8' was not present in the dictionary.的报错；

最开始的写法，是从前往后删除，出现错误
//ExcelWorksheet sheet = package.Workbook.Worksheets[i];
//sheet.DeleteColumn(4);//单价（未税）
//sheet.DeleteColumn(4);//单价（含税）
//sheet.DeleteColumn(8);//未税总额
//sheet.DeleteColumn(16);//目标价格
//sheet.DeleteColumn(16);//应该成本小计
//sheet.DeleteColumn(16);//目标成本小计
//sheet.DeleteColumn(16);//差额

改成从后往前删除，问题就解决了

ExcelWorksheet sheet = package.Workbook.Worksheets[i];
sheet.DeleteColumn(22);//差额
sheet.DeleteColumn(21);//目标成本小计
sheet.DeleteColumn(20);//应该成本小计
sheet.DeleteColumn(19);//目标价格
sheet.DeleteColumn(10);//未税总额
sheet.DeleteColumn(5);//单价（含税）
sheet.DeleteColumn(4);//单价（未税）