I have both asp.net server button controls and html buttons in my asp.net web form.
<asp:LinkButton runat="server" ID="btnExportToExcel" OnClick="btnExportToExcel_Click">Excel</asp:LinkButton>
<button type="submit" class="btn btn-info btn-block">Refresh</button>
I use asp.net button OnClick event to send back an Excel file. Below is the code:
protected void btnExportToExcel_Click(object sender, EventArgs e)
{
Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
Response.AddHeader("content-disposition", "attachment; filename=ExcelDemo.xlsx");
Response.BinaryWrite(ExcelHelper.GetByteArray(datatable));
Response.End();
}
The export to Excel works perfectly fine, but after the export is done, all html buttons start to cause a postback with target id of the asp.net button control responsible for the Excel export, i.e. the OnClick event of btnExportToExcel button is fired again and I get the same Excel file exported again.
Am i doing something wrong with the responce in the OnClick event? Or am I missing something else?
NB. I can fix the problem by using just asp.net buttons, but I would like to understand the nature of the problem.
EDIT. After the reply from Igor, is it correct that the problem has nothing to do with the Response (i.e. I thought that the Response might be missing something) and it could be considered as an expected behavior and I need to be careful with the buttons I use?
This is what happens on your page:
asp:LinkButton is clicked. On its client-side click it calls __doPostBack that sets hidden __EVENTTARGET input value to btnExportToExcel.
The form is submitted to the server. Browser is waiting for the new content to arrive.
The new content is a downloadable file, so the browser page is not cleared and stays what it was during the submit.
Clicking on any button with type="submit" causes the form submission with __EVENTTARGET still having btnExportToExcel value.
Server-side page interprets POST request with Request.Form["__EVENTTARGET"]="btnExportToExcel" as the click of btnExportToExcel.
I'm missing a Response.Clear at the beginning.
protected void btnExportToExcel_Click(object sender, EventArgs e)
{
Response.Clear();
Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
Response.AddHeader("content-disposition", "attachment; filename=ExcelDemo.xlsx");
Response.BinaryWrite(ExcelHelper.GetByteArray(datatable));
Response.End();
}
Add OnServerClick="return false;" to the button markup, to avoid the postback
Related
So I'm working with this form which, at the end, generates a Word document for the user to download, fires off some emails, and then displays a success panel for the user. The problem I'm having is that the .Visible flags don't end up getting changed whenever I call the downloadWordFile() method. Is there something in that method that would be messing with my ability to change visibility of ASP panels? I've tried removing almost every part of this to see where the issue is popping up and I haven't been able to make heads or tails of it. Everything else works fine, it's just this method causing the issue. Thanks in advance for your help!
protected void btnSubmit_Click(object sender, EventArgs e)
{
pnlForm.Visible = false;
pnlSuccess.Visible = true;
email();
adminEmail();
downloadWordFile();
}
protected void downloadWordFile(){
Response.ContentType = "application/msword";
Response.ContentEncoding = System.Text.UnicodeEncoding.UTF8;
Response.Charset = "UTF-8";
Response.Write("<html xmlns:o='urn:schemas-microsoft-com:office:office' xmlns:w='urn:schemas-microsoft-com:office:word' xmlns='http://www.w3.org/TR/REC-html40'>");
Response.Write("<head>");
Response.Write("<META HTTP-EQUIV=\"Content-Type\" CONTENT=\"\"text/html; charset=UTF-8\"\">");
Response.Write("<meta name=ProgId content=Word.Document>");
Response.Write("</head>");
Response.Write("<body>");
Response.Write("<div class=Section2>");
Response.Write(buildForm());
Response.Write("</body>");
Response.Write("</html>");
Response.AppendHeader("Content-Disposition", "attachment; filename=" + "Generic.doc");
HttpContext.Current.Response.Flush();
}
EDIT 1: I ended up going a different route entirely. Rather than trying to switch panels, generate emails, and generate word files all in one go, I made the submit button switch the panels, and the success panel now shows a preview of the word document to be downloaded and provides the user a chance to make changes. There is a download button on the success panel that generates the emails and downloads the word document. This required minimal changes to the way the code was already set up and solved another problem I was having with the email generation.
A response can only be one thing. You can't respond with page content and a file. You are setting the response to a file so that is how the browser handles the response.
I would handle this situation by the calling a JavaScript function in the button's click event that downloads the file via an IFrame.
