/// <summary>
/// 将datatable中的数据导出到指定的excel文件中
/// </summary>
/// <param name="page">web页面对象</param>
/// <param name="tab">包含被导出数据的datatable对象</param>
/// <param name="filename">excel文件的名称</param>
public static void export(system.web.ui.page page,system.data.datatable tab,string filename)
{
system.web.httpresponse httpresponse = page.response;
system.web.ui.webcontrols.datagrid datagrid=new system.web.ui.webcontrols.datagrid();
datagrid.datasource=tab.defaultview;
datagrid.allowpaging = false;
datagrid.headerstyle.backcolor = system.drawing.color.green;
datagrid.headerstyle.horizontalalign = horizontalalign.center;
datagrid.headerstyle.font.bold = true;
datagrid.databind();
httpresponse.appendheader("content-disposition","attachment;filename="+httputility.urlencode(filename,system.text.encoding.utf8)); //filename="*.xls";
httpresponse.contentencoding=system.text.encoding.getencoding("gb2312");
httpresponse.contenttype ="application/ms-excel";
system.io.stringwriter tw = new system.io.stringwriter() ;
system.web.ui.htmltextwriter hw = new system.web.ui.htmltextwriter (tw);
datagrid.rendercontrol(hw);

string filepath = page.server.mappath("..")+"\\files\\" +filename;
system.io.streamwriter sw = system.io.file.createtext(filepath);
sw.write(tw.tostring());
sw.close();

downfile(httpresponse,filename,filepath);

httpresponse.end();
}
private static bool downfile(system.web.httpresponse response,string filename,string fullpath)
{
try
{
response.contenttype = "application/octet-stream";

response.appendheader("content-disposition","attachment;filename=" +
httputility.urlencode(filename,system.text.encoding.utf8) + ";charset=gb2312");
system.io.filestream fs= system.io.file.openread(fullpath);
long flen=fs.length;
int size=102400;//每100k同时下载数据
byte[] readdata = new byte[size];//指定缓冲区的大小
if(size>flen)size=convert.toint32(flen);
long fpos=0;
bool isend=false;
while (!isend)
{
if((fpos+size)>flen)
{
size=convert.toint32(flen-fpos);
readdata = new byte[size];
isend=true;
}
fs.read(readdata, 0, size);//读入一个压缩块
response.binarywrite(readdata);
fpos+=size;
}
fs.close();
system.io.file.delete(fullpath);
return true;
}
catch
{
return false;
}
}

/// <summary>
/// 将指定excel文件中的数据转换成datatable对象，供应用程序进一步处理
/// </summary>
/// <param name="filepath"></param>
/// <returns></returns>
public static system.data.datatable import(string filepath)
{
system.data.datatable rs = new system.data.datatable();
bool canopen=false;

oledbconnection conn = new oledbconnection("provider=microsoft.jet.oledb.4.0;"+
"data source=" + filepath + ";" +
"extended properties=\"excel 8.0;\"");

try//尝试数据连接是否可用
{
conn.open();
conn.close();
canopen=true;
}
catch{}

if(canopen)
{
try//如果数据连接可以打开则尝试读入数据
{
oledbcommand myoledbcommand = new oledbcommand("select * from [sheet1$]",conn);
oledbdataadapter mydata = new oledbdataadapter(myoledbcommand);
mydata.fill(rs);
conn.close();
}
catch//如果数据连接可以打开但是读入数据失败，则从文件中提取出工作表的名称，再读入数据
{
string sheetname=getsheetname(filepath);
if(sheetname.length>0)
{
oledbcommand myoledbcommand = new oledbcommand("select * from ["+sheetname+"$]",conn);
oledbdataadapter mydata = new oledbdataadapter(myoledbcommand);
mydata.fill(rs);
conn.close();
}
}
}
else
{
system.io.streamreader tmpstream=file.opentext(filepath);
string tmpstr=tmpstream.readtoend();
tmpstream.close();
rs=getdatatablefromstring(tmpstr);
tmpstr="";
}
return rs;
}
/// <summary>
/// 将指定html字符串的数据转换成datatable对象 --根据“<tr><td>”等特殊字符进行处理
/// </summary>
/// <param name="tmphtml">html字符串</param>
/// <returns></returns>
private static datatable getdatatablefromstring(string tmphtml)
{
string tmpstr=tmphtml;
datatable tb=new datatable();
//先处理一下这个字符串，删除第一个<tr>之前合最后一个</tr>之后的部分
int index=tmpstr.indexof("<tr");
if(index>-1)
tmpstr=tmpstr.substring(index);
else
return tb;

index=tmpstr.lastindexof("</tr>");
if(index>-1)
tmpstr=tmpstr.substring(0,index+5);
else
return tb;

bool existssparator=false;
char separator=convert.tochar("^");

//如果原字符串中包含分隔符“^”则先把它替换掉
if(tmpstr.indexof(separator.tostring())>-1)
{
existssparator=true;
tmpstr=tmpstr.replace("^","^$&^");
}

