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• PropertyChanged doesn't work properly

  - by Karen

  Hello, I have a Silverlight application in which I implemented MVVM pattern. In my application there is a child window on which I have ComboBox. I bound ItemsSource and SelectedItem of my combobox to a property (typeof ObservableCollection) and property of MyType appropriately. MyType is a "MODEL" derived from INotifyPropertyChanged. When my window is loaded I set values to this properties. But my combobox doesn't display selected item. I found that when I set property which is bound to selected item (in ViewModel), the PropertyChanged event is null. Can anyone help me. Thanks.

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• What's the difference between the 'DES' class and The 'DESCryptoServiceProvider' class?

  - by IbrarMumtaz

  All I can make out is that one of them is the BC for all 'DES' algorithms to be derived from and the later is a wrapper for the Cryptographic service provider implementation of the DES algorithm. The reason why I ask is that I am going over .Net Security and the MS official training book simply refers to the DES class but the another official MS book refers to the DESCrypto' class. What's the difference between these two? When would you use either of them? What do I need to know as far as the 70-536 exam is concerned. I am asking my question from an educational P.O.V as far as the 70-536 exam is concerned. Thanks In Advance. Ibrar

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• What does: throw 0 do/mean? Is it "bad"?

  - by MartinP

  Context I came across some code, like this: if( Some_Condition ) throw 0; I googled a bit, and found a few other code snippets using that odd looking throw 0 form. I presume one would catch this as: catch(const int& e) { } Or is this a NULL ptr? to be caught as void* ? Question What does this throw 0 do? Is it special in some way? My normal preference would be to throw something that is (or derived from) std::exception. So to me this looks "bad". Is it "bad" ?

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• iPhone+Quartz+OpenGL. What is the correct way for Quartz and OpenGL to play nice together regarding

  - by dugla

  So we know the CoreGraphics/Quartz imaging model is based on pre-multiplied alpha. We also know that OpenGL blending is based on un-premultiplied alpha. What is the best practice to avoid head explosion when doing blending with textures that are derived from pre-multiplied alpha imagery (PNG files generated in Photoshop with pre-multiplied alpha). Given the apples/oranges mish mash of Quartz and OpenGL, what is the correct glBlendFunc for doing the fundamental Porter/Duff "over" operation? Typical example: A simple paint program. Brush shapes are texture-map patterns created from pre-multiplied alpha rgba images. Paint color is specified via glColor4(...) with the alpha channel used to control paint transparency. GL_MODULATE is used so the brush texture multiplies the (translucent) paint color to blend the color into the canvas. Problem: The texture is premult. The color is not. What is the correct way to handle this fundamental inconsistency? Thanks, Doug

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• overriding protected internal with protected!

  - by Asad Butt

  This is an extension for this question asked an hour ago. We cannot modify the access modifiers, when overriding a virtual method in derived class. Consider Control class in System.Web.UI namespace public class Control : IComponent, IDisposable,... { protected internal virtual void CreateChildControls() { } . . } Now Consider This public class someClass : System.Web.UI.Control { // This should not compile but it does protected override void CreateChildControls() { } // This should compile but it does not protected internal override void CreateChildControls() { } } can any body explain this ? Thanks

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• Setting multiple datasource for a report in Asp.net

  - by Nandini

  Hi all, I have a report whose data is derived from two stored procedures.so i need to set these two datasources for generating the report.But the reports which have only one SP, ie.only one datasource works properly. For setting the datasource, i wrote code like this: dim reportdocument as ReportDocument Dim reportPath As String = Server.MapPath("CrystalRpts\Report.rpt") ReportDocument.Load(reportPath) 'Function for Setting the Connection SetDBLogonForReport(MyConnectionInfo, ReportDocument) dim dt1 as datatable=Datasource1 dim dt2 as datatable=Datasource2 dt1.merge(dt2) reportdocument.setDataSource(dt1) CrystalReportViewer.ReportSource=reportdocument But, the report is not generating.it shows the following error The Report requires additional information Servername:- Server Database:- Database UserID:- Password:- But the reports which have only one SP, ie.only one datasource works properly.What colud be reason for this error?

