Question

I already know, codes after the Response.End() will not work. I am trying to alert a message box after Response.End. Basically what i am doing is i will read data from Excel file and check for the missing data in the excel file. I will collect all the data that was missing from the Excel file and write them all to a text file and will prompt that using the following code

string strPath = Server.MapPath("ErrorLog") + "\\" + "ErrorLog.txt";
string FileName = "Errorlog" + ".txt";
string[] createText = { sb.ToString() };
File.WriteAllLines(strPath, createText);
HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment; filename=" + FileName + "");
strPath.Length.ToString());
HttpContext.Current.Response.ContentType = "application/text";
HttpContext.Current.Response.WriteFile(strPath);
HttpContext.Current.Response.End();

After this i would like to display an alert box saying some thing like Invalid Data. But i would like to know how can i do that after Response.End

// Updated code as per lcarus

string strPath = Server.MapPath("ErrorLog") + "\\" + "ErrorLog.txt";
string[] createText = { sb.ToString() };
File.WriteAllLines(strPath, createText);
ClientScriptManager CSM = Page.ClientScript;
string strconfirm = "<script>if(window.confirm('Excel file has Invalid data.')){window.location.href='/Excel1/ErrorLog/ErrorLog.txt'}</script>";
 CSM.RegisterClientScriptBlock(this.GetType(), "Confirm", strconfirm, false);

Answer 1

You need to do this in sort of 2 parts:

Collect the missing data, save it to a file (By the way, you need to create a unique name for the log file unless you are planning to support only one concurrent user on your site) and use ClientScript.RegisterStartupScript to call a function like this:

ClientScript.RegisterStartupScript(this.GetType(),"somekey",
"alert('Some data missing!'); window.location.href='http://your_site.com/path_to_log_file'",true); 

You will know path_to_log_file since you are the one generating it on the server side.

The user will see the alert and after clicking “OK” the log file will be displayed on his browser or asked to download it, depending on whether the browser knows how to handle the file (this is usually determined by the extension of the file).

UPDATE

Sample HTTPHandler implementation.

You can construct the link like this from code behind:

window.location.href='FileDownloader.ashx?FileName=ErrorLog.txt'

public class FileDownloader: IHttpHandler
{
       public bool IsReusable
       {
            get { return true; }
       }

       public void ProcessRequest(HttpContext context)
       {
            // This is where you read the log file and add the content disposition
            //header
            string strPath = Server.MapPath("ErrorLog") + "\\" + context.Request.QueryString["FileName"];

            context.Response.AddHeader("Content-Disposition", "attachment; filename=" + context.Request.QueryString["FileName"] + "");
            strPath.Length.ToString());
            context.Response.ContentType = "application/text";
            context.Response.WriteFile(strPath);
            context.Response.End();

       }
}