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  • C# Event Handlers automatically created by WinForms Designer

    - by RHaguiuda
    Just moved from VB.NET to C#. In VB to connect and Event Handler to a Sub we use the Handles clause. From what it seems, this do not exist in C#. After creating a simple application with a button I realize that Window Forms Designer automatically created an EventHandler to my button1_Click function (after I double clicked it), in Form1.Designer.cs with this code: this.button1.Click += new System.EventHandler(this.button1_Click); But, in VB, the WinForms Designer create the Handles clause in my class, in the function header. So, C# create the default EventHandler in designer file, while VB creates in main class with control resides. Is this correct? Am I missing something here?

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  • How to roll back changes in gridview in case of incorrect input

    - by Mustafa A. Jabbar
    Hi, I have a DataGridView that is bound to a list of object. It has some columns that the user can edit. There are certain inputs that are not allowed for a row as a whole. How can I roll back if the user enters invalid inputs in some cell. I tried using the RowValidating event handler but it was not called after cell value has been changed. Even when I implemet CellValueChanged, I still cannot roll back the changes. Any idea how to accomplish this

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  • File IO, Handling CRLF

    - by aCuria
    Hi, i am writing a program that takes a file and splits it up into multiple small files of a user specified size, then join the multiple small files back again. 1) the code must work for c, c++ 2) i am compiling with multiple compilers. I am reading and writing to the files by using the stl functions fread() and fwrite() The problem I am having pertains to CRLF. If the file I am reading from contains CRLF, then I want to retain it when i split and join the files back together. If the file contains LF, then i want to retain LF. Unfortunately, fread() seems to store CRLF as \n (I think), and whatever is written by fwrite() is compiler-dependent. How do i approach this problem? Thanks.

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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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  • Where is this exception caught and handled?

    - by Zaki
    In some code I've been reading, I've come across this : class Someclass { public static void main(String[] args) throws IOException { //all other code here...... } } If main() throws an exception, in this case its an IOException, where is it caught and handled?

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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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  • When is it appropriate to use C++ exceptions?

    - by krebstar
    I'm trying to design a class that needs to dynamically allocate some memory.. I had planned to allocate the memory it needs during construction, but how do I handle failed memory allocations? Should I throw an exception? I read somewhere that exceptions should only be used for "exceptional" cases, and running out of memory doesn't seem like an exceptional case to me.. Should I allocate memory in a separate initialization routine instead and check for failures and then destroy the class instance gracefully? Or should I use exceptions instead? The class won't have anything useful to do if these memory allocations should fail.. EDIT: The consensus seems to be that running out of memory IS an exceptional case. Will see how to go about this.. Thanks.. :)

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  • Exception handling in Linq to SQL for customers without orders

    - by stackoverflowuser
    I have the following code to retrieve customer name, total (orders ), sum (order details) for reach customer in Northwind database. The problem with below code is that it raises an exception since a few customers dont have any entry in orders table. I know using the query syntax (join) the exception can be avoided. I want to know if the same can be handled with the extension method syntax. var customerOrders = db.Customers .Select(c => new { CompanyName = c.CompanyName, TotalOrders = c.Orders.Count(), TotalQuantity = c.Orders .SelectMany(o => o.Order_Details).Sum(o=>o.Quantity) });

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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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  • 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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  • Why use event listeners over function calls?

    - by Organiccat
    I've been studying event listeners lately and I think I've finally gotten them down. Basically, they are functions that are called on another object's method. My question is, why create an event listener when calling the function will work just fine? Example, I want to call player.display_health(), and when this is fired, the method player.get_health() should be fired and stored so that display_health() has access to it. Why should I use an event listener over simply calling the function? Even if display_health() were in another object, this still doesn't appear to be a problem to me. If you have another example that fits the usage better, please let me know. Perhaps particular languages don't benefit from it as much? (Javascript, PHP, ASP?)