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• Sizing of a UITableViewCell

  - by Xetius

  I have created a UITableViewCell derived class which resizes itself to display at an indentation level. I have tried setting indentationLevel and indentationWidth using the following in the ViewControllers cellForRowAtIndexPath: cell.indentationLevel = [[item objectForKey:@"indent"] intValue]; cell.indentationWidth = CELL_INDENT_SIZE; This in itself does not indent the cell, so I am using the following layoutSubviews in the UITableViewCell: -(void)layoutSubviews { CGFloat indentSize = (self.indentationLevel - 1) * self.indentationWidth; CGRect r = containerView.frame; containerView.frame = CGRectMake (r.origin.x + indentSize, r.origin.y, r.size.width - indentSize, r.size.height); DLog(@"frameRect : %f, %f, %f, %f, %f",indentSize, r.origin.x, r.origin.y, r.size.width, r.size.height); [super layoutSubviews]; } This works fine for the initial layout, but when the cell is selected, it recalculates itself from the new dimensions and effectively shrinks the cell every time it is selected. How can I resize this cell so that it doesn't keep changing the layout.

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• Can a DataTemplate be a Page?

  - by dthrasher

  I'm using the MVVM pattern to create a WPF standalone application. My program compiles in Visual Studio 2008, but I frequently get warnings in the editor for my DataTemplates. In my MainWindow.xaml, I've defined the following DataTemplate: <DataTemplate DataType="{x:Type ViewModels:TagViewModel}"> <Views:TagView /> </DataTemplate> Where "TagView" is derived from a Page, rather than an ordinary UserControl. This causes the following message to appear every time I reload the designer in Visual Studio: "Could not create an instance of type 'TagView'. Yet the solution compiles fine and the program seems to work properly. Is this a bug in the Visual Studio 2008 editor? Or am I doing something wrong?

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• Migrating C# code from Cassandra .5 to .6

  - by Jonathan

  I have some some simple code derived from an example that is meant to form a quick write to the Cassandra db, then loop back and read all current entries, everything worked fine. When .6 came out, i upgraded Cassandra and thrift, which threw errors in my code (www[dot]copypastecode[dot]com/26760/) - i was able to iron out the errors by converting the necessary types, however in the version that compiles now only seems to read one item back, im not sure if its not saving db changes or if its only reading back 1 entry. the "fixed" code is here: http://www.copypastecode.com/26752/. Any help would be greatly appreciated.

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• ACL suggestions needed for a small light framework developed

  - by Sai

  Hello all, I've developed a small framework that was needed for the firm that I work. The problem is I've not made a full level framework, as developers are finding tough time to understand what is what, So I made a simple structure with app/controllers, app/models, app/views so that they can clearly separate the code and can get used to higher frameworks later. All other things like components/modules/helpers are just coded for now in a file called app_functions.php. The above framework is derived from cakePHP, not all, but just the framework uses a modified code of dispatcher of cake. The models all work with normal sqls, and views with pure html using a template engine. Now I'm trying to develop a small application over it, it cameout well, but ACL is something which many versions of it have not proved that satisfactory. Can anybody suggest a good ACL. I've checked phpGACL(too heavy), Zend_ACL likely won't be compatible, Cakephp's ACL which wont fit in the structure,as we are not using cake's SQLs, as there too many queries hitting the database for one page display.

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• Flex 3: Possible to add a Context Menu to a ItemRenderer inside a DataGrid?

  - by gmoniey

  I have an ItemRenderer that is shared by several applications (inside a DataGrid), and I would like to add a context menu to it (rather than in each application). The renderer is derived from the Canvas class, and the code to create the context menu looks something like: var menuItem:ContextMenuItem = new ContextMenuItem("Test"); menuItem.addEventListener(ContextMenuEvent.MENU_ITEM_SELECT, contextCallback); var customContextMenu:ContextMenu = new ContextMenu(); customContextMenu.hideBuiltInItems(); //hide flash menu customContextMenu.customItems.push(menuItem); this.contextMenu = customContextMenu; However, when I right click on the cell in the datagrid, I get the default Flash Context Menu. Is this not possible?

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• Can i override an abstract method written in a parent class, with a different name in a child class?

  - by Ranhiru

  abstract class SettingSaver { public abstract void add(string Name, string Value); public abstract void remove(string SettingName); } class XMLSettings : SettingSaver { public override void add(string Name, string Value) { throw new NotImplementedException(); } public override void remove(string SettingName) { throw new NotImplementedException(); } } Is there anyway that I can change the name of the add function in XMLSettings class to addSetting but make sure it overrides the add function in the SettingSaver? I know it should be definitely overridden in derived classes but just want to know whether I can use a different name :) Thanx in advance :D

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• Can the get of a property be abstract and the set be virtual?

  - by K. Georgiev

  I have a base class like this: public class Trajectory{ public int Count { get; set; } public double Initial { get; set { Count = 1; } } public double Current { get; set { Count ++ ; } } } So, I have code in the base class, which makes the set-s virtual, but the get-s must stay abstract. So I need something like this: ... public double Initial { abstract get; virtual set { Count = 1; } } ... But this code gives an error. The whole point is to implement the counter functionality in the base class instead in all the derived classes. So, how can I make the get and set of a property with different modifiers?

