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• asp.net Can I force every page to inherit from a base page? Also should some of this logic be in my master page?

  - by Bex

  Hi! I have a web app that has a base page. Each page needs to inherit from this base page as it contains properties they all need as well as dealing with the login rights. My base page has some properties, eg: IsRole1, IsRole2, currentUserID, Role1Allowed, Role2Allowed. On the init of each page I set the properties "Role1Allowed" and "Role2Allowed" Private Sub Page_Init(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Init Role1Allowed = True Role2Allowed= False End Sub The basepage then decides if the user needs redirecting. 'Sample code so not exactly what is going to be, bug gives the idea Protected Overridable Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) If Role1Allowed And Not Role1 Then 'Redirect somewhere End If End Sub The page then must override this pageload if they need anything else in it, but making sure they call the base pageload first. Protected Overrides Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load MyBase.Page_Load(sender, e) If Not IsPostBack Then BindGrid() End If End Sub The other properties (IsRole1, IsRole, currentUserID) are also accessible by the page so it can be decided if certain things need doing based on the user. (I hope this makes sense) Ok so I have 2 questions Should this functionality be in the base page or should it somehow be in the master, and if so how would I get access to all the properties if it was? As there are multiple people working on this project and creating pages some are forgetting to inherit from this basepage, or call the base pageload when overriding it. Is there any way to force them to do this? Thanks for any help. bex

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• Code excavations, wishful invocations, perimeters and domain specific unit test frameworks

  - by RoyOsherove

  One of the talks I did at QCON London was about a subject that I’ve come across fairly recently , when I was building SilverUnit – a “pure” unit test framework for silverlight objects that depend on the silverlight runtime to run. It is the concept of “cogs in the machine” – when your piece of code needs to run inside a host framework or runtime that you have little or no control over for testability related matters. Examples of such cogs and machines can be: your custom control running inside silverlight runtime in the browser your plug-in running inside an IDE your activity running inside a windows workflow your code running inside a java EE bean your code inheriting from a COM+ (enterprise services) component etc.. Not all of these are necessarily testability problems. The main testability problem usually comes when your code actually inherits form something inside the system. For example. one of the biggest problems with testing objects like silverlight controls is the way they depend on the silverlight runtime – they don’t implement some silverlight interface, they don’t just call external static methods against the framework runtime that surrounds them – they actually inherit parts of the framework: they all inherit (in this case) from the silverlight DependencyObject Wrapping it up? An inheritance dependency is uniquely challenging to bring under test, because “classic” methods such as wrapping the object under test with a framework wrapper will not work, and the only way to do manually is to create parallel testable objects that get delegated with all the possible actions from the dependencies.    In silverlight’s case, that would mean creating your own custom logic class that would be called directly from controls that inherit from silverlight, and would be tested independently of these controls. The pro side is that you get the benefit of understanding the “contract” and the “roles” your system plays against your logic, but unfortunately, more often than not, it can be very tedious to create, and may sometimes feel unnecessary or like code duplication. About perimeters A perimeter is that invisible line that your draw around your pieces of logic during a test, that separate the code under test from any dependencies that it uses. Most of the time, a test perimeter around an object will be the list of seams (dependencies that can be replaced such as interfaces, virtual methods etc.) that are actually replaced for that test or for all the tests. Role based perimeters In the case of creating a wrapper around an object – one really creates a “role based” perimeter around the logic that is being tested – that wrapper takes on roles that are required by the code under test, and also communicates with the host system to implement those roles and provide any inputs to the logic under test. in the image below – we have the code we want to test represented as a star. No perimeter is drawn yet (we haven’t wrapped it up in anything yet). in the image below is what happens when you wrap your logic with a role based wrapper – you get a role based perimeter anywhere your code interacts with the system: There’s another way to bring that code under test – using isolation frameworks like typemock, rhino mocks and MOQ (but if your code inherits from the system, Typemock might be the only way to isolate the code from the system interaction.   Ad-Hoc Isolation perimeters the image below shows what I call ad-hoc perimeter that might be vastly different between different tests: This perimeter’s surface is much smaller, because for that specific test, that is all the “change” that is required to the host system behavior.   The third way of isolating the code from the host system is the main “meat” of this post: Subterranean perimeters Subterranean perimeters are Deep rooted perimeters  - “always on” seams that that can lie very deep in the heart of the host system where they are fully invisible even to the test itself, not just to the code under test. Because they lie deep inside a system you can’t control, the only way I’ve found to control them is with runtime (not compile time) interception of method calls on the system. One way to get such abilities is by using Aspect oriented frameworks – for example, in SilverUnit, I’ve used the CThru AOP framework based on Typemock hooks and CLR profilers to intercept such system level method calls and effectively turn them into seams that lie deep down at the heart of the silverlight runtime. the image below depicts an example of what such a perimeter could look like: As you can see, the actual seams can be very far away form the actual code under test, and as you’ll discover, that’s actually a very good thing. Here is only a partial list of examples of such deep rooted seams : disabling the constructor of a base class five levels below the code under test (this.base.base.base.base) faking static methods of a type that’s being called several levels down the stack: method x() calls y() calls z() calls SomeType.StaticMethod()  Replacing an async mechanism with a synchronous one (replacing all timers with your own timer behavior that always Ticks immediately upon calls to “start()” on the same caller thread for example) Replacing event mechanisms with your own event mechanism (to allow “firing” system events) Changing the way the system saves information with your own saving behavior (in silverunit, I replaced all Dependency Property set and get with calls to an in memory value store instead of using the one built into silverlight which threw exceptions without a browser) several questions could jump in: How do you know what to fake? (how do you discover the perimeter?) How do you fake it? Wouldn’t this be problematic  - to fake something you don’t own? it might change in the future How do you discover the perimeter to fake? To discover a perimeter all you have to do is start with a wishful invocation. a wishful invocation is the act of trying to invoke a method (or even just create an instance ) of an object using “regular” test code. You invoke the thing that you’d like to do in a real unit test, to see what happens: Can I even create an instance of this object without getting an exception? Can I invoke this method on that instance without getting an exception? Can I verify that some call into the system happened? You make the invocation, get an exception (because there is a dependency) and look at the stack trace. choose a location in the stack trace and disable it. Then try the invocation again. if you don’t get an exception the perimeter is good for that invocation, so you can move to trying out other methods on that object. in a future post I will show the process using CThru, and how you end up with something close to a domain specific test framework after you’re done creating the perimeter you need.