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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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  • Keyboard- and mouse-event transparent widget

    - by Gajender
    When i click a button my main window i want it to become transparent to keyboard and mouse events, i.e. all keyboard and mouse events should pass to any windows below it as if that window is not present there. "Qt::WA_TransparentForMouseEvents" does not work here as this only make child windows transparent to keyboard and mouse events i guess. And my window is main window and i want to pass all event to any window on desktop not just parent window.

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  • How should I re-raise a Delphi exception after logging it?

    - by Nik
    Do you know a way to trap, log, and re-raise exception in Delphi code? A simple example: procedure TForm3.Button1Click(Sender: TObject); begin try raise Exception.Create('Bum'); except on E: Exception do begin MyHandleException(E); end; end; end; procedure TForm3.MyHandleException(AException: Exception); begin ShowMessage(AException.Message); LogThis(AException.Message); // raise AException; - this will access violate end; So I need to re-raise it in the except block but I was wondering if there is a better way to write my own method to handle and (on specific conditions) to re-raise exceptions.

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  • performing a javascript event without triggering that event handler

    - by bento
    In my latest code, I have an event handler for a focus on a textarea. When the user clicks on the textarea, that event-handler is triggered which sets some other DOM states based on the selected textarea. However, elsewhere in my program I want to programmatically set the focus of the textarea without triggering that event handler. I know Backbone, for instance, has a way to silently perform an action. My only pseudo-solution is to temporarily set a variable: var silence = true; And then, in my event handler, only perform the logic if silence is false. The handler is still triggered, but the logic doesn't run. Does anyone else know of better strategies for this?

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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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  • Capture and handling the tab/Textchanged event in a textbox in asp.net MVC

    - by Icerman
    I have the following code th handle a user name validation on the server side. But the event seems not firing since break points in js or C# code didn't hit. Can anyone point out where I did wrong? Here is the user control which has a user name textbox: <%: Html.TextBox("UserName", Model.Username, new { maxlength = "40", size = "20", tabindex = "1", @onchange = "CheckAvailability()" })% CheckAvailability() is defined in the User.Validation.js and included in the above user control: $(document).ready(function () { function CheckAvailability() { $.post("/Home/Survey/CheckAvailability", { Username: $("#UserName").val() }, function (data) { var myObject = eval('(' + data + ')'); var newid = myObject; if (newid == 0) { $("#usernamelookupresult").html("<font color='green'>Available :-D</font>") } else { $("#usernamelookupresult").html("<font color='red'>Taken :-(</font>") } }); } }); Here is the survey controller function which will have server side validation: [HttpPost] public ActionResult CheckAvailability(string Username) { int Taken = 0; // This is where you add your database lookup if (Username == "abc") { Taken = 1; } return Json(Taken); }

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  • Catching specific vs. generic exceptions in c#

    - by Scott Vercuski
    This question comes from a code analysis run against an object I've created. The analysis says that I should catch a more specific exception type than just the basic Exception. Do you find yourself using just catching the generic Exception or attempting to catch a specific Exception and defaulting to a generic Exception using multiple catch blocks? One of the code chunks in question is below: internal static bool ClearFlags(string connectionString, Guid ID) { bool returnValue = false; SqlConnection dbEngine = new SqlConnection(connectionString); SqlCommand dbCmd = new SqlCommand("ClearFlags", dbEngine); SqlDataAdapter dataAdapter = new SqlDataAdapter(dbCmd); dbCmd.CommandType = CommandType.StoredProcedure; try { dbCmd.Parameters.AddWithValue("@ID", ID.ToString()); dbEngine.Open(); dbCmd.ExecuteNonQuery(); dbEngine.Close(); returnValue = true; } catch (Exception ex) { ErrorHandler(ex); } return returnValue; } Thank you for your advice EDIT: Here is the warning from the code analysis Warning 351 CA1031 : Microsoft.Design : Modify 'ClearFlags(string, Guid)' to catch a more specific exception than 'Exception' or rethrow the exception

