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• Design pattern for isomorphic trees

  - by Peregring-lk

  I want to create a data structure to work with isomorphic tree. I don't search for a "algorithms" or methods to check if two or more trees are isomorphic each other. Just to create various trees with the same structure. Example: 2 - - - - - - - 'a' - - - - - - - 3.5 / \ / \ / \ 3 3 'f' 'y' 1.0 3.1 / \ / \ / \ 4 7 'e' 'f' 2.3 7.7 The first "layer" or tree is the "natural tree" (a tree with natural numbers), the second layer is the "character tree" and the third one is the "float tree". The data structure has a method or iterator to traverse the tree and to make diferent operations with its values. These operations could change the value of nodes, but never its structure (first I create the structure and then I configure the tree with its diferent layers). In case of that I add a new node, this would be applied to each layer. Which known design pattern fits with this description or is related with it?

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• Design for a plugin based application

  - by Varun Naik

  I am working on application, details of which I cannot discuss here. We have core framework and the rest is designed as plug in. In the core framework we have a domain object. This domain object is updated by the plugins. I have defined an interface in which I have function as DomainObject doProcessing(DomainObject object) My intention here is I pass the domain object, the plug in will update it and return it. This updated object is then passed again to different plugin to be updated. I am not sure if this is a good approach. I don't like passing the DomainObject to plugin. Is there a better way I can achieve this? Should I just request data from plugin and update the domain object myself?

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• DDD: Service or Repository

  - by tikhop

  I am developing an app in DDD manner. And I have a little problem with it. I have a Fare (airline fare) and FareRepository objects. And at some point I should load additional fare information and set this information to existing Fare. I guess that I need to create an Application Service (FareAdditionalInformationService) that will deal with obtaining data from the server and than update existing Fare. However, some people said me that it is necessary to use FareRepository for this problem. I don't know wich place is better for my problem Service or Repository.

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• Given the presentation model pattern, is the view, presentation model, or model responsible for adding child views to an existing view at runtime?

  - by Ryan Taylor

  I am building a Flex 4 based application using the presentation model design pattern. This application will have several different components to it as shown in the image below. The MainView and DashboardView will always be visible and they each have corresponding presentation models and models as necessary. These views are easily created by declaring their MXML in the application root. <s:HGroup width="100%" height="100%"> <MainView width="75% height="100%"/> <DashboardView width="25%" height="100%"/> </s:HGroup> There will also be many WidgetViewN views that can be added to the DashboardView by the user at runtime through a simple drop down list. This will need to be accomplished via ActionScript. The drop down list should always show what WidgetViewN has already been added to the DashboardView. Therefore some state about which WidgetViewN's have been created needs to be stored. Since the list of available WidgetViewN and which ones are added to the DashboardView also need to be accessible from other components in the system I think this needs to be stored in a Model object. My understanding of the presentation model design pattern is that the view is very lean. It contains as close to zero logic as is practical. The view communicates/binds to the presentation model which contains all the necessary view logic. The presentation model is effectively an abstract representation of the view which supports low coupling and eases testability. The presentation model may have one or more models injected in in order to display the necessary information. The models themselves contain no view logic whatsoever. So I have a several questions around this design. Who should be responsible for creating the WidgetViewN components and adding these to the DashboardView? Is this the responsibility of the DashboardView, DashboardPresentationModel, DashboardModel or something else entirely? It seems like the DashboardPresentationModel would be responsible for creating/adding/removing any child views from it's display but how do you do this without passing in the DashboardView to the DashboardPresentationModel? The list of available and visible WidgetViewN components needs to be accessible to a few other components as well. Is it okay for a reference to a WidgetViewN to be stored/referenced in a model? Are there any good examples of the presentation model pattern online in Flex that also include creating child views at runtime?

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• Advantages of Singleton Class over Static Class?