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• Subterranean IL: Filter exception handlers

  - by Simon Cooper

  Filter handlers are the second type of exception handler that aren't accessible from C#. Unlike the other handler types, which have defined conditions for when the handlers execute, filter lets you use custom logic to determine whether the handler should be run. However, similar to a catch block, the filter block does not get run if control flow exits the block without throwing an exception. Introducing filter blocks An example of a filter block in IL is the following: .try { // try block } filter { // filter block endfilter }{ // filter handler } or, in v1 syntax, TryStart: // try block TryEnd: FilterStart: // filter block HandlerStart: // filter handler HandlerEnd: .try TryStart to TryEnd filter FilterStart handler HandlerStart to HandlerEnd In the v1 syntax there is no end label specified for the filter block. This is because the filter block must come immediately before the filter handler; the end of the filter block is the start of the filter handler. The filter block indicates to the CLR whether the filter handler should be executed using a boolean value on the stack when the endfilter instruction is run; true/non-zero if it is to be executed, false/zero if it isn't. At the start of the filter block, and the corresponding filter handler, a reference to the exception thrown is pushed onto the stack as a raw object (you have to manually cast to System.Exception). The allowed IL inside a filter block is tightly controlled; you aren't allowed branches outside the block, rethrow instructions, and other exception handling clauses. You can, however, use call and callvirt instructions to call other methods. Filter block logic To demonstrate filter block logic, in this example I'm filtering on whether there's a particular key in the Data dictionary of the thrown exception: .try { // try block } filter { // Filter starts with exception object on stack // C# code: ((Exception)e).Data.Contains("MyExceptionDataKey") // only execute handler if Contains returns true castclass [mscorlib]System.Exception callvirt instance class [mscorlib]System.Collections.IDictionary [mscorlib]System.Exception::get_Data() ldstr "MyExceptionDataKey" callvirt instance bool [mscorlib]System.Collections.IDictionary::Contains(object) endfilter }{ // filter handler // Also starts off with exception object on stack callvirt instance string [mscorlib]System.Object::ToString() call void [mscorlib]System.Console::WriteLine(string) } Conclusion Filter exception handlers are another exception handler type that isn't accessible from C#, however, just like fault handlers, the behaviour can be replicated using a normal catch block: try { // try block } catch (Exception e) { if (!FilterLogic(e)) throw; // handler logic } So, it's not that great a loss, but it's still annoying that this functionality isn't directly accessible. Well, every feature starts off with minus 100 points, so it's understandable why something like this didn't make it into the C# compiler ahead of a different feature.

