Httpresponse - How To Handle Errors When Using C# To Create A Zipfile For Download
Oct 29, 2010
I'm working on a functionality in my asp.net web site that enables the user to download some files as a zip file. I'm using the DotNetZip library to generate the zip file.
Now, if anything goes wrong, say the Utils.ExportToZip method fails, I want to present an error message to the user and not the download dialog. Do I have to remove some data from the Response object in order to cancel the download operation?
I'm writing some code in which I need to use my own HttpResponse object to capture the output from a method on another object that takes an HttpResponse as a parameter. The problem is, this other object (which I cannot modify) calls HttpResponse.End(), which causes an "Object reference not set to an instance of an object" exception to be thrown. What can I do about this?
Dim myStringbuilder As New StringBuilder Dim myStringWriter As New IO.StringWriter(myStringbuilder) Dim myResponse As New Web.HttpResponse(myStringWriter)
someObject.doStuffWithHttpResponse(myResponse) ' calls myResponse.End() and crashes
Here's some more complete information about the error, thrown from the following code in a console application:
Dim myStringbuilder As New StringBuilder Dim myStringWriter As New IO.StringWriter(myStringbuilder) Dim myResponse As New Web.HttpResponse(myStringWriter) Try myResponse.End() Catch ex As Exception Console.WriteLine(ex.ToString) End Try
Here's the text of the exception:
System.NullReferenceException: Object reference not set to an instance of an object. at System.Web.HttpResponse.End() at ConsoleApplication1.Module1.Main() in C:Documents and Settingsjoe.userLocal SettingsApplication DataTemporary ProjectsConsoleApplication1Module1.vb:line 10
I am trying to create an instance of System.Web.HttpResponse to send the uers to another website.I am doing some other stuff in my vb.net that does not let me use the regular Response.Redirect.when I do Dim myRsp As System.Web.HttpResponse = New System.Web.HttpResponseit complains about a textwriter.
We have an ASP.NET page which uses an update panel for partial page postbacks. On the server side, the postback performs some database work and updates several UI elements. The database code is all contained in several transactions, so the state will still be consistent if an exception is thrown. We're working on some error handling code now, and my first thought was to log the exception thrown, reload the last consistent UI state, and show some sort of modal popup or other ui element with a brief error message for the user (this is an intranet page, so we're automatically notified of the bug, and the users know where to find us.
I have an Application_Error handler in my Global.asax file. However, I load many pages using an XHR request and would rather these "sub pages" return javascript or a real 500 code for my main app to process, rather than an error page.
Is it possible to handle errors on certain pages in a different way? Can a master page handle its own errors in a page extending it without bubbling it up to Global.asax?
This morning I found myself dealing with A SQL POOLING ERROR Timeout expired. The timeout period elapsed prior to obtaining a connection from the pool. This may have occurred because all pooled connections were in use and max pool size was reached. I did fix this with resetting my pooling and setting a pooling max =100 Anyway now Im starting to rethink how I open connections, dealing with errors and proper closing of connections Would you say this code below is a good way of opening, closing connections (even when errors occurred)
Dim Connection As SqlConnection Dim myConn As String = (ConfigurationManager.ConnectionStrings("MyConnString").ConnectionString) Connection = New SqlConnection(myConn) Try Dim DBCommand As SqlCommand Dim dt As New DataTable() Dim myDataSet As New DataSet Connection.Open() DBCommand = New SqlCommand("GetAllCategories_", Connection) DBCommand.CommandType = CommandType.StoredProcedure DBCommand.Parameters.Add("@HomePageID", SqlDbType.Int).Value = HiddenChosenVirtualMainID.Value Dim mySqlAdapter As New SqlDataAdapter(DBCommand) mySqlAdapter.Fill(dt) SecondLevelChildDatalist.DataSource = dt SecondLevelChildDatalist.DataBind() Catch ex As Exception 'Error goes here SqlConnection.ClearAllPools() Finally 'close the connction Connection.Close() Connection.Dispose() End Try
I really want to switch over to ajax, but i can't seem to get my error handlling perfect. If i can't handle errors correctly, I just can't use it. What I really want to happen is to do a full refresh of the Top Frame. How I normally do this is by a similar call to Response.Write(<script>top.location.href = ""</script>). I was currently doing this in Global.asax. This becomes a problem when I error out in an AJAX postback. I've also noticed that There is an AsycPostbackErrorHandler you can attach to the ScriptManager. This is all find an dandy, but it will still hit my Global.asax Application_Error Event.
