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  • C#: When should I use TryParse?

    - by zxcvbnm
    I understand it doesn't throw an Exception and because of that it might be sightly faster, but also, you're most likely using it to convert input to data you can use, so I don't think it's used so often to make that much of difference in terms of performance. Anyway, the examples I saw are all along the lines of an if/else block with TryParse, the else returning an error message. And to me, that's basically the same thing as using a try/catch block with the catch returning an error message. So, am I missing something? Is there a situation when this is actually useful?

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  • Detecting GWT RichTextArea 'dirty' state

    - by David
    I want to detect when the contents of my GWT RichTextArea become 'dirty' (have been changed by the user) in order to enable a 'save' button accordingly. I suppose I could listen for key presses that are likely to have changed the contents; but browser support for key presses is notoriously quirky. I suppose I could, before editing begins, save the original contents in a variable, and upon key press, compare the current contents against that variable, but doing that on each key press is going to be really slow. Is there some neat way to achieve RichTextArea dirty-detection?

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  • Thoughts on try-catch blocks

    - by John Boker
    What are your thoughts on code that looks like this: public void doSomething() { try { // actual code goes here } catch (Exception ex) { throw; } } The problem I see is the actual error is not handled, just throwing the exception in a different place. I find it more difficult to debug because i don't get a line number where the actual problem is. So my question is why would this be good? ---- EDIT ---- From the answers it looks like most people are saying it's pointless to do this with no custom or specific exceptions being caught. That's what i wanted comments on, when no specific exception is being caught. I can see the point of actually doing something with a caught exception, just not the way this code is.

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  • Asp.net error object not set to a reference

    - by Frank
    Hi all, Because I rush in development (a lot of whip cracking here) and declare my objects at the top of the function and instantiate inside my try-catch block, I get a lot of the good old "object not set to an instance of an object" errors while doing TDD, and later if I do miss a branch that object was used in (doing VB now, would prefer C#) or just in every day coding, object not set to an instance of an object is a bit vague. Sure the stack trace sends me to the line the error occured at, but it would be nice if I could modify my logging to either name the object or its type because sometimes I have multiple objects on the same line. It's not the end of the world, but in the end it would save me a few minutes each day. Any ideas on how I can pass the info on which object wasn't set? Thanks

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  • c# eventhandling error

    - by bragin.www
    i have method private void getValues(object sender, EventArgs e) { int id = int.Parse(dgvTable.Rows[dgvTable.CurrentRow.Index].Cells[0].Value.ToString()); var values = from c in v.db.TotalDoc where c.TotalID == id select c.TotalAmount; dgvValues.DataSource = values; } and datagridview "dgvTable" error at this line dgvTable.CellClick += new EventHadler(getValues); error text is: No overload for 'getValues' matches delegate 'System.EventHandler' please help!

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  • how to remove ConcurrentModificationException

    - by maverick
    what is this exception and how to remove this in my problem i am creating an arraylist of objects, and after checking some condition,i want to remove some objects. but the program is giving this exception ConcurrentModificationException. how to remove this thanks in advance

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  • Should I ignore the occasional Invalid viewstate error?

    - by Richard Ev
    Every now and then (once every day or so) we're seeing the following types of errors in our logs for an ASP.NET 3.5 application Invalid viewstate Invalid postback or callback argument Are these something that "just happens" from time-to-time with an ASP.NET application? Would anyone recommend we spend a lot of time trying to diagnose what's causing the issues?

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  • How can I intercept an exception occurred during serialization in WCF?

    - by bonomo
    I have a legit data object with all data contract / data member attributes. For some reason the WCF service crashes after the operation has completed and the result is passed as a return value. I believe it has something to do with WCF not being able to serialize that result properly. The test client doesn't say anything specific: The underlying connection was closed: The connection was closed unexpectedly. Server stack trace: at System.ServiceModel.Channels.HttpChannelUtilities.ProcessGetResponseWebException(WebException webException, HttpWebRequest request, HttpAbortReason abortReason) at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout) at System.ServiceModel.Channels.RequestChannel.Request(Message message, TimeSpan timeout) at System.ServiceModel.Dispatcher.RequestChannelBinder.Request(Message message, TimeSpan timeout) at System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout) at System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation) at System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message) Exception rethrown at [0]: at System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg) at System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type) at IFacade.PickSecurities(String pattern, Int32 atMost) at FacadeClient.PickSecurities(String pattern, Int32 atMost) Inner Exception: The underlying connection was closed: The connection was closed unexpectedly. at System.Net.HttpWebRequest.GetResponse() at System.ServiceModel.Channels.HttpChannelFactory.HttpRequestChannel.HttpChannelRequest.WaitForReply(TimeSpan timeout) I am in control of creating the instance of the service using a customized service host factory. I know I can set up trace listeners and check the logs, but it's a lot of hassle to do. So I would rather handle it explicitly on the server at the time it happens. So I how can I intercept that exception programmatically and return an appropriate fault meassage?