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• What I like about WIF&rsquo;s Claims-based Authorization

  - by Your DisplayName here!

  In “traditional” .NET with its IPrincipal interface and IsInRole method, developers were encouraged to write code like this: public void AddCustomer(Customer customer) {     if (Thread.CurrentPrincipal.IsInRole("Sales"))     {         // add customer     } } In code reviews I’ve seen tons of code like this. What I don’t like about this is, that two concerns in your application get tightly coupled: business and security logic. But what happens when the security requirements change – and they will (e.g. members of the sales role and some other people from different roles need to create customers)? Well – since your security logic is sprinkled across your project you need to change the security checks in all relevant places (and make sure you don’t forget one) and you need to re-test, re-stage and re-deploy the complete app. This is clearly not what we want. WIF’s claims-based authorization encourages developers to separate business code and authorization policy evaluation. This is a good thing. So the same security check with WIF’s out-of-the box APIs would look like this: public void AddCustomer(Customer customer) {     try     {         ClaimsPrincipalPermission.CheckAccess("Customer", "Add");           // add customer     }     catch (SecurityException ex)     {         // access denied     } } You notice the fundamental difference? The security check only describes what the code is doing (represented by a resource/action pair) – and does not state who is allowed to invoke the code. As I mentioned earlier – the who is most probably changing over time – the what most probably not. The call to ClaimsPrincipalPermission hands off to another class called the ClaimsAuthorizationManager. This class handles the evaluation of your security policy and is ideally in a separate assembly to allow updating the security logic independently from the application logic (and vice versa). The claims authorization manager features a method called CheckAccess that retrieves three values (wrapped inside an AuthorizationContext instance) – action (“add”), resource (“customer”) and the principal (including its claims) in question. CheckAccess then evaluates those three values and returns true/false. I really like the separation of concerns part here. Unfortunately there is not much support from Microsoft beyond that point. And without further tooling and abstractions the CheckAccess method quickly becomes *very* complex. But still I think that is the way to go. In the next post I will tell you what I don’t like about it (and how to fix it).

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• Subterranean IL: Exception handler semantics

  - by Simon Cooper

  In my blog posts on fault and filter exception handlers, I said that the same behaviour could be replicated using normal catch blocks. Well, that isn't entirely true... Changing the handler semantics Consider the following: .try { .try { .try { newobj instance void [mscorlib]System.Exception::.ctor() // IL for: // e.Data.Add("DictKey", true) throw } fault { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } } filter { ldstr "2a: Filter logic" call void [mscorlib]System.Console::WriteLine(string) // IL for: // (bool)((Exception)e).Data["DictKey"] endfilter }{ ldstr "2b: Filter handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } } catch object { ldstr "3: Catch handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } Return: // rest of method If the filter handler is engaged (true is inserted into the exception dictionary) then the filter handler gets engaged, and the following gets printed to the console: 2a: Filter logic 1: Fault handler 2b: Filter handler and if the filter handler isn't engaged, then the following is printed: 2a:Filter logic 1: Fault handler 3: Catch handler Filter handler execution The filter handler is executed first. Hmm, ok. Well, what happens if we replaced the fault block with the C# equivalent (with the exception dictionary value set to false)? .try { // throw exception } catch object { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) rethrow } we get this: 1: Fault handler 2a: Filter logic 3: Catch handler The fault handler is executed first, instead of the filter block. Eh? This change in behaviour is due to the way the CLR searches for exception handlers. When an exception is thrown, the CLR stops execution of the thread, and searches up the stack for an exception handler that can handle the exception and stop it propagating further - catch or filter handlers. It checks the type clause of catch clauses, and executes the code in filter blocks to see if the filter can handle the exception. When the CLR finds a valid handler, it saves the handler's location, then goes back to where the exception was thrown and executes fault and finally blocks between there and the handler location, discarding stack frames in the process, until it reaches the handler. So? By replacing a fault with a catch, we have changed the semantics of when the filter code is executed; by using a rethrow instruction, we've split up the exception handler search into two - one search to find the first catch, then a second when the rethrow instruction is encountered. This is only really obvious when mixing C# exception handlers with fault or filter handlers, so this doesn't affect code written only in C#. However it could cause some subtle and hard-to-debug effects with