I am honestly just not sure how to handle this.
As I said, the result I want is....To Reload the Top Frame with some Error Message...whether I have to do some weird redirection or whatever. My problem lies specifically with the Global.asax file.
When setting up asp.net error handlers for things like 404 errors, it is more 'efficient' to do this in IIS, or handle it in the Global.asax Application_Error event? I know the latter will be called, and I want to log this information in a database, but should I then just return without any redirect and let IIS do the redirect, or would it be better to do a response.redirect inside application_error once we've logged it?
On my site I put things in Web user controls. For example, I will have a NewsItem Control, an Article Control, a ContactForm control.These will appear in various places on my site.
What I'm looking for is a way for these controls to pass messages up to the Page that they exist on.
I don't want to tightly couple them, so I think I will have to do this with Events/Delegates. I'm a little unclear as to how I would implement this, though.
A couple of examples:
1: A contact form is submitted. After it's submitted, instead of replacing itself with a "Your mail has been sent" which limits the placement of that message, I'd like to just notify the page that the control is on with a Status message and perhaps a suggested behaviour. So, a message would include the text to render as well as an enum like DisplayAs.Popup or DisplayAs.Success
2: An Article Control queries the database for an Article object. Database returns an Exception. Custom Exception is passed to the page along with the DisplayAs.Error enum. The page handles this error and displays it wherever the errors go.
I'm trying to accomplish something similar to the ValidationSummary Control, except that I want the page to be able to display the messages as the enum feels fit.
Again, I don't want to tightly bind or rely a control existing on the Page. I want the controls to raise these events, but the page can ignore them if it wants.I'd love a code sample just to get me started.
I know this is a more involved question, so I'll wait longer before voting/choosing the answers.
I am learning on how to create data access layer code for a web site. I want to ensure I am actually connecting to the datasource, so, I am wanting to use a try/catch block within my data access layer class methods. What I am not sure how to handle is a case where the connectionstate is not open. The method should ideally return a datatable. If an error is thrown would I just return an empty datatable? That is my first thought. My other thought is to return an object and pass a datatable if the connection succeeds or the exception if the connection fails.
i downloaded the ajax control toolkit from codeplex, and followed the instructions to install it on my visual studio toolbox panel. then i just tried to use a calenderextender on a textbox.i get errors. i use visual studio 2008, windows xp sp2, .net 3.5.
this is my code:<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> [code]....
when i run the page , i get the following error on the browser <html
Webpage error details,User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; .NET CLR 2.0.50727; .NET CLR 3.0.04506.648; .NET CLR 3.5.21022; InfoPath.2) Timestamp: Wed, 21 Apr 2010 09:26:51 UTC
Message: AjaxControlToolkit requires ASP.NET Ajax 4.0 scripts. Ensure the correct version of the scripts are referenced. If you are using an ASP.NET ScriptManager, switch to the ToolkitScriptManager in AjaxControlToolkit.dll. Line: 2 Char: 412 Code: 0 URI: http://localhost:1975/LearnAjaxControlKit/ScriptResource.axd?d=7EpUrBYKJUxUvlaCKyczmnwIfd03hNqM0Z73JZEjtiK7woy5vZ9bqIneG9KNiH6H0&t=634064303120000000
Message: Object doesn't support this property or method Line: 2 Char: 9702 Code: 0 URI: http://localhost:1975/LearnAjaxControlKit/ScriptResource.axd?d=7EpUrBYKJUxUvlaCKyczmng9Qst_KL8215GZBigOiAwJKrFNmxZ21M_Z9YzWn1I3_LI-o-OYcARQmvjaTAEzyg2&t=634064303120000000
Message: Object doesn't support this property or method Line: 2 Char: 27077 Code: 0 URI: http://localhost:1975/LearnAjaxControlKit/ScriptResource.axd?d=7EpUrBYKJUxUvlaCKyczmm52CX_RWQFeSM7yLR_r3VD9wTjX79oGHdgUNySBlr8bM4Zb-RdVZFB4R31momZv7g2&t=634064303120000000
Message: 'Sys.Extended.UI.TextBoxWrapper' is null or not an object Line: 2 Char: 456 Code: 0 URI: http://localhost:1975/LearnAjaxControlKit/ScriptResource.axd?d=7EpUrBYKJUxUvlaCKyczmm52CX_RWQFeSM7yLR_r3VD9wTjX79oGHdgUNySBlr8bM4Zb-RdVZFB4R31momZv7g2&t=634064303120000000
I have a simple 'file download' generic handler which sets the response contenttype and headers before sending the file through the same response.