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  • What should I do if a IOException is thrown?

    - by Roman
    I have the following 3 lines of the code: ServerSocket listeningSocket = new ServerSocket(earPort); Socket serverSideSocket = listeningSocket.accept(); BufferedReader in = new BufferedReader(new InputStreamReader(serverSideSocket.getInputStream())); The compiler complains about all of these 3 lines and its complain is the same for all 3 lines: unreported exception java.io.IOException; In more details, these exception are thrown by new ServerSocket, accept() and getInputStream(). I know I need to use try ... catch .... But for that I need to know what this exceptions mean in every particular case (how should I interpret them). When they happen? I mean, not in general, but in these 3 particular cases.

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  • C++ visitor pattern handling templated string types?

    - by Steve the Plant
    I'm trying to use the visitor pattern to serialize the contents of objects. However one snag I'm hitting is when I'm visiting strings. My strings are of a templated type, similar to STL's basic_string. So something like: basic_string<char_type, memory_allocator, other_possible_stuff> \\ many variations possible! Since I can have very many different templated string types, I can't go and add them to my visitor interface. It would be ridiculous. But I can't add templates to my VisitString method because C++ prevents using templates parameters in virtual methods. So what are my options to work around this?

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  • Server.TransferRequest returns blank page on specific server

    - by jishi
    I'm facing an issue that seems to be related to configuration. I have a webapplication based on MonoRail, where we utilize the routing feature from MonoRail. On the first request after the application has started, the routing isn't initialized. To circumvent this, I have the following code in Application_OnError(): public virtual void Application_OnError() { if ( // identified as routing error ) Server.TransferRequest( Context.Request.RawUrl, false ); return; } Problem beeing that on our development server (which runs server 2008 R2, with IIS 7.5 and .NET 3.5) returns a blank page without headers, but on my workstation (which runs win7, IIS 7.5 and .NET 3.5) it works fine. What could be the cause of this? If the code in Application_OnError() throws an exception, what would be the expected output? I have verified the following: The access-log shows one entry, I'm not sure if a TransferRequest would show up as a second entry when invoked successfully The application actually do some work according to my internal logs, and it doesn't die since a subsequent requests works flawlessly (because routing will be active) Any hints on what to look for would be greatly appreciated!

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  • iPhone: Error and error handling confusion in comparison.

    - by Mr. McPepperNuts
    NSArray *results = [managedObjectContext executeFetchRequest:request error:&error]; if(results == nil){ NSLog(@"No results found"); searchObj = nil; }else{ if ([[[results objectAtIndex:0] name] caseInsensitiveCompare:passdTextToSearchFor] == 0) { NSLog(@"results %@", [[results objectAtIndex:0] name]); searchObj = [results objectAtIndex:0]; }else { NSLog(@"No results found"); searchObj = nil; } } The code above compares data a user enters to data pulled from a database. If I enter data which is in the database; it works. But if I enter complete gibberish it returns the error below instead of "No results found." *** WebKit discarded an uncaught exception in the webView:shouldInsertText:replacingDOMRange:givenAction: delegate: <NSRangeException> *** -[NSCFArray objectAtIndex:]: index (0) beyond bounds (0) The results array being null should be accounted for during the checks in the above code, no?

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  • Event handling for a dynamically added user control

    - by francisf
    Hi, I have a user control say SearchVendor.ascx which contains 4 buttons a gridview and another user control. I need to load the control dynamically actually as a modal pop up I get this code VendorProductSearch uc = Page.LoadControl("~/Controls/Proposal/VendorProductSearch.ascx") as VendorProductSearch; uc.ShowVendorProductSearch(true); _tempPlaceHolder.Controls.Add(uc); it works fine the control gets loaded properly but onclick of any button the second time the control disappears ??? I want the dynamically added control to remain until the user clicks on the cancel button Any idea as to how to achive this ? Thanks & Regards, Francis P.

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  • EHsc vc EHa (synchronous vs asynchronous exception handling)

    - by watson1180
    Could you give a bullet list of practical differences/implication? I read relevant MSDN article, but my understanding asynchronous exceptions is still a bit hazy. I am writing a test suite using Boost.Test and my compiler emits a warning that EHa should be enabled: warning C4535: calling _set_se_translator() requires /EHa The project itself uses only plain exceptions (from STL) and doesn't need /EHa switch. Do I have to recompile it with /EHa switch to make the test suite work properly? My feeling is that I need /EHa for the test suit only. Thank you and happy new year.

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  • DUMP in unhandled C++ exception

    - by Jorge Vasquez
    In MSVC, how can I make any unhandled C++ exception (std::runtime_error, for instance) crash my release-compiled program so that it generates a dump with the full stack from the exception throw location? I have installed NTSD in the AeDebug registry an can generate good dumps for things like memory access violation, so the matter here comes down to crashing the program correctly, I suppose. Thanks in advance.

