NOPI创建Excel后中文单元格的列宽自适应

NPOI自带的列宽自适应方法只支持英文和数字，若要支持中文需要自己添加方法

//列宽自适应，只对英文和数字有效
for (int i = 0; i <= MaxColumn; i++)
{
sheet.AutoSizeColumn(i);
}

//列宽自适应，支持中文

    for (int columnNum = 0; columnNum <= MaxColumn; columnNum++)
            {
                int columnWidth = sheet.GetColumnWidth(columnNum) / 256;
                for (int rowNum = 1; rowNum <= sheet.LastRowNum; rowNum++)
                {
                    IRow currentRow;
                    //当前行未被使用过
                    if (sheet.GetRow(rowNum) == null)
                    {
                        currentRow = sheet.CreateRow(rowNum);
                    }
                    else
                    {
                        currentRow = sheet.GetRow(rowNum);
                    }
                    if (currentRow.GetCell(columnNum) != null)
                    {
                        ICell currentCell = currentRow.GetCell(columnNum);
                        int length = Encoding.Default.GetBytes(currentCell.ToString()).Length;
                        if (columnWidth < length)
                        {
                            columnWidth = length+3; //+3是为了美观
                        }
                    }
                }
                sheet.SetColumnWidth(columnNum, columnWidth * 256);
            }