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• [C++]Advantage of using a static member function instead of an equivalent non-static member function

  - by jonathanasdf

  I was wondering whether there's any advantages to using a static member function when there is a non-static equivalent. Will it result in faster execution (because of not having to care about all of the member variables), or maybe less use of memory (because of not being included in all instances)? Basically, the function I'm looking at is an utility function to rotate an integer array representing pixel colours an arbitrary number of degrees around an arbitrary centre point. It is placed in my abstract Bullet base class, since only the bullets will be using it and I didn't want the overhead of calling it in some utility class. It's a bit too long and used in every single derived bullet class, making it probably not a good idea to inline. How would you suggest I define this function? As a static member function of Bullet, of a non-static member function of Bullet, or maybe not as a member of Bullet but defined outside of the class in Bullet.h? What are the advantages and disadvantages of each?

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• QT drawing without erasing widget

  - by faya

  Hello, If I have a derived object of QWidget class and on slot function in it I have an update(). here is some pseudocode: *.h slot: updateNow(); *.cpp constructor() { setPalllete(QPallete(QColor(250,250,200))); setAUtoFillBackground(true); } updateNow() { update(); } paintEvent() { QPainter painter(this); painter.drawRect(1,2,3,4); } So how should I don't get erased my pallete after update() call? P.S. - Sorry for my English and only pseudocode.

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• Unresolved symbol when inheriting interface

  - by LeopardSkinPillBoxHat

  It's late at night here and I'm going crazy trying to solve a linker error. If I have the following abstract interface: class IArpPacketBuilder { public: IArpPacketBuilder(const DslPortId& aPortId); virtual ~IArpPacketBuilder(); // Other abstract (pure virtual methods) here... }; and I instantiate it like this: class DummyArpPacketBuilder : public IArpPacketBuilder { public: DummyArpPacketBuilder(const DslPortId& aPortId) : IArpPacketBuilder(aPortId) {} ~DummyArpPacketBuilder() {} }; why am I getting the following error when linking? Unresolved symbol references: IArpPacketBuilder::IArpPacketBuilder(DslPortId const&): ppc603_vxworks/_arpPacketQueue.o IArpPacketBuilder::~IArpPacketBuilder(): ppc603_vxworks/_arpPacketQueue.o typeinfo for IArpPacketBuilder: ppc603_vxworks/_arpPacketQueue.o *** Error code 1 IArpPacketBuilder is an abstract interface, so as long as I define the constructors and destructions in the concrete (derived) interface, I should be fine, no? Well it appears not.

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• Is the MySQL FOSS License Exception transitive - does it remove the GPL restrictions for downstream

  - by Eric

  I'm looking at building a MySQL client plugin for a proprietary product, which would violate the GPL as discussed in the FAQ at http://www.gnu.org/licenses/gpl-faq.html#NFUseGPLPlugins However, according to the MySQL FOSS License Exception ("FLE"), discussed at http://www.mysql.com/about/legal/licensing/foss-exception/, you can license an open-source product built with the client with many alternatives. The oursql library (https://launchpad.net/oursql) is BSD-licensed. Is this a valid way around the GPL? By my reading of the FLE, the only clause that refers to downstream uses of derived works is section 2.e: All works that are aggregated with the Program or the Derivative Work on a medium or volume of storage are not derivative works of the Program, Derivative Work or FOSS Application, and must reasonably be considered independent and separate works. This is the case for our product: it is not a derivative work of oursql, and in fact accesses it only via a plugin-driven interface. So is this a valid loophole?

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• Why is this if statement failing?

  - by Rawling

  I'm working on an existing class that is two steps derived from System.Windows.Forms.Combo box. The class overrides the Text property thus: public override string Text { get { return this.AccessibilityObject.Value; } set { if (base.Text != value) { base.Text = value; } } } The reason given for that "get" is this MS bug: http://support.microsoft.com/kb/814346 However, I'm more interested in the fact that the "if" doesn't work. There are times where "base.Text != value" is true and yet pressing F10 steps straight to the closing } of the "set" and the Text property is not changed. I've seen this both by just checking values in the debugger, and putting a conditional breakpoint on that only breaks when the "if" statement's predicate is true. How on earth can "if" go wrong? The class between this and ComboBox doesn't touch the Text property. The bug above shouldn't really be affecting anything - it says it's fixed in VS2005. Is the debugger showing different values than the program itself sees?

