How to Export Data to Excel from an ASP.NET Application + Avoid the File Format Differ Prompt

Artigo
01/30/2009

This is a common task for ASP.NET developers. You have a Web application where you expose data from a database, Web service, or third-party API and you need an "Export to Excel" button. I have used different approaches to export to Excel from a Web application. Here's some options and guidance of when to use each one.

Generate a CSV file: If you open a CSV file in Excel, you can see a table with data. You can use this approach if you don't need control over formatting, styles, or workbook structure. I have used this approach when I pull data from a data source and I don't need to render it on the browser. For example, you are working on a stock options solution and you connect to a Web service that pulls stock market prices. Your users don't want to see detailed stock information on a browser and prefer that you generate and Excel file where they can pivot stock prices.
Generate an XML file: (with or without an XSLT, depending if you want to control the schema). Have you opened an XML file in Excel? This is pretty cool. Excel allows you to open XML files with our without a schema. You can also see a table of data in Excel and can have some control on formatting if you use a schema. I have used this approach when I have a data source that is already in XML format.
Generate from GridView: I like this one a lot and I think it's a common practice between ASP.NET developers. Some page forms in ASP.NET Web applications display data in data controls. The GridView is a popular control that displays data in a table format. You can use it to bind to data source controls, such as SqlDataSource. You can export to Excel from a GridView using a StringWriter and an HtmlTextWriter. You can use this approach if you already have a page with a GridView. You already did a round-trip to get the data from any given source, so why do it twice? The issue is that you have little control over formatting, style, or workbook structure.
Generate an Excel file using the Open XML SDK 2.0 : If you use this approach you gain absolute control of the spreadsheet format and content. For example, you can generate a worksheet with a table and another one with a chart based on the same data source. You can have control over formats, styles, content, and document structure. Zeyad has a great post where he provides a detailed sample for this approach: Document Assembly Solution for SpreadsheetML.

Note: I can't stop to mention the big no-no… using the Excel PIA to generate a spreadsheet server-side. This is not a good practice and it's not recommended or supported, so let's forget about this one.

Now, for those of you who are working with any of the first three approaches, you may have seen the prompt of file format differ each time you export to Excel.

You get this message because you are opening a file in Microsoft Office Excel 2007 that contains content that does not match the files extension.

I am not very annoyed about this, but I know some people are. By default, a user can decide whether to open the file when the warning message is displayed, but you can control user-notification either:

Updating the registry if you need to control the user-notification on a few PCs.
Using a Group Policy Setting if you need to control the user-notification on lots of PCs.

Here's a KB article that provides detailed steps for both options: When you open a file in Excel 2007, you receive a warning that the file format differs from the format that the file name extension specifies.

Here's a quick code sample in C# for approach 3 (Export from GridView) that you can use to export to Excel. I changed my registry following the steps explained in the previous article and it worked like a charm. No prompt!

<%@ Page Language="C#" AutoEventWireup="true" EnableEventValidation="false" %>

<%@ Import Namespace="System.IO" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="https://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title>Export to Excel - GridView Sample</title>
</head>

    // Get files from selected path
    private void BindFiles() {
DirectoryInfo di = new DirectoryInfo(tbPath.Text);
        gvFiles.DataSource = di.GetFiles();
        gvFiles.DataBind();
    }

protected void btnExportToExcel_Click(object sender, EventArgs e) {
ExportToExcel();
}

    //Export to Excel from a GridView
    protected void ExportToExcel() {
Response.Clear();
        Response.Buffer = true;
        Response.ContentType = "application/vnd.ms-excel";
        Response.AddHeader("content-disposition", "attachment;filename=MyFiles.xls");
        Response.Charset = "";
this.EnableViewState = false;

System.IO.StringWriter sw = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter htw = new System.Web.UI.HtmlTextWriter(sw);

gvFiles.RenderControl(htw);

        Response.Write(sw.ToString());
        Response.End();
    }

protected void Page_Load(object sender, EventArgs e) {
BindFiles();
}

public override void VerifyRenderingInServerForm(Control control) {
}

</script>

<body>
    <form id="form1" runat="server">
    <div>
        <h1>
My Files</h1>
        <table border="0" cellpadding="0" cellspacing="0" style="width: 100%; height: 12%">
            <tr>
                <td>
Path:
                </td>
                <td>
                    <asp:TextBox ID="tbPath" runat="server" Width="600px" Text="C:/"></asp:TextBox>
                </td>
            </tr>
            <tr>
                <td>

                </td>
                <td>
                    <asp:Button ID="btnExportToExcel" runat="server" Text="ExportToExcel"
onclick="btnExportToExcel_Click" />
</td>
            </tr>
        </table>
    </div>
    <asp:GridView ID="gvFiles" runat="server">
    </asp:GridView>
    <br />
</form>
</body>
</html>

Happy Friday!

