using System;
using System.Collections.Generic;
using System.Text;

using System.Xml;
using System.Xml.Xsl;
using System.Web;
using System.Data;
using System.IO;

namespace Web.Common
{
    public class ExcelDownLoad
    {/// <summary>
        /// 的数据源的数据
        /// </summary>
        /// <param name="dt">数据源</param>
        /// <param name="fileName">输出文件名</param>
        public static void Export(DataTable dt, string fileName)
        {
            DataSet dsExport = new DataSet("Export");
            DataTable dtExport = dt.Copy();

dtExport.TableName = "Values";
            dsExport.Tables.Add(dtExport);

string[] headers = new string[dtExport.Columns.Count];
            string[] fields = new string[dtExport.Columns.Count];

for (int i = 0; i < dtExport.Columns.Count; i++)
            {
                headers[i] = String.IsNullOrEmpty(dtExport.Columns[i].Caption) ? dtExport.Columns[i].ColumnName : dtExport.Columns[i].Caption;
                fields[i] = ReplaceSpecialChars(dtExport.Columns[i].ColumnName);
            }

Export(dsExport, headers, fields, fileName, Encoding.GetEncoding("GB2312"));
        }

/// <summary>
        /// 导出的数据源的数据
        /// </summary>
        /// <param name="ds">数据源</param>
        /// <param name="fields">导出的字段数组</param>
        /// <param name="fileName">输出文件名</param>
        /// <param name="encoding">编码</param>
        private static void Export(DataSet ds, string[] headers, string[] fields, string fileName, Encoding encoding)
        {
            HttpContext.Current.Response.Clear();
            HttpContext.Current.Response.Buffer = true;
            HttpContext.Current.Response.ContentType = "text/csv";
            HttpContext.Current.Response.AddHeader("content-disposition", String.Format("attachment;filename={0}.{1}", HttpUtility.UrlEncode(fileName, System.Text.Encoding.UTF8), "csv").Replace("+", "%20"));
            HttpContext.Current.Response.ContentEncoding = encoding;

MemoryStream stream = new MemoryStream();
            XmlTextWriter writer = new XmlTextWriter(stream, encoding);

CreateStylesheet(writer, headers, fields);
            writer.Flush();
            stream.Seek(0, SeekOrigin.Begin);

XmlDataDocument xmlDoc = new XmlDataDocument(ds);
            XslCompiledTransform xslTran = new XslCompiledTransform();
            xslTran.Load(new XmlTextReader(stream));

System.IO.StringWriter sw = new System.IO.StringWriter();
            xslTran.Transform(xmlDoc, null, sw);

HttpContext.Current.Response.Write(sw.ToString());
            sw.Close();
            writer.Close();
            stream.Close();
            HttpContext.Current.Response.End();
        }

/// <summary>
        /// 动态生成XSL，并写入XML流
        /// </summary>
        /// <param name="writer">XML流</param>
        /// <param name="headers">表头数组</param>
        /// <param name="fields">字段数组</param>
        /// <param name="exportFormat">导出文件的格式</param>
        private static void CreateStylesheet(XmlTextWriter writer, string[] headers, string[] fields)
        {
            string ns = "http://www.w3.org/1999/XSL/Transform";
            writer.Formatting = Formatting.Indented;
            writer.WriteStartDocument();
            writer.WriteStartElement("xsl", "stylesheet", ns);
            writer.WriteAttributeString("version", "1.0");

writer.WriteStartElement("xsl:output");
            writer.WriteAttributeString("method", "text");
            writer.WriteAttributeString("version", "4.0");
            writer.WriteEndElement();

// xsl-template
            writer.WriteStartElement("xsl:template");
            writer.WriteAttributeString("match", "/");

// xsl:value-of for headers
            for (int i = 0; i < headers.Length; i++)
            {
                writer.WriteString("\"");
                writer.WriteStartElement("xsl:value-of");
                writer.WriteAttributeString("select", "'" + headers[i] + "'");
                writer.WriteEndElement(); // xsl:value-of
                writer.WriteString("\"");
                if (i != fields.Length - 1) writer.WriteString(",");
            }

// xsl:for-each
            writer.WriteStartElement("xsl:for-each");
            writer.WriteAttributeString("select", "Export/Values");
            writer.WriteString("\r\n");

// xsl:value-of for data fields
            for (int i = 0; i < fields.Length; i++)
            {
                writer.WriteString("\"");
                writer.WriteStartElement("xsl:value-of");
                writer.WriteAttributeString("select", fields[i]);
                writer.WriteEndElement(); // xsl:value-of
                writer.WriteString("\"");
                if (i != fields.Length - 1) writer.WriteString(",");
            }

writer.WriteEndElement(); // xsl:for-each
            writer.WriteEndElement(); // xsl-template
            writer.WriteEndElement(); // xsl:stylesheet
        }

/// <summary>
        ///  替换特殊字符
        /// </summary>
        /// <param name="input">字符串</param>
        /// <returns></returns>
        public static string ReplaceSpecialChars(string input)
        {
            // space     ->     _x0020_
            // %        ->     _x0025_
            // #        ->    _x0023_
            // &        ->    _x0026_
            // /        ->    _x002F_
            if (!String.IsNullOrEmpty(input))
            {
                input = input.Replace(" ", "_x0020_")
            .Replace("%", "_x0025_")
            .Replace("#", "_x0023_")
            .Replace("&", "_x0026_")
            .Replace("/", "_x002F_");
            }

return input;
        }
    }
}