  Point 1)Singleton We can get the object of singleton and then pass to other methods.Static Class We can not pass static class to other methods as we pass objectsPoint 2) Singleton In future, it is easy to change the logic of of creating objects to some pooling mechanism. Static Class Very difficult to implement some pooling logic in case of static class. We would need to make that class as non-static and then make all the methods non-static methods, So entire your code needs to be changed.Point3:) Singleton Can Singletone class be inherited to subclass? Singleton class does not say any restriction of Inheritence. So we should be able to do this as long as subclass is also inheritence.There's nothing fundamentally wrong with subclassing a class that is intended to be a singleton. There are many reasons you might want to do it. and there are many ways to accomplish it. It depends on language you use.Static Class We can not inherit Static class to another Static class in C#. Think about it this way: you access static members via type name, like this: MyStaticType.MyStaticMember(); Were you to inherit from that class, you would have to access it via the new type name: MyNewType.MyStaticMember(); Thus, the new item bears no relationships to the original when used in code. There would be no way to take advantage of any inheritance relationship for things like polymorphism. span.fullpost {display:none;}

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• What are the consequences of immutable classes with references to mutable classes?

  - by glenviewjeff

  I've recently begun adopting the best practice of designing my classes to be immutable per Effective Java [Bloch2008]. I have a series of interrelated questions about degrees of mutability and their consequences. I have run into situations where a (Java) class I implemented is only "internally immutable" because it uses references to other mutable classes. In this case, the class under development appears from the external environment to have state. Do any of the benefits (see below) of immutable classes hold true even by only "internally immutable" classes? Is there an accepted term for the aforementioned "internal mutability"? Wikipedia's immutable object page uses the unsourced term "deep immutability" to describe an object whose references are also immutable. Is the distinction between mutability and side-effect-ness/state important? Josh Bloch lists the following benefits of immutable classes: are simple to construct, test, and use are automatically thread-safe and have no synchronization issues do not need a copy constructor do not need an implementation of clone allow hashCode to use lazy initialization, and to cache its return value do not need to be copied defensively when used as a field make good Map keys and Set elements (these objects must not change state while in the collection) have their class invariant established once upon construction, and it never needs to be checked again always have "failure atomicity" (a term used by Joshua Bloch) : if an immutable object throws an exception, it's never left in an undesirable or indeterminate state

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• Non-zero exit status for clean exit

  - by trinithis

  Is it acceptable to return a non-zero exit code if the program in question ran properly? For example, say I have a simple program that (only) does the following: Program takes N arguments. It returns an exit code of min(N, 255). Note that any N is valid for the program. A more realistic program might return different codes for successfully ran programs that signify different things. Should these programs instead write this information to a stream instead, such as to stdout?

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• Testing loses its effectiveness if all programmers don't use them

  - by Jeff O

  Let's assume you are convinced that the extra time spent unit testing has merit and improves production. Does that still hold up when everyone working on the same code doesn't use them? This question makes me wonder if fixing tests that everyone doesn't use is a waste of time. If you correct a test so the new code will pass, you're assuming the new code is correct. The person updating the test better have a firm understanding of the reasoning behind the code change and decide if the test or the new code needs to be fixed. This much inconsistency in a team when it comes to testing is probably an indication of other problems as well. There is a certain amount of risk involved that someone else on the team will alter code that is covered by testing. Is this the point where testing becomes counter-productive?

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• Is the 'C' in MVC really necessary?

  - by Anne Nonimus

  I understand the role of the model and view in the Model-View-Controller pattern, but I have a hard time understanding why a controller is necessary. Let's assume we're creating a chess program using an MVC approach; the game state should be the model, and the GUI should be the view. What exactly is the controller in this case? Is it just a separate class that has all the functions that will be called when you, say, click on a tile? Why not just perform all the logic on the model in the view itself?

