自定义EXCEL导出格式

　　在项目中经常会用到这种情况：前台通过easyui自定义页表格展示，然后再通过excel导出到本地。

　　项目中用的最多的就是多级表头的情况，在这里markI一下。

　　1、自定义列对象

public class EasyUIDataColumn
{

public string field { get; set; }

private int _colspan = 1;
private int _rowspan = 1;


public string align = "left";
public int colspan
{
get { return _colspan; }
set { _colspan = value; }
}
public int rowspan
{
get { return _rowspan; }
set { _rowspan = value; }
}

public string title;
private int _width;

public int width
{
get
{
if (_width == 0)
{
if (DicEasyUIColumnWidth.ContainsKey(title)) { return DicEasyUIColumnWidth[title]; }
return 20 * _colspan * (Encoding.Default.GetBytes(title).Length / 2);
}
else
{
return _width;
}
}
set
{
_width = value;
}

}


public static readonly char EasyUIColumnSplit = '_';

}
}

　　2.通过从数据库中得到的DataTable数据生成对应的List<List<EasyUIDataColumn>>对象

   public List<List<EasyUIDataColumn>> GetEasyUIDataColumnList(string testID, DataTable dt, int frozenColumns = -1, bool isGetFrozenColumns = false)
        {
            List<List<EasyUIDataColumn>> arrEasyDataColumnList = new List<List<EasyUIDataColumn>>();
            List<EasyUIDataColumn> EasyDataColumnList = new List<EasyUIDataColumn>();
            List<EasyUIDataColumn> TitleColumnList = new List<EasyUIDataColumn>();
            for (int i = 0; i < dt.Columns.Count; i++)
            {
                EasyUIDataColumn easyDataColumn = new EasyUIDataColumn();
                easyDataColumn.width = 100;
                if (isGetFrozenColumns)
                {
                    if (i <= frozenColumns)
                    {
                        EasyUIDataColumn titleColumn = new EasyUIDataColumn();
                        titleColumn.rowspan = 2;
                        titleColumn.title = dt.Columns[i].ColumnName;
                        titleColumn.field = dt.Columns[i].ColumnName;
                        TitleColumnList.Add(titleColumn);
                        continue;
                    }
                }
                else
                {
                    if (i <= frozenColumns)
                    {
                        continue;
                    }
                }

                if (i == 2||i==6)
                {
                    EasyUIDataColumn titleColumn = new EasyUIDataColumn();
                    string[] columnName = dt.Columns[i].ColumnName.Split(EasyUIDataColumn.EasyUIColumnSplit);
                    titleColumn.colspan = 4;
                    titleColumn.title = columnName[0];
                    titleColumn.field = "";
                    TitleColumnList.Add(titleColumn);
                }


                if (dt.Columns[i].ColumnName.IndexOf(EasyUIDataColumn.EasyUIColumnSplit) > -1)
                {
                    string[] columnName = dt.Columns[i].ColumnName.Split(EasyUIDataColumn.EasyUIColumnSplit);
                    easyDataColumn.title = columnName[1];
                    easyDataColumn.field = dt.Columns[i].ColumnName;
                    easyDataColumn.align = "center";
                }
                else
                {
                    easyDataColumn.title = dt.Columns[i].ColumnName;
                    easyDataColumn.field = dt.Columns[i].ColumnName;
                    easyDataColumn.align = "center";
                }
                EasyDataColumnList.Add(easyDataColumn);
            }
            arrEasyDataColumnList.Add(TitleColumnList);
            arrEasyDataColumnList.Add(EasyDataColumnList);
            return arrEasyDataColumnList;
        }

　　3.根据自定义的表格式生成excel

　　