First you would need a "download file" page. In the OnLoad event of that page you can call email();, adminEmail(); and downloadWordFile();
The JavaScript click event handler would look something like this.
function DownloadFile() {
var downloadFrame = document.createElement("IFRAME");
if (downloadFrame != null) {
downloadFrame.setAttribute("src", 'DownloadFile.aspx');
downloadFrame.style.width = "0px";
downloadFrame.style.height = "0px";
document.body.appendChild(downloadFrame);
//Set the visibility of pnlForm and pnlSuccess
}
}
EDIT:
Per your comment, I've had to do the same thing. I solved it by posting the form as normal and assembling the form values into a query string. Then use ScriptManager.RegisterStartupScript to add a script that calls the DownloadFile() function when the page loads. The DownloadFile() function takes the query string as a parameter and the DownloadFile.aspx page uses it to get the form data.
So the click event handler would be updated like this.
function DownloadFile(queryString) {
var downloadFrame = document.createElement("IFRAME");
if (downloadFrame != null) {
downloadFrame.setAttribute("src", 'DownloadFile.aspx' + queryString);
downloadFrame.style.width = "0px";
downloadFrame.style.height = "0px";
document.body.appendChild(downloadFrame);
//Set the visibility of pnlForm and pnlSuccess
}
}
So I have a button inside my gridview. If the user clicks on the button a rowcommand is send and a pdf file is downloaded / written to the response.
Code
HttpResponse httpResponse = Response;
httpResponse.Clear();
httpResponse.ContentType = "application/pdf";
httpResponse.AddHeader("content-disposition", $"attachment;filename={rowData.Pod.fileName}");
httpResponse.Output.Write(bytes);
Response.Flush();
HttpContext.Current.ApplicationInstance.CompleteRequest();
For some reason I always get Server cannot set content type after HTTP headers have been sent. when tried to download the file. Now the gridview is in a updatepanel but that should not be a problem since other buttons for downloading work.
I have also tried to send the buffer to true before I did the file download but that did not change it.
EDIT
The problem was that there was still an async postback that I had setup on the 'selectedindexchanged' of the gridview to display a modal. Is there any way I can work around this? When I change the trigger the whole page reloads before showing the modal and also resprings. The file downloads after changing it to postback instead of asyncpostback
I had an issue that was extremely similar to this. I had a button inside a ListView control that was trying to print a pdf report. After extensive research I found a very simple solution.
Add OnInit="btnPrint_Init" to the button on the front of the page and then add the following to the code behind (change the name of the button to suit your needs):
protected void btnPrint_Init(object sender, EventArgs e)
{
Button btnPrint = (Button)sender;
ScriptManager.GetCurrent(this).RegisterPostBackControl(btnPrint);
}
Probably, Response.Buffer is false.
You should write the content after writing the headers.
httpResponse.ContentType = "application/pdf";
httpResponse.AddHeader("content-disposition", $"attachment;filename={rowData.Pod.fileName}");
httpResponse.Output.Write(bytes);
Actually, you can instead set a JavaScript command to those buttons requesting an http handler which is the best practice for downloading a file.
For security reasons you can create a guid and put the guid to session items for each row (having the file id as the value) and then send that guid to the http handler and retrieve the file id from session and response binary write the file
I have the following code to download a file from the server to the client, that occurs when the button btnSavetoDB_ExportToExcel is clicked, after that I want to have the button disable, how can I achieve that?
string fileName = newFN + ".xlsx";
Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
Response.TransmitFile(DestFile);
Response.End();
btnSavetoDB_ExportToExcel.Enabled = false;
I noticed that the button did not become disable when placed the above code (Response), cause I had another code there and the button became disable with it. So it must be something related with the Response.
EDIT:
The button is within a ModalPopupExtender in case it matters.
The reason for this is that if you disable the button with server code you need to return the response to the browser window.
Here you return a stream that is captured by the browser as a file instead of to the browser window so the current display is never updated.
To get around this you can implement a javascript line on the button in the html itself.
You can use Attribute.Add() in code at Page_Load, f.ex:
btnSavetoDB_ExportToExcel.Attribute.Add("onclick","this.disabled=true")
There at least two possible solutions.
1) Instead of writing a file to the response you can generate file in the temp directory on the server and give the user the link to this file (or redirect to this link).
2) If you want use writing to the response, you can create new Generate.aspx page that writes the file to the response in its Page_Load method.
if (Request.QueryString["ID"] != null)
{
//find file by its ID
...
Response.AddHeader("Content-disposition", "attachment; filename=" + fileName));
Response.ContentType = "application/octet-stream";
Response.WriteFile(fullFileName);
Response.End();
}
On page with your btnSavetoDB_ExportToExcel in Page_Load add this code:
var script = #"<script language=JavaScript>function Export(fileID)
{
var iframe = document.createElement('iframe');
iframe.src = 'Generate.aspx?ID='+ fileID;
iframe.style.display = 'none';
document.body.appendChild(iframe);
}
</script>";
Page.RegisterStartupScript("Startup", script);
And then just call javascript Export method to send file to the user.
