Obtain the results returned by confirm based on the background code before executing the background code)

Typical applications:
Create a file: First, check whether the file on the server exists. If yes, a prompt box is displayed: Do you want to overwrite the file? If you confirm to overwrite, the new file will be created; otherwise, the system will directly return
Solution:
Add two buttons, one of which is hidden:
<Input type = button runat = server id = btnchk value = "Create File" onserverclick = "btnchk_serverclick"/>
<Input type = button runat = server id = btncrtfil onserverclick = "btncrt_serverclick" style = 'visibility: Den den '/>

Main btnchk_serverclick eventsCodeAs follows:

Crtfilchk (filename, ' Btncrtfil ' , Page );
The main code of the btncrt_serverclick event is as follows:
Createfile (filename, page );

First, determine if _ dopostback is used to call the code of the control on the server.

Public   Void Crtfilchk ( String Strfilename, String Hidcontrolid, page srcpage)
{
Try
{
String Strtmp = "" ;
// Delete old files
If (File. exists (strfilename ))
{
Strtmp = Strfilename. Replace ( " \\ " , " / " );
Srcpage. registerstartupscript (system. guid. newguid (). tostring (),
" <SCRIPT> If ('overwrite? ') {__ Dopostback (' " + Hidcontrolid + " ', '') ;}</SCRIPT> " );
}
Else
{
Createfil (strfilename, srcpage );
}
}
Catch (Exception E)
{
Httpcontext. Current. response. Write ("<SCRIPT defer> alert ('Operation failed because"+E. Message+"') </SCRIPT>");
}
}

Create a file

Public   Void Createfile ( String Strfilename)
  {
Strfilename = Strfilename. Replace ( " \\ " , " / " );
Try
{
// Delete old files
If (File. exists (strfilename ))
{
File. Delete (strfilename );
}

String Strtmp = " File Content. " ;
Streamwriter SW =   New Streamwriter (strfilename, False , System. Text. encoding. getencoding ( " Gb2312 " ));
Sw. Write (strtmp );
Sw. Close ();

Httpcontext. Current. response. Write ( " <SCRIPT defer> alert ('create a file "   + Strfilename +   " Successful! ') </SCRIPT> " );
}  
Catch (Exception E)
{
Httpcontext. Current. response. Write ( " <SCRIPT defer> alert ('create a file "   + Strfilename +   " Failed because " + E. Message + " ! ') </SCRIPT> " );
}
}

Conclusion: Use _ dopostback to call the code of the server control