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  • Handling Application Logic in Multiple AsyncTask onPostExecute()s

    - by stormin986
    I have three simultaneous instances of an AsyncTask for download three files. When two particular ones finish, at the end of onPostExecute() I check a flag set by each, and if both are true, I call startActivity() for the next Activity. I am currently seeing the activity called twice, or something that resembles this type of behavior. Since the screen does that 'swipe left' kind of transition to the next activity, it sometimes does it twice (and when I hit back, it goes back to the same activity). It's obvious two versions of the activity that SHOULD only get called once are being put on the Activity stack. The only way I can find that this is possible is if both AsyncTasks' onPostExecute() executed SO simultaneously that they were virtually running the same lines at the same time, since I set the 'itemXdownloaded' flag to true right before I check for both and call startActivity(). But this is happening enough that it's very hard for me to believe that both downloads are finishing precisely at the same time and having their onPostExecute()s so close together... Any thoughts on what could be going on here? General gist of code (details removed, ignore any syntactical errors I may have edited in): // In onPostExecute() switch (downloadID) { case DL1: dl1complete = true; break; case DL2: dl2complete = true; break; case DL3: dl3complete = true; break; } // If 1 and 2 are done, move on (DL3 still going in background) if ( downloadID != DL3 && dl1complete && dl2complete) { ParentClass.this.startActivity(new Intent(ParentClass.this, NextActivity.class)); }

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  • Communication between layers in an application

    - by Petar Minchev
    Hi guys! Let's assume we have the following method in the business layer. What's the best practice to tell the UI layer that something went wrong and give also the error message? Should the method return an empty String when it was OK, otherwise the error message, or should it throw another exception in the catch code wrapping the caught exception? If we choose the second variant then the UI should have another try,catch which is too much try,catch maybe. Here is a pseudocode for the first variant. public String updateSomething() { try { //Begin transaction here dataLayer.do1(); dataLayer.do2(); dataLayer.doN(); } catch(Exception exc) { //Rollback transaction code here return exc.message; } return ""; } Is this a good practice or should I throw another exception in the catch(then the method will be void)?

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  • Is it safe to silently catch ClassCastException when searching for a specific value?

    - by finnw
    Suppose I am implementing a sorted collection (simple example - a Set based on a sorted array.) Consider this (incomplete) implementation: import java.util.*; public class SortedArraySet<E> extends AbstractSet<E> { @SuppressWarnings("unchecked") public SortedArraySet(Collection<E> source, Comparator<E> comparator) { this.comparator = (Comparator<Object>) comparator; this.array = source.toArray(); Collections.sort(Arrays.asList(array), this.comparator); } @Override public boolean contains(Object key) { return Collections.binarySearch(Arrays.asList(array), key, comparator) >= 0; } private final Object[] array; private final Comparator<Object> comparator; } Now let's create a set of integers Set<Integer> s = new SortedArraySet<Integer>(Arrays.asList(1, 2, 3), null); And test whether it contains some specific values: System.out.println(s.contains(2)); System.out.println(s.contains(42)); System.out.println(s.contains("42")); The third line above will throw a ClassCastException. Not what I want. I would prefer it to return false (as HashSet does.) I can get this behaviour by catching the exception and returning false: @Override public boolean contains(Object key) { try { return Collections.binarySearch(Arrays.asList(array), key, comparator) >= 0; } catch (ClassCastException e) { return false; } } Assuming the source collection is correctly typed, what could go wrong if I do this?

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  • ASP.NET: How can I properly redirect requests with 404 errors?

    - by Adrian Grigore
    Hi, I'd like my ASP.NET MVC application to redirect failed requests to matching action methods of a certain controller. This works fine on my development machine running Windows 7, but not on my production machine running Windows 2008 R2. I set up my web.config as follows: <customErrors mode="On" defaultRedirect="/Error/ServerError/500"> <error statusCode="403" redirect="/Error/AccessDenied" /> <error statusCode="404" redirect="/Error/FileNotFound" /> </customErrors> This customErrors section works fine on both of my machines (production and development) for 500 Internal Server errors. It also works fine for 404 errors on my development machine. However, it does not properly redirect 404 errors on the production machine. Instead of /Error/FileNotFound, I get the standard 404 page that comes with IIS 7. What could be the problem here?

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  • Error debugging - Conversion from String to Double

    - by Jamie Taylor
    I'm doing some error debugging trying to get the errors on our website down to a minimum and there seems to be an error that is popping up quite a lot Conversion from string "" to type 'Double' is not valid. I'm unable to replicate this problem but I can see that it is happening. I've been looking through the code in one of the pages and strolled across this Dim varWeek As String If varWeek < 10 Then 'Do something' End If Could this be causing the problem as it is trying to see if a String is less than 10 which is an Integer? As I said before as I am unable to see this error in the first place so changing this to an Integer doesn't change anything on my system. Thanks.

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