As mentioned in the other answer, the button should be disabled in client side (since you are using Response.End() in your code, ASP.NET will never render the page with the button having Enabled=False.
In your .aspx file add
<asp:Button ID="btnSavetoDB_ExportToExcel" OnClientClick="this.disabled=true;" [..] />
But also note that this might not be a good idea altogether - what if the user accidentally clicks "Cancel" from the file download window?
A better solution (understanding that you want to prevent the user from clicking the button multiple times) is to add a timer to re-enable the button:
<asp:Button ID="btnSavetoDB_ExportToExcel" OnClientClick="var a=this; a.disabled=true; window.setTimeout(function() { a.disabled=false; }, 5000)" [..] />
Value 5000 is the time in miliseconds after which the button will be re-enabled.
I have found the solution to my problem, credit goes to: Dave Ward (click here)
<asp:Button ID="btnSavetoDB_ExportToExcel" runat="server"
OnClientClick="this.disabled = true;"
UseSubmitBehavior="false"
Text="Save results to DB and export to Excel"
onclick="btnSavetoDB_ExportToExcel_Click" />
this does the trick:
OnClientClick="this.disabled = true;"
UseSubmitBehavior="false"
I'm having trouble getting my ASP.Net page to return CSV on submit being clicked. Here's the asp button definition I have for the submit button in Form.aspx:
<asp:Button id="submitreport" name="submitbutton" text="submit" OnClick="Report_Submit" runat="server" />
And this is the corresponding function in Form.aspx.cs:
public void Report_Submit(object sender, EventArgs e) {
Debug.WriteLine("GETS HERE?");
Response.Charset = "UTF-8";
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetAllowResponseInBrowserHistory(true);
Response.ContentType = "text/csv";
Response.AddHeader("Content-Disposition", "attachment; filename='" + DateTime.Today.ToString() + ".csv'");
Response.Write("test,output");
Response.End();
}
When this is ran in Visual Studio I don't even see the debug print line. Does anybody know what's wrong with my setup?
Edit: I know for certain that the pages are set up right because if I put a breakpoint on my empty Page_Load function in Form.aspx.cs VS does break there. Besides that the breakpoint at the debug write line is skipped over on the form submit and the same page is returned again.
Update By creating a new project with just the button and the handler the Report_Submit() function is called and the CSV file is correctly generated. Since that narrows it down a little bit, does anybody know what could be going on in my other VS 2008 project that's causing this not to work?
I found a pretty good work around that returns a .csv file (which also shouldn't be quoted in my header creating function calls, but that wasn't the problem). In addition, the shouldn't specify a name since ASP.NET fills that in, but that also wasn't the problem.
Moving just the relevant form processing code into its own project worked just fine, but my project was too large to manage that.
The workaround I found useful is to just move the button handling function into Page_Load() and use:
if(Request.HttpMethod == "GET") {
Debug.WriteLine("this is just a request for the page"):
}
else if(Request.HttpMethod == "POST") {
Debug.WriteLine("processing the form");
//rest of code...
}
else {
//some HTTP action that doesn't matter
}
to distinguish page requests (GET) from users entering the form (POST requests).
My problem looks like this.
I have a grid with documents (Id's). Now when somebody clicks at a row I would like to allow him to download or show that document. But to make it esier let's say that I would do this on a button click. I tried two approaches but none of them worked form me.
I tried to response.binarywrite on the button click:
Response.Clear();
Response.ClearHeaders();
Response.ClearContent();
Response.ContentType = "application/postscript mime";
Response.AddHeader("content-disposition", "attachment; filename=test.ps");
Response.AddHeader("content-length", _excuteGetDocumentResult.Length.ToString());
Response.ContentEncoding = new System.Text.UTF8Encoding();
Response.BinaryWrite(_excuteGetDocumentResult);
But nothing happens and when I try to modify this code I usually get some javascript errors saying sommething about changing the response...
The socond approach was opening new window and on page load adding the code above.
<asp:Button Text="ShowResult" OnClientClick="radopen('ShowResult.aspx','ShowDocumentDialog'); return false;"
runat="server" />
The socond approach works but my opened window still exists after saving or canceling the explorer saving file dialog window. I tried to add some javascript to close it but it only works where there is no response.binarywrite on the load page...
Any ideas how I can achive what I want?
In method 1.
try Response.End(); after Response.BinaryWrite(_excuteGetDocumentResult);