Unable to Read File When Exporting To Excel In C#
Question
I am using C# exporting data to excel. This works fine at first. The export is triggered via a button event, if the user request several exports from the same page in a row I start to receive the error "Unable to Read File". If I select "SAVE" file instead of open, then it writes the file just fine. It just will not open the file in the browser.
I am fairly certain that the error is coming from Excel, since Excel does open up but will not load my file.
I read about Response.End and Response.Close ... Some say never ever use them some say to use them. I have tried every combination of End and Close.
My gut feeling that that something is being cached in memory, because of I close my browser (or wait for a long time) it seems to clear up the problem.
Does anyone have an idea of what could be wrong, or at least how do I tell why excel is unable to read my file when I can write it and open it from my hard drive without an issue?
protected void btnSaveToXls_Click(object sender, EventArgs e)
{
Response.ClearHeaders();
Response.Cache.SetCacheability(HttpCacheability.Private);
Response.Buffer = true;
Response.AddHeader("content-transfer-encoding", "binary");
Response.Clear();
Response.AddHeader("Content-Disposition", "attachment; filename=myFileName.xls");
Response.AddHeader("pragma", "private");
Response.ContentType = "application/vnd.ms-excel";
using (StringWriter sw = new StringWriter())
{
// The main purpose of these next two writes are to name the worksheet and add the gridlines to the excel sheet
sw.Write(@"<html xmlns:x=""urn:schemas-microsoft-com:office:excel"">");
sw.Write(@"<head>
<xml>
<x:ExcelWorkbook>
<x:ExcelWorksheets>
<x:ExcelWorksheet>
<x:Name>Clients Contacted</x:Name>
<x:WorksheetOptions>
<x:Panes></x:Panes>
<x:Print><x:Gridlines /></x:Print>
</x:WorksheetOptions>
</x:ExcelWorksheet>
</x:ExcelWorksheets>
</x:ExcelWorkbook>
</xml>
</head>");
using (HtmlTextWriter htw = new HtmlTextWriter(sw))
{
Label newLine = new Label();
newLine.Text = "<br/>";
GridView gv = new GridView();
gv.GridLines = GridLines.Both;
gv.HeaderStyle.Font.Bold = true;
//. . .
// a bunch of code here to populate my gridview
//. . .
Panel p = new Panel();
p.Controls.Add(lblTitle);
p.Controls.Add(new Label { Text = "<BR/>" });
p.Controls.Add(lblReportTitle);
p.Controls.Add(new Label { Text = "<BR/>" });
p.Controls.Add(new Label { Text = string.Format("Run Date {0}", DateTime.Now.ToString("MM/dd/yyyy")) });
p.Controls.Add(new Label { Text = "<BR/>" });
p.Controls.Add(new Label { Text = "<BR/>" });
p.Controls.Add(gv);
p.RenderControl(htw);
try
{
// Response.Clear();
sw.Write("</html>");
Response.Buffer = true;
Response.Output.Write(sw.ToString());
// Response.Output.Flush();
Response.Flush();
// Response.End();
}
catch (Exception ex)
{
//... Logging the error ...
}
finally
{
Response.Close();
}
}
}
}
1 answers
solution1
0 2017-10-09 22:00:15
Here is what I found out. The issue seems to be that the second time around you need to wait for the dialog box from IE (that prompts you to "Open", "Save", or "cancel") to change its background color. In my case, it changed from a white background to yellow background. My guess is that the the document was not all the way downloaded to the client before excel tried to open it. Chrome gave me an error if I went too fast, but it opened it anyway, and the file looked fine.
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