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• Best practice settings Effect parameters in XNA

  - by hichaeretaqua

  I want to ask if there is a best practice settings effect parameters in XNA. Or in other words, what exactly happens when I call pass.Apply(). I can imagine multiple scenarios: Each time Apply() is called, all effect parameters are transferred to the GPU and therefor it has no real influence how often I set a parameter. Each time Apply() is called, only the parameters that got reset are transferred. So caching Set-operations that don't actually set a new value should be avoided. Each time Apply() is called, only the parameters that got changed are transferred. So caching Set-operations is useless. This whole questions is bootless because no one of the mentions ways has any noteworthy impact on game performance. So the final question: Is it useful to implement some caching of Set-operation like: private Matrix _world; public Matrix World { get{ return _world;} set { if(value == world)return; _effect.Parameters["xWorld"].SetValue(value); _world = value; } Thanking you in anticipation

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• AdventureWorks 2014 Sample Databases Are Now Available

  - by aspiringgeek

    Where in the World is AdventureWorks? Recently, SQL Community feedback from twitter prompted me to look in vain for SQL Server 2014 versions of the AdventureWorks sample databases we’ve all grown to know & love. I searched Codeplex, then used the bing & even the google in an effort to locate them, yet all I could find were samples on different sites highlighting specific technologies, an incomplete collection inconsistent with the experience we users had learned to expect.  I began pinging internally & learned that an update to AdventureWorks wasn’t even on the road map.  Fortunately, SQL Marketing manager Luis Daniel Soto Maldonado (t) lent a sympathetic ear & got the update ball rolling; his direct report Darmodi Komo recently announced the release of the shiny new sample databases for OLTP, DW, Tabular, and Multidimensional models to supplement the extant In-Memory OLTP sample DB.  What Success Looks Like In my correspondence with the team, here’s how I defined success: 1. Sample AdventureWorks DBs hosted on Codeplex showcasing SQL Server 2014’s latest-&-greatest features, including:  In-Memory OLTP (aka Hekaton) Clustered Columnstore Online Operations Resource Governor IO 2. Where it makes sense to do so, consolidate the DBs (e.g., showcasing Columnstore likely involves a separate DW DB) 3. Documentation to support experimenting with these features As Microsoft Senior SDE Bonnie Feinberg (b) stated, “I think it would be great to see an AdventureWorks for SQL 2014.  It would be super helpful for third-party book authors and trainers.  It also provides a common way to share examples in blog posts and forum discussions, for example.”  Exactly.  We’ve established a rich & robust tradition of sample databases on Codeplex.  This is what our community & our customers expect.  The prompt response achieves what we all aim to do, i.e., manifests the Service Design Engineering mantra of “delighting the customer”.  Kudos to Luis’s team in SQL Server Marketing & Kevin Liu’s team in SQL Server Engineering for doing so. Download AdventureWorks 2014 Download your copies of SQL Server 2014 AdventureWorks sample databases here.

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• Using IComparable<T> Interface

  - by Pawan_Mishra

  Level : Beginner to Intermediate C# language has constantly evolved over a constant period of time.Each new version introduced new features which changed the way we programmed and solved the problems. Whether it was introduction of generics in C# 2.0 , LINQ in C# 3.0 or concept of dynamic programming in C# 4.0 , each of them had or will have greater impact on our programming style.As a developer we don’t have much option but to evolve and redefine our self in this constantly changing environment...(read more)

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• The use of Test-Driven Development in Non-Greenfield Projects?

  - by JHarley1

  So here is a question for you, having read some great answers to questions such as "Test-Driven Development - Convince Me". So my question is: "Can Test-Driven Development be used effectively on non-Greenfield projects?" To specify: I would really like to know if people have had experience in using TDD in projects where there was already non-TDD elements present? And the problems that they then faced.

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• Why do programmers seem to be such bad spellers?