/// <summary>
        ///     将DataTable数据导出到Excel文件中(xlsx),自定义列头
        /// </summary>
        /// <param name="dt"></param>
        /// <param name="file"></param>
        /// <param name="columnList">列集合</param>
        /// <param name="frozenClounms">冻结列 或者 列表开始rowspan=2的列数 </param>
        public void ExportDataTableToExcelForXLSXByCustomColumn(DataTable dt, string file,
            List<List<EasyUIDataColumn>> columnList, int frozenClounms)
        {
            var xssfworkbook = new XSSFWorkbook();
            ICellStyle styleColName = xssfworkbook.CreateCellStyle();
            styleColName.Alignment = HorizontalAlignment.Center;
            styleColName.VerticalAlignment = VerticalAlignment.Center;
            var sheet = xssfworkbook.CreateSheet(dt.TableName); //sheet名
            var firstrow = 0;
            var lastrow = 0;
            var firstcol = 0;
            var lastcol = 0;
            //表头   
            for (var i = 0; i < columnList.Count; i++)
            {
                var sumColSpan = 0;

                for (var j = 0; j < columnList[i].Count; j++)
                {
                    int tempRowSpan = columnList[i][j].rowspan == 0 ? 1 : columnList[i][j].rowspan;
                    firstrow = i;
                    lastrow = i + tempRowSpan - 1;

                    int tempColSpan = columnList[i][j].colspan == 0 ? 1 : columnList[i][j].colspan;
                    firstcol = j + sumColSpan;
                    lastcol = j + sumColSpan + tempColSpan - 1;
                    sumColSpan += (tempColSpan - 1);

                    MergeColumn(sheet, firstrow, lastrow, firstcol, lastcol, columnList[i][j].title, styleColName, frozenClounms);
                }
            }
        
            sheet.SetColumnWidth(0, 15 * 256);
            //写入数据   
            for (var i = 0; i < dt.Rows.Count; i++)
            {
                var row1 = sheet.CreateRow(i + 2);
                for (var j = 0; j < dt.Columns.Count; j++)
                {
                    var cell = row1.CreateCell(j);
                    if (IsNumeric(dt.Rows[i][j].ToString()))
                    {
                        cell.SetCellType(CellType.Numeric);
                        cell.SetCellValue(Convert.ToDouble(dt.Rows[i][j]));
                    }
                    else
                    {
                        cell.SetCellValue(dt.Rows[i][j].ToString());
                    }
                }
            }

            //转为字节数组   
            var stream = new MemoryStream();
            xssfworkbook.Write(stream);
            var buf = stream.ToArray();

            //保存为Excel文件   
            using (var fs = new FileStream(file, FileMode.Create, FileAccess.Write))
            {
                fs.Write(buf, 0, buf.Length);
                fs.Close();
            }
        }

   private void MergeColumn(ISheet sheet, int firstrow, int lastrow, int firstcol, int lastcol, string value, ICellStyle cellStyle, int frozenClounms)
        {
            //第二行，全部往前进frozenClounms个列
            if (firstrow == 1)
            {
                firstcol += frozenClounms;
                lastcol += frozenClounms;
            }
            for (var i = firstrow; i <= lastrow; i++)
            {
                for (var j = firstcol; j <= lastcol; j++)
                {
                    if (j == firstcol)
                    {

                        LoadCell(sheet, i, j, cellStyle).SetCellValue(value);
                    }
                    else
                    {
                        LoadCell(sheet, i, j).SetCellValue("");
                    }
                }
            }
            sheet.AddMergedRegion(new CellRangeAddress(firstrow, lastrow, firstcol, lastcol)); //合并单元格
        }
        private ICell LoadCell(ISheet sheet1, int rowIndex, int cellIndex, ICellStyle cellStyle = null)
        {
            var row = sheet1.GetRow(rowIndex) ?? sheet1.CreateRow(rowIndex);

            var cell = row.GetCell(cellIndex);
            if (cell == null)
            {
                cell = sheet1.GetRow(rowIndex).CreateCell(cellIndex);
            }
            cell.CellStyle = cellStyle;
            return cell;
        }