C# NPOI 合并区域后添加border

 默认的excel边框样式对于合并后的excel无效需要使用RegionUtil设置边框样式，具体如下：

CellRangeAddress四个参数分别代表对应的 起始行号，终结行号，起始列号，终结列号；

new CellRangeAddress(0, 0, 0, 0);

public static void setRegionBorderStyle(int border, CellRangeAddress region, IRow row)
{
    RegionUtil.SetBorderBottom(border, region, row.Sheet);
    RegionUtil.SetBorderLeft(border, region, row.Sheet);
    RegionUtil.SetBorderRight(border, region, row.Sheet);
    RegionUtil.SetBorderTop(border, region, row.Sheet);
    row.Sheet.AddMergedRegion(region);
}