I also have Response.Cache.SetCacheability(HttpCacheability.server) set in the global.asax.
As I have noticed from various sources, Internet Explorer doesn't like this no-cache setting and gives an error when trying to download the file (requested site unavailable or cannot be found).
I thought maybe I could override this setting in the .ashx page, so I alter the response's cacheability setting to public. This did not solve the issue. removing the line from global.asax does solve the problem but obviously affects the whole site.
Is there a way of setting the cachability just for my generic handler?
-Edit- Important: I updated the code to not use obsoluete functions. Now only the NoSuchDirectoryException issue remains
Edit: NOTE i can bypass the NoSuchDirectoryException by creating the folder in a winform app and copy it. However i still have a LockObtainFailedException issue if i dont shut down properly.I have an issue with (Lucene.net 2.9.2
[https://svn.apache.org/repos/asf/lucene/lucene.net/tags/]. It throws a lock exception. After poking around i notice these things.
My code below works in an app bit when calling in Application_Start i get a NoSuchDirectoryException.Not closing the writer (as my code doesnt do below) i WILL get a LockObtainFailedException with the message
Lock obtain timed out: SimpleFSLock@<FULL_PATH> from either app or asp.net
These thread hinted when spawning threads they get less permissions then i do (but! my main thread has problems as well...) and one solution is to impersonate IIS. I am using visual studios 2010. I am not sure how full blown it is but my attempt to impersonate it failed.
So my question is how do i have lucene create the directory and not throw an exception if dont close the writer for some reason (such as power going out)?
I have a C# web forms ASP.NET 4.0 web application that uses Routing for URLs for some reason custom errors defined in the system.web section of my web.config is entirely ignored and it will fall back the IIS errors.
This gets entirely ignored
[code]....
This would be a minor inconvenience except that by the fact it falls back to IIS native instead of my application it completely circumvents Elmah logging my 404 exceptions correctly.
Sometimes I am getting a time out exception when reading an XML via a URL. Is there something I can do to prevent this, or is this a problem with the remote server? Below is my simple code:
XmlDocument doc = new XmlDocument(); doc.Load(XmlReader.Create(this.RssUrl));
I do not know how to pass that setting into the code above (or if that is even the correct solution): [URL]
Exception Details: System.Net.WebException: The operation has timed out
I am trying to create one subroutine that can handle all deletes for a web app. I have one delete popup panel in my master page, and I call it each time from my content pages. When an instance of delete is called from a content page, I store the name of a delete subroutine specific to the delete instance in a session variable and popup the delete panel in the master page. If a user types YES into a delete textbox in delete popup panel, a confirmDelete Subroutine in codebehind of the Masterpage is called. When the confirmDelete subroutine in the Masterpage is callled, I want to call a subroutine in the content page that has the name stored in the session variable. What is the simplest way to do that?
I am trying to create a method that accepts multiple types of controls - in this case Labels and Panels. The conversion does not work because IConvertible doesn't convert these Types.
public void LocationsLink<C>(C control) { if (control != null) { WebControl ctl = (WebControl)Convert.ChangeType(control, typeof(WebControl)); Literal txt = new Literal(); HyperLink lnk = new HyperLink(); txt.Text = "If you prefer a map to the nearest facility please "; lnk.Text = "click here"; lnk.NavigateUrl = "/content/Locations.aspx"; ctl.Controls.Add(txt); ctl.Controls.Add(lnk); } }
I need to create a button, which when clicked shows the download pop up box, but I don't know how, and would be grateful if someone could show me how? The box needs to work with any file type, the file name will be based upon a value from a database.