  - by Joel Etherton

  Programming languages are very precise tools based on explicit grammars. They're very picky, and when being used they require an exacting amount of detail. C#, for instance, is case sensitive so even getting the case of an argument wrong will cause an error. Questions asked all over the StackExchange are replete with misspellings, grammatical errors, and other problems that seem to indicate a lack of attention to detail when it comes to the language itself. Now, I understand there are a lot of programmers out there whose native language is not English, and I am not directing this question (rant one might say) at them. I'm referring to the individuals who are clearly from an English speaking background who refuse to pay attention to these simple details. I am not perfect by any means, but I try to use the language correctly so that my meaning will be understood correctly. I find programmers misspelling variable names, classes, and all manner of words in any kind of technical documentation they might write. I have had to withstand code where I am repeatedly referring to the subit[sic] button or HttpWebResponse reponse. The general complaint about bad spelling is one thing, and it will always be there. I accept that. But my question/comment is about the proclivity of bad spelling within the programming community. I would think that people who deal with such exacting tools to be more naturally predisposed towards proper spelling. Yet this doesn't seem to be the case.

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• How to avoid big and clumpsy UITableViewController on iOS?

  - by Johan Karlsson

  I have a problem when implementing the MVC-pattern on iOS. I have searched the Internet but seems not to find any nice solution to this problem. Many UITableViewController implementations seems to be rather big. Most example I have seen lets the UITableViewController implement UITableViewDelegate and UITableViewDataSource. These implementations are a big reason why UITableViewControlleris getting big. One solution would be to create separate classes that implements UITableViewDelegate and UITableViewDataSource. Of course these classes would have to have a reference to the UITableViewController. Are there any drawbacks using this solution? In general I think you should delegate the functionality to other "Helper" classes or similar, using the delegate pattern. Are there any well established ways of solving this problem? I do not want the model to contain to much functionality, nor the view. A believe that the logic should really be in the controller class, since this is one of the cornerstones of the MVC-pattern. But the big question is; How should you divide the controller of a MVC-implementation into smaller manageable pieces? (Applies to MVC in iOS in this case) There might be a general pattern for solving this, although I am specifically looking for a solution for iOS. Please give an example of a good pattern for solving this issue. Also an argument why this solution is awesome.

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• How to protect a peer-to-peer network from inappropriate content?

  - by Mike

  I’m developing a simple peer-to-peer app in .Net which should enable users to share specific content (text and picture files). As I've learned with my last question, inappropriate content can “relatively” easily be identified / controlled in a centralized environment. But what about a peer-to-peer network, what are the best methods to protect a decentralized system from unwanted (illegal) content? At the moment I only see the following two methods: A protocol (a set of rules) defines what kind of data (e.g. only .txt and jpg-files, not bigger than 20KB etc.) can be shared over the p2p-network and all clients (peers) must implement this protocol. If a peer doesn’t, it gets blocked by other peers. Pro: easy to implement. Con: It’s not possible to define the perfect protocol (I think eMail-Spam filters have the same problem) Some kind of rating/reputation system must be implemented (similar to stackoverflow), so “bad guys” and inappropriate content can be identified / blocked by other users. Pro: Would be very accurate. Con: Would be slow and in my view technically very hard to implement. Are there other/better solutions? Any answer or comment is highly appreciated.

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• Developing a feature which sole purpose to be taken out?

  - by adib

  What is the name of the pattern in which individual contributors (programmers/designers) developed an artifact for the sole purpose is to serve as a diversion so that management can remove that feature in the final product? This is a folklore I heard from an ex-colleague who used to work at a large game development company. At that company, it is well known that middle management is pressurized to "give inputs" and "make changes" to the product otherwise they risk being seen as not contributing to the project. This situation have delayed many projects because of these superfluous "management inputs". In one project at the above company, the artists and developers created a supernumerary animated character that appears in every cutscene and sticks out like a sore thumb. They designed it in such a way that it can be easily removed before the game is shipped (this was when games were still sold in physical media and not a downloadable product). Obviously the management then voted to remove the animation. On the positive side, management didn't introduced any unnecessary changes that would have delayed the project because they have shown that they provided constructive inputs to the product. This process pattern has a name among game programmers that work in corporates, but I forgot what was the actual name. I believe it's duck-something. Anybody can help pointing out the name and perhaps some rather credible reference to how the pattern develops?.