Comments

Anonymous
January 30, 2009
PingBack from http://www.clickandsolve.com/?p=2418
Anonymous
January 30, 2009
Thank you for submitting this cool story - Trackback from DotNetShoutout
Anonymous
February 15, 2009
Hi, Thanks for your Article. Its really nice one. Can you tell me how to export a dataset containing multiple tables to excel. I think this refers to your second approach.
Anonymous
March 11, 2009
Combine/Compress/MinifyJSandCSSfilesinASP.NETMVCHowtoExportDatatoExcelfromanASP.NET...
Anonymous
March 11, 2009
Combine/Compress/Minify JS and CSS files in ASP.NET MVC How to Export Data to Excel from an ASP.NET Application
Anonymous
August 05, 2009
Nicely written. Thanks for the article.
Anonymous
August 11, 2009
Hi, My DataSet contains value 002 whenever i download in DataSet to Excel. It shows only 2 but i need the following format 002 in Excel download file(Using ASP.Net-05, C#). Is it possible. Please help me.
Anonymous
August 25, 2009
The comment has been removed
Anonymous
September 22, 2009
Great, but can we export 2 tables(gridviews) in to 1 excel file to 2 sheets?
Anonymous
December 02, 2009
Your code produces the following error: RegisterForEventValidation can only be called during Render();
Anonymous
December 11, 2009
The comment has been removed
Anonymous
February 09, 2010
i wann to know how to insert the image in to the excel sheet once i click the button .............
Anonymous
March 19, 2010
Hi, when exported to excel, it shows a pop-up with an 'Open' and 'Save' option. Click open - this opens the excel sheet with the content. Go to Files - 'Save as' option - you get to see 'Save as type' defaulted to 'Web Page(*.htm; *.html)' How do we change the Default File Type to Excel? Thanks in advance...
Anonymous
March 31, 2010
What is the purpose of this.EnableViewState = false; in the ExportToExcel() method?
Anonymous
April 02, 2010
The comment has been removed
Anonymous
April 27, 2010
Hi, Thanks for this useful post. It is working fine when Ms-Office is installed but when Ms-Office is not installed it is asking for program to open this. Please reply to solve this problem. Thanks
Anonymous
June 03, 2010
The comment has been removed
Anonymous
June 03, 2010
NA MADDA KATLA VUNDI RA POOKA NICE
Anonymous
August 25, 2010
No lah. It's still prompt even after i tested with you code!. Please help me out as i faced with same problem 'Prompt Message' in excel after export from grid view. Thanks
Anonymous
November 30, 2010
It's still shows the prompt message "The file you are trying to open in different format.....".Please help me about this.
Anonymous
January 19, 2011
The comment has been removed
Anonymous
January 26, 2011
Option 2 is the best for ASP.Net Web Apps. Options 1 and 3 are easy. However, there are no formatting options and they don’t support multiple worksheets. Option 4 is the most powerful. However, it requires saving files to the server, granting privileges to the Excel Interop object and killing the Excel process on the server. For me, this became a big mess. Option 2 allows for formatting and supports multiple worksheets. However, it requires the creation and maintenance of an xslt file. The requirement was to display a dataset with 3 data tables in an Excel workbook and have each data table in its own worksheet. Option 2 worked perfectly.
Anonymous
February 08, 2011
Is there a way to export to excel 2007 instead of doing registry edit to suppress the prompt?
Anonymous
February 08, 2011
It's not good to ask users to do registry edits.
Anonymous
April 12, 2011
I want the file will save from a perticuler place. In short I don't want the pop up will show .The Excel will save in some place automatically. Can any 1 suggest me how to do that ? Awaiting for reply. Thanks
Anonymous
April 22, 2011
yet another nice library to export to excel in nice formatted way: officehelper.codeplex.com
Anonymous
June 06, 2011
my problem is i cannot export more than 0.5 mb of data to excel.i have used same code as above. Please reply if u have any solution.
Anonymous
July 10, 2011
Hi, Any idea how i can export just a simple DIV into excel?
Anonymous
July 14, 2011
nice post, simple and easy to understand
Anonymous
August 08, 2011
for exporting data to excel from an ASP.NET Best way to using Spire.XLS, easy and fast. www.e-iceblue.com/.../excel-for-net-introduce.html
Anonymous
August 17, 2011
Thanks for sharing this, it is really useful for me, also have a look at this link <a href='zeeshanumardotnet.blogspot.com/.../creating-reports-in-excel-2007-using.html& Reports in Excel 2007 using EPPlus (Header, Footer, Comments, Image, Formatting, Shape and Formula)</a>
Anonymous
September 01, 2011
I have a 15 digit number that automatically appears in an exponential formate when exported to excel from an ASP.NET app. Is there a way to show the number in a text format or even a numerical format that isn't exponential?
Anonymous
November 02, 2011
Thanks for this article. I have requirement like. I have 4 gridview in a page. I want to export all of them in a excel workbook. Each grid should be exported in seperate sheet. How can I achieve this??
Anonymous
November 22, 2011
Alternatively, you can use the OpenXML libraries, and export to an Excel 2007 file. The following page shows how to do it, for free, with full source code. www.mikesknowledgebase.com/.../ExportToExcel.htm In answer to a question from Feb 2009, this library will create one Excel worksheet of data per DataTable in your DataSet. It even shows how to then open the Excel file, from your ASP.Net C# code. Very cool.
Anonymous
November 22, 2011
Great article for outlining the various ways of Exporting to Excel. I tried the sample code but got the following error when running: RegisterForEventValidation can only be called during Render(); This can be solved by either setting the EnableEventValidation flag to FALSE in the Web.Config in the following way <pages enableEventValidation ="false"></pages> This will apply to all the pages in your website. Otherwise you can also set it in the @Page Directive of the page on which you are experiencing the above error. <%@ Page Language="C#" AutoEventWireup="true" EnableEventValidation = "false" see www.aspsnippets.com/.../RegisterForEventValidation-can-only-be-called-during-Render.aspx
Anonymous
February 15, 2012
private void Export() { Response.Clear(); Response.AddHeader("content-disposition", "attachment;filename=OrderList.xls"); Response.Charset = ""; Response.ContentType = "application/vnd.xls"; StringWriter StringWriter = new System.IO.StringWriter(); HtmlTextWriter HtmlTextWriter = new HtmlTextWriter(StringWriter); gdLIst.RenderControl(HtmlTextWriter); Response.Write(StringWriter.ToString()); Response.End(); }
Anonymous
February 24, 2012
This is just light wrapper library around the Open XML SDK: officehelper.codeplex.com/documentation
Anonymous
May 06, 2012
superb work Erika Ehrli..fan of uu
Anonymous
August 02, 2012
how to export complete div tag including charts.
Anonymous
January 15, 2013
Good article for beginners. But there one problem. It does not write into ".xlsx" files, which are newer version. Try the below link for exporting data into all versions of excel. www.encodedna.com/.../asp.net-export-to-excel.htm Thank you
Anonymous
April 05, 2013
how to export to excel by using ASP.NET application?
Anonymous
April 28, 2013
check here some more automations with asp.net excel asp.net-informations.com/.../asp-excel.htm gail
Anonymous
June 15, 2013
in my web application i need to export data to excel from datatable in a particular format this has been done i need to lock some cells range to prevent editing in excel sheet i tried but it doesnot get locked ExcApp = New Excel.Application ExcWS = ExcApp.Worksheets("SHEET1") ExcWS.Range("A1", "C3").Locked = True ExcWS.Protect(False, False, False, False, False, False, False, False, False, False, False, False, False, False, False, False) i have above