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• jQuery Ajax post with dynamic url

  - by morpheous

  I want to send an AJAX POST, but I want the url that the data is sent to, to be derived from the id of the element that was clicked. This is what I have so far: I have written a javascript function (get_my_url) that returns a url, depending on the element id that was passed to the function. The problem is, it is not clear how to bind the function (get_my_url) to the url param of the .ajax() method. jQuery('.elem1').click(function(){ jQuery.ajax({ async: false, type: 'POST', url: get_my_url(jQuery(this).attr('id')), data: 'id1=1', dataType: 'json', success: function(data){ msg = data.msg }, error: function(xrq, status, et){msg='Oops. An error occured!'} }); Does anyone know how to pass a function to the url param?

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• Compiler doesn't find methods from base class

  - by Paul

  I am having a problem with my virtual methods in a derived class. Here are my (simplified) C++ classes. class Base virtual method accept( MyVisitor1* v ) { /*implementation is here*/ }; virtual method accept( MyVisitor2* v ) { /*implementation is here*/ }; virtual method accept( MyVisitor3* v ) { /*implementation is here*/ }; class DerivedClass virtual method accept( MyVisitor2* v ) { /*implementation is here*/ }; The following use causes VS 2005 to give: "error C2664: 'DerivedClass::accept' : cannot convert parameter 1 from 'Visitor1*' to 'Visitor2 *'". DerivedClass c; MyVisitor1 v1; c.accept(v1); I was expecting the compiler to find and call Base::accept(MyVisitor1) for my DerivedClass as well. Obviously this is not working, but I don't understand why. Any ideas? Thanks, Paul

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• unique_ptr boost equivalent?

  - by wowus

  Is there some equivalent class for C++1x's std::unique_ptr in the boost libraries? The behavior I'm looking for is being able to have an exception-safe factory function, like so... std::unique_ptr<Base> create_base() { return std::unique_ptr<Base>(new Derived); } void some_other_function() { std::unique_ptr<Base> b = create_base(); // Do some stuff with b that may or may not throw an exception... // Now b is destructed automagically. }

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• Can you figure out the password hashing scheme?

  - by Adal

  I have two passwords and two resulting hashes. I can't figure out how the hash is derived from the password. I don't know if salting is used. I don't know if the password is hashed as a integer value or as a string (possibly Unicode). Password: 6770 Hash: c12114b91a3841c143bbeb121693e80b Password: 9591 Hash: 25238d578b6a61c2c54bfe55742984c1 The hash length seems to suggest MD5. Anybody has any ideas what I could try? Note: This is not for hacking purposes. I'm trying to access a service through an API instead of it's desktop client, and I can't figure out how to compute the password hash. Currently instead of using my real password I'm sending directly the hash.

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• abstract method signature, inheritance, and "Do" naming convention

  - by T. Webster

  I'm learning about design patterns and in examples of code I've seen a convention where the abstract class declares a method, for example: public abstract class ServiceBase { ... public virtual object GetSomething(); and then protected abstract object DoGetSomething(); My question is on why these two methods exist, since they appear to serve the same purpose. Is this so that the base class GetSomething() method logic cannot be overridden by inherited classes? But then again, the method is marked virtual, so it can be overridden anyway. What is the usefulness here in requiring derived class implementers to implement the abstract method when the virtual method can be called anyway?

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• Custom dropdown for CComboBox

  - by WalderFrey

  I'm trying to create a custom dropdown for a derivative of CComboBox. The dropdown will be a calendar control plus some 'hotspots', e.g. So I figure the best way to achieve this is to have a simple CWnd-derived class which acts as the parent to the calendar control, and have it paint the hotspots itself. The window needs to be a popup window - I think - rather than a child window so that it isn't clipped. But doing this causes the dialog (on which the combobox control is placed) to stop being the topmost (foreground?) window, leading to its frame being drawn differently: This spoils the illusion that the dropdown is part of the combobox since its acting more like a modal dialog at this point. Any suggestions on how I make the custom dropdown behave like the regular dropdown? Are there any other pitfalls I need to watch out for, e.g. focus and mouse capture issues?

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• Relevance of 'public' constructor in abstract class.

  - by Amby

  Is there any relevance of a 'public' constructor in an abstract class? I can not think of any possible way to use it, in that case shouldn't it be treated as error by compiler (C#, not sure if other languages allow that). Sample Code: internal abstract class Vehicle { public Vehicle() { } } The C# compiler allows this code to compile, while there is no way i can call this contructor from the outside world. It can be called from derived classes only. So shouldn't it allow 'protected' and 'private' modifiers only. Please comment.

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