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• How do you think about an Application Generator? [closed]

  - by Mehdi Sheyda

  I'm designing an application-generating application. It is an application that takes the requirements of customer as inputs , analyzes the requirements, creates classes and produces program files in C#. I am at the beginning of this project and have a long way to go with this application. Do you have an experience with designing similar kinds of projects? What risks might I encounter with this project?

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• Is monkeypatching considered good programming practice?

  - by vartec

  I've been under impression, that monkeypatching is more in quick and dirty hack category, rather than standard, good programming practice. While I'd used from time to time to fix minor issues with 3rd party libs, I considered it temporary fix and I'd submit proper patch to the 3rd party project. However, I've seen this technique used as "the normal way" in mainstream projects, for example in Gevent's gevent.monkey module. Has monkeypatching became mainstream, normal, acceptable programming practice? See also: "Monkeypatching For Humans" by Jeff Atwood

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• Style bits vs. Separate bool's

  - by peterchen

  My main platform (WinAPI) still heavily uses bits for control styles etc. (example). When introducing custom controls, I'm permanently wondering whether to follow that style or rather use individual bool's. Let's pit them against each other: enum EMyCtrlStyles { mcsUseFileIcon = 1, mcsTruncateFileName = 2, mcsUseShellContextMenu = 4, }; void SetStyle(DWORD mcsStyle); void ModifyStyle(DWORD mcsRemove, DWORD mcsAdd); DWORD GetStyle() const; ... ctrl.SetStyle(mcsUseFileIcon | mcsUseShellContextMenu); vs. CMyCtrl & SetUseFileIcon(bool enable = true); bool GetUseFileIcon() const; CMyCtrl & SetTruncteFileName(bool enable = true); bool GetTruncteFileName() const; CMyCtrl & SetUseShellContextMenu(bool enable = true); bool GetUseShellContextMenu() const; ctrl.SetUseFileIcon().SetUseShellContextMenu(); As I see it, Pro Style Bits Consistent with platform less library code (without gaining complexity), less places to modify for adding a new style less caller code (without losing notable readability) easier to use in some scenarios (e.g. remembering / transferring settings) Binary API remains stable if new style bits are introduced Now, the first and the last are minor in most cases. Pro Individual booleans Intellisense and refactoring tools reduce the "less typing" effort Single Purpose Entities more literate code (as in "flows more like a sentence") No change of paradim for non-bool properties These sound more modern, but also "soft" advantages. I must admit the "platform consistency" is much more enticing than I could justify, the less code without losing much quality is a nice bonus. 1. What do you prefer? Subjectively, for writing the library, or for writing client code? 2. Any (semi-) objective statements, studies, etc.?

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• Am I missing a pattern?

  - by Ryan Pedersen

  I have a class that is a singleton and off of the singleton are properties that hold the instances of all the performance counters in my application. public interface IPerformanceCounters { IPerformanceCounter AccountServiceCallRate { get; } IPerformanceCounter AccountServiceCallDuration { get; } Above is an incomplete snippet of the interface for the class "PerformanceCounters" that is the singleton. I really don't like the plural part of the name and thought about changing it to "PerformanceCounterCollection" but stopped because it really isn't a collection. I also thought about "PerformanceCounterFactory" but it is really a factory either. After failing with these two names and a couple more that aren't worth mentioning I thought that I might be missing a pattern. Is there a name that make sense or a change that I could make towards a standardized pattern that would help me put some polish on this object and get rid of the plural name? I understand that I might be splitting hairs here but that is why I thought that the "Programmers" exchange was the place for this kind of thing. If it is not... I am sorry and I will not make that mistake again. Thanks!

