根据index获取列编号，如传入1，得到A

public string Getzm(int Index)
{
var dividend = Index;
string columnName = string.Empty;

while (dividend > 0)
{
var modulo = (dividend - 1) % 26;
columnName = Convert.ToChar(65 + modulo) + columnName;
dividend = (dividend - modulo) / 26;
}
return columnName;
}

合并单元格

ExcelWorksheet ws

ws.Cells[$"{startName}:{endName}"].Style.HorizontalAlignment = ExcelHorizontalAlignment.Center;
ws.Cells[$"{startName}:{endName}"].Style.VerticalAlignment = ExcelVerticalAlignment.Center;
ws.Cells[$"{startName}:{endName}"].Merge = true;

注意，必须用ws.Cells[$"A1:C1"]这种方式而不是ws.Cells[1,1,1,3]这种，会报错

设置单元格格式

var cell = ws.Cells[$"{startName}:{endName}"]

cell.Style.Numberformat.Format = "yyyy-m-d";