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  • Reverse massive text file in Java

    - by DanJanson
    What would be the best approach to reverse a large text file that is uploaded asynchronously to a servlet that reverses this file in a scalable and efficient way? text file can be massive (gigabytes long) can assume mulitple server/clustered environment to do this in a distributed manner. open source libraries are encouraged to consider I was thinking of using Java NIO to treat file as an array on disk (so that I don't have to treat the file as a string buffer in memory). Also, I am thinking of using MapReduce to break up the file and process it in separate machines. Any input is appreciated. Thanks. Daniel

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  • wxPython: How to handle event binding and Show() properly.

    - by Gopal
    Hi all, I'm just starting out with wxPython and this is what I would like to do: a) Show a Frame (with Panel inside it) and a button on that panel. b) When I press the button, a dialog box pops up (where I can select from a choice). c) When I press ok on dialog box, the dialog box should disappear (destroyed), but the original Frame+Panel+button are still there. d) If I press that button again, the dialog box will reappear. My code is given below. Unfortunately, I get the reverse effect. That is, a) The Selection-Dialog box shows up first (i.e., without clicking on any button since the TopLevelframe+button is never shown). b) When I click ok on dialog box, then the frame with button appears. c) Clicking on button again has no effect (i.e., dialog box does not show up again). What am I doing wrong ? It seems that as soon as the frame is initialized (even before the .Show() is called), the dialog box is initialized and shown automatically. I am doing this using Eclipse+Pydev on WindowsXP with Python 2.6 ============File:MainFile.py=============== import wx import MyDialog #This is implemented in another file: MyDialog.py class TopLevelFrame(wx.Frame): def __init__(self,parent,id): wx.Frame.__init__(self,parent,id,"Test",size=(300,200)) panel=wx.Panel(self) button=wx.Button(panel, label='Show Dialog', pos=(130,20), size=(60,20)) # Bind EVENTS --> HANDLERS. button.Bind(wx.EVT_BUTTON, MyDialog.start(self)) # Run the main loop to start program. if __name__=='__main__': app=wx.PySimpleApp() TopLevelFrame(parent=None, id=-1).Show() app.MainLoop() ============File:MyDialog.py=============== import wx def start(parent): inputbox = wx.SingleChoiceDialog(None,'Choose Fruit', 'Selection Title', ['apple','banana','orange','papaya']) if inputbox.ShowModal()==wx.ID_OK: answer = inputbox.GetStringSelection() inputbox.Destroy()

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  • Handling input from a keyboard wedge

    - by JDibble
    Following on from the question asked by Mykroft Best way to handle input from a keyboard “wedge” http://stackoverflow.com/questions/42437/best-way-to-handle-input-from-a-keyboard-wedge. I need to write a class that intercepts key strokes, if the input is determined to be from the keyboard wedge (as described in the above post) the data will be directed to POS classes to handle, otherwise they keystrokes must be passed on to be handled in windows in the normal manner. This raises two questions How can I intercept key strokes when not in a WinForm. How can I pass on the keypresses to windows. Thanks JDibble

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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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  • Capture KeyUp event on form when child control has focus

    - by Jon B
    I need to capture the KeyUp event in my form (to toggle a "full screen mode"). Here's what I'm doing: protected override void OnKeyUp(KeyEventArgs e) { base.OnKeyUp(e); if (e.KeyCode == Keys.F12) this.ToggleFullScreen(); } private void ToggleFullScreen() { // Snazzy code goes here } This works fine, unless a control on the form has focus. In that case, I don't get the event at all (also tried OnKeyDown - no luck there either). I could handle the KeyUp event from the child control, but the controls on the form are generated dynamically, and there may be many of them - each having many children of their own. Is there any way to do this without generating event handlers for every control on the screen (which I certainly could do with a recursive function)?

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