//先根据“</tr>”分拆
string[] tmprow=tmpstr.replace("</tr>","^").split(separator);

for(int i=0;i<tmprow.length-1;i++)
{
datarow newrow=tb.newrow();

string tmpstri=tmprow[i];
if(tmpstri.indexof("<tr")>-1)
{
tmpstri=tmpstri.substring(tmpstri.indexof("<tr"));
if(tmpstri.indexof("display:none")<0||tmpstri.indexof("display:none")>tmpstri.indexof(">"))
{
tmpstri=tmpstri.replace("</td>","^");
string[] tmpfield=tmpstri.split(separator);

for(int j=0;j<tmpfield.length-1;j++)
{
tmpfield[j]=removestring(tmpfield[j],"<font>");
index=tmpfield[j].lastindexof(">")+1;
if(index>0)
{
string field=tmpfield[j].substring(index,tmpfield[j].length-index);
if(existssparator) field=field.replace("^$&^","^");
if(i==0)
{
string tmpfieldname=field;
int sn=1;
while(tb.columns.contains(tmpfieldname))
{
tmpfieldname=field+sn.tostring();
sn+=1;
}
tb.columns.add(tmpfieldname);
}
else
{
newrow[j]=field;
}
}//end of if(index>0)
}

if(i>0)
tb.rows.add(newrow);
}
}
}

tb.acceptchanges();
return tb;
}

/// <summary>
/// 从指定html字符串中剔除指定的对象
/// </summary>
/// <param name="tmphtml">html字符串</param>
/// <param name="remove">需要剔除的对象--例如输入"<font>"则剔除"<font ???????>"和"</font>>"</param>
/// <returns></returns>
public static string removestring(string tmphtml,string remove)
{
tmphtml=tmphtml.replace(remove.replace("<","</"),"");
tmphtml=removestringhead(tmphtml,remove);
return tmphtml;
}
/// <summary>
/// 只供方法removestring()使用
/// </summary>
/// <returns></returns>
private static string removestringhead(string tmphtml,string remove)
{
//为了方便注释，假设输入参数remove="<font>"
if(remove.length<1) return tmphtml;//参数remove为空：不处理返回
if((remove.substring(0,1)!="<")||(remove.substring(remove.length-1)!=">")) return tmphtml;//参数remove不是<?????>：不处理返回

int indexs=tmphtml.indexof(remove.replace(">",""));//查找“<font”的位置
int indexe=-1;
if(indexs>-1)
{
string tmpright=tmphtml.substring(indexs,tmphtml.length-indexs);
indexe=tmpright.indexof(">");
if(indexe>-1)
tmphtml=tmphtml.substring(0,indexs)+tmphtml.substring(indexs+indexe+1);
if(tmphtml.indexof(remove.replace(">",""))>-1)
tmphtml=removestringhead(tmphtml,remove);
}
return tmphtml;
}

/// <summary>
/// 将指定excel文件中读取第一张工作表的名称
/// </summary>
/// <param name="filepath"></param>
/// <returns></returns>
private static string getsheetname(string filepath)
{
string sheetname="";

system.io.filestream tmpstream=file.openread(filepath);
byte[] filebyte=new byte[tmpstream.length];
tmpstream.read(filebyte,0,filebyte.length);
tmpstream.close();

byte[] tmpbyte=new byte[]{convert.tobyte(11),convert.tobyte(0),convert.tobyte(0),convert.tobyte(0),convert.tobyte(0),convert.tobyte(0),convert.tobyte(0),convert.tobyte(0),
convert.tobyte(11),convert.tobyte(0),convert.tobyte(0),convert.tobyte(0),convert.tobyte(0),convert.tobyte(0),convert.tobyte(0),convert.tobyte(0),
convert.tobyte(30),convert.tobyte(16),convert.tobyte(0),convert.tobyte(0)};

int index=getsheetindex(filebyte,tmpbyte);
if(index>-1)
{

index+=16+12;
system.collections.arraylist sheetnamelist=new system.collections.arraylist();

for(int i=index;i<filebyte.length-1;i++)
{
byte temp=filebyte[i];
if(temp!=convert.tobyte(0))
sheetnamelist.add(temp);
else
break;
}
byte[] sheetnamebyte=new byte[sheetnamelist.count];
for(int i=0;i<sheetnamelist.count;i++)
sheetnamebyte[i]=convert.tobyte(sheetnamelist[i]);

sheetname=system.text.encoding.default.getstring(sheetnamebyte);
}
return sheetname;
}
/// <summary>
/// 只供方法getsheetname()使用
/// </summary>
/// <returns></returns>
private static int getsheetindex(byte[] findtarget,byte[] finditem)
{
int index=-1;

int finditemlength=finditem.length;
if(finditemlength<1) return -1;
int findtargetlength=findtarget.length;
if((findtargetlength-1)<finditemlength) return -1;

for(int i=findtargetlength-finditemlength-1;i>-1;i--)
{
system.collections.arraylist tmplist=new system.collections.arraylist();
int find=0;
for(int j=0;j<finditemlength;j++)
{
if(findtarget[i+j]==finditem[j]) find+=1;
}
if(find==finditemlength)
{
index=i;
break;
}
}
return index;
}