导出到excel类

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Text;
using System.Globalization;
using System.IO;
namespace CSPlatform.Website.Admin
{
    public class ExcelHelper
    {

        #region Fields

        string _fileName;
        DataTable _dataSource;
        string[] _titles = null;
        string[] _fields = null;
        int _maxRecords = 1000;

        #endregion

        #region Properties

        /**/
        /// <summary>
        /// 限制输出到 Excel 的最大记录数。超出则抛出异常
        /// </summary>
        public int MaxRecords
        {
            set { _maxRecords = value; }
            get { return _maxRecords; }
        }

        /**/
        /// <summary>
        /// 输出到浏览器的 Excel 文件名
        /// </summary>
        public string FileName
        {
            set { _fileName = value; }
            get { return _fileName; }
        }

        #endregion

        #region .ctor

        /**/
        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="titles">要输出到 Excel 的列标题的数组</param>
        /// <param name="fields">要输出到 Excel 的字段名称数组</param>
        /// <param name="dataSource">数据源</param>
        public ExcelHelper(string[] titles, string[] fields, DataTable dataSource)
            : this(titles, dataSource)
        {
            if (fields == null || fields.Length == 0)
                throw new ArgumentNullException("fields");

            if (titles.Length != fields.Length)
                throw new ArgumentException("titles.Length != fields.Length", "fields");

            _fields = fields;
        }

        /**/
        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="titles">要输出到 Excel 的列标题的数组</param>
        /// <param name="dataSource">数据源</param>
        public ExcelHelper(string[] titles, DataTable dataSource)
            : this(dataSource)
        {
            if (titles == null || titles.Length == 0)
                throw new ArgumentNullException("titles");
            //if (titles.Length != dataSource.Columns.Count)
            //    throw new ArgumentException("titles.Length != dataSource.Columns.Count", "dataSource");

            _titles = titles;
        }

        /**/
        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="dataSource">数据源</param>
        public ExcelHelper(DataTable dataSource)
        {
            if (dataSource == null)
                throw new ArgumentNullException("dataSource");
            // maybe more checks needed here (IEnumerable, IList, IListSource, ) ???
            // 很难判断，先简单的使用 DataTable

            _dataSource = dataSource;
        }

        public ExcelHelper() { }

        #endregion

        #region public Methods

        /**/
        /// <summary>
        /// 导出到 Excel 并提示下载
        /// </summary>
        /// <param name="dg">DataGrid</param>
        public void Export(DataGrid dg)
        {
            if (dg == null)
                throw new ArgumentNullException("dg");
            if (dg.AllowPaging || dg.PageCount > 1)
                throw new ArgumentException("paged DataGrid can't be exported.", "dg");

            // 添加标题样式
            dg.HeaderStyle.Font.Bold = true;
            dg.HeaderStyle.BackColor = System.Drawing.Color.LightGray;

            RenderExcel(dg);
        }

 

        /**/
        /// <summary>
        /// 导出到 Excel 并提示下载
        /// </summary>
        public void Export()
        {
            if (_dataSource == null)
                throw new Exception("数据源尚未初始化");

            if (_fields == null && _titles != null && _titles.Length != _dataSource.Columns.Count)
                throw new Exception("_titles.Length != _dataSource.Columns.Count");

            if (_dataSource.Rows.Count > _maxRecords)
                throw new Exception("导出数据条数超过限制。请设置 MaxRecords 属性以定义导出的最多记录数。");

            DataGrid dg = new DataGrid();
            dg.DataSource = _dataSource;

            if (_titles == null)
            {
                dg.AutoGenerateColumns = true;
            }
            else
            {
                dg.AutoGenerateColumns = false;
                int cnt = _titles.Length;

                System.Web.UI.WebControls.BoundColumn col;

                if (_fields == null)
                {
                    for (int i = 0; i < cnt; i++)
                    {
                        col = new System.Web.UI.WebControls.BoundColumn();
                        col.HeaderText = _titles[i];
                        col.DataField = _dataSource.Columns[i].ColumnName;
                        dg.Columns.Add(col);
                    }
                }
                else
                {
                    for (int i = 0; i < cnt; i++)
                    {
                        col = new System.Web.UI.WebControls.BoundColumn();
                        col.HeaderText = _titles[i];
                        col.DataField = _fields[i];
                        dg.Columns.Add(col);
                    }
                }
            }

            // 添加标题样式
            dg.HeaderStyle.Font.Bold = true;
            dg.HeaderStyle.BackColor = System.Drawing.Color.LightGray;
            dg.ItemDataBound += new DataGridItemEventHandler(DataGridItemDataBound);

            dg.DataBind();
            RenderExcel(dg);
        }

        #endregion

 

        #region private Methods

        private void RenderExcel(Control c)
        {
            // 确保有一个合法的输出文件名
            if (_fileName == null || _fileName == string.Empty || !(_fileName.ToLower().EndsWith(".xls")))
                _fileName = GetRandomFileName();

            HttpResponse response = HttpContext.Current.Response;

            response.Charset = "GB2312";
            response.ContentEncoding = Encoding.GetEncoding("GB2312");
            response.ContentType = "application/ms-excel/msword";
            response.AppendHeader("Content-Disposition", "attachment;filename=" +
                HttpUtility.UrlEncode(_fileName));

            CultureInfo cult = new CultureInfo("zh-CN", true);
            StringWriter sw = new StringWriter(cult);
            HtmlTextWriter writer = new HtmlTextWriter(sw);

            writer.WriteLine("<meta http-equiv=\"Content-Type\" content=\"text/html;charset=GB2312\">");

            DataGrid dg = c as DataGrid;

            if (dg != null)
            {
                dg.RenderControl(writer);
            }

            c.Dispose();

            response.Write(sw.ToString());
            response.End();
        }

        /**/
        /// <summary>
        /// 得到一个随意的文件名
        /// </summary>
        /// <returns></returns>
        private string GetRandomFileName()
        {
            Random rnd = new Random((int)(DateTime.Now.Ticks));
            string s = rnd.Next(Int32.MaxValue).ToString();
            return DateTime.Now.ToShortDateString() + "_" + s + ".xls";
        }

        private void DataGridItemDataBound(object sender, System.Web.UI.WebControls.DataGridItemEventArgs e)
        {
            if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
            {
                e.Item.Attributes.Add("style", "vnd.ms-excel.numberformat:@");
                //e.Item.Cells[3].Attributes.Add("style", "vnd.ms-excel.numberformat:￥#,###.00");
            }
        }

        #endregion

    }
}