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• Looking for some OO design advice

  - by Andrew Stephens

  I'm developing an app that will be used to open and close valves in an industrial environment, and was thinking of something simple like this:- public static void ValveController { public static void OpenValve(string valveName) { // Implementation to open the valve } public static void CloseValve(string valveName) { // Implementation to close the valve } } (The implementation would write a few bytes of data to the serial port to control the valve - an "address" derived from the valve name, and either a "1" or "0" to open or close the valve). Another dev asked whether we should instead create a separate class for each physical valve, of which there are dozens. I agree it would be nicer to write code like PlasmaValve.Open() rather than ValveController.OpenValve("plasma"), but is this overkill? Also, I was wondering how best to tackle the design with a couple of hypothetical future requirements in mind:- We are asked to support a new type of valve requiring different values to open and close it (not 0 and 1). We are asked to support a valve that can be set to any position from 0-100, rather than simply "open" or "closed". Normally I would use inheritance for this kind of thing, but I've recently started to get my head around "composition over inheritance" and wonder if there is a slicker solution to be had using composition?

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• How to write good code with new stuff?

  - by Reza M.

  I always try to write easily readable code that is well structured. I face a particular problem when I am messing around with something new. I keep changing the code, structure and so many other things. In the end, I look at the code and am annoyed at how complicated it became when I was trying to do something so simple. Once I've completed something, I refactor it heavily so that it's cleaner. This occurs after completion most of the time and it is annoying because the bigger the code the more annoying it is the rewrite it. I am curious to know how people deal with such agony, especially on big projects shared between many people ?

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• Builder Pattern: When to fail?

  - by skiwi

  When implementing the Builder Pattern, I often find myself confused with when to let building fail and I even manage to take different stands on the matter every few days. First some explanation: With failing early I mean that building an object should fail as soon as an invalid parameter is passed in. So inside the SomeObjectBuilder. With failing late I mean that building an object only can fail on the build() call that implicitely calls a constructor of the object to be built. Then some arguments: In favor of failing late: A builder class should be no more than a class that simply holds values. Moreover, it leads to less code duplication. In favor of failing early: A general approach in software programming is that you want to detect issues as early as possible and therefore the most logical place to check would be in the builder class' constructor, 'setters' and ultimately in the build method. What is the general concensus about this?

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• How to develop "Client script library" for ASP.net controls and how do these work?

  - by Niranjan Kala

  I have been working on .Net platform for 2 years and right now I am working on DevExpress controls for 6 months. All these control have client-side Events which are under some ClientScript nameSpace of particular control, Which specify ClientInstanceName, methods and properties accessible at client side. For example Button1 is ClientInstanceName and Button1.Text is a property, with methods like these: Button1.SetValue(); Button1.GetValue(); In ASP.Net Controls, buttons have the ClientClick event that fires before the Server Side Click event. I have inspected and goggled to extend client side functionality in asp.net controls. For example: create a ClientInstanceName property for controls or CheckedChanged event for CheckBox / RadioButton control. I have tried using these MSDN articles: Injecting Client-Side Script from an ASP.NET Server Control Working with Client-Side Script I got much information and ideas from these articles on how to implement/extend these. All are working in the client side. protected override void AddAttributesToRender(HtmlTextWriter writer) { base.AddAttributesToRender(writer); string script = @"return confirm(""%%POPUP_MESSAGE%%"");"; script = script.Replace("%%POPUP_MESSAGE%%", this.PopupMessage.Replace("\"", "\\\"")); writer.AddAttribute(HtmlTextWriterAttribute.Onclick, script); } Here It is just setting up attribute to the button. but all client side interaction no control from server. Here is that I want to know: How can I implement such functionality to create methods, properties etc. on client side. For example I am creating a PopControl as in the above code snippet same behavior as like Ajax ModalPopupExtender That have OK Button related properties. Ajax Controls can be directed to perform work from server side code e.g. Popup1.show(); How can I do this with such client enabled controls implemented controls as windows do? I am learning creation of Ajax Controls but I do not want to use ScriptManager or depend on another control. Just some extension to standard controls. I am expecting for ideas and implementation methods for such functionality.

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