i need to display checkbox against each supplier no displayed in the sheet & when few of the suppliers are checked , need to import the checked data in the database

Anonymous
August 11, 2013
The comment has been removed
Anonymous
September 17, 2013
find this easy way of import asp.net-informations.com/.../asp-excel-export.htm asp.net excel export lev.
Anonymous
October 14, 2013
Export GridView data to excel from .NET applications, www.kettic.com/.../gridview_data_export.shtml
Anonymous
October 15, 2013
As imple example asp.net-informations.com/.../asp-excel-export.htm export asp.net to excel Bona
Anonymous
November 10, 2013
Getting this error :"RegisterForEventValidation can only be called during Render(); ". Im using vs 2008
Anonymous
December 03, 2013
The comment has been removed
Anonymous
April 29, 2014
very informative. thanks I have found another example for the same to excel refer to www.etechpulse.com/.../exporting-div-dynamic-content-to-excel.html
Anonymous
July 16, 2014
Thanks for your article.:)
Anonymous
October 01, 2014
what is gvFiles, in gvFiles.RenderControl(htw);
Anonymous
February 25, 2015
Thanks for the good article. Keep up the good work.
Anonymous
April 29, 2015
The code here for exporting from grid view does not work for me. I am getting HTML output into the excel file, rather than just column headings and data and Excel fails to open it.

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How to Export Data to Excel from an ASP.NET Application + Avoid the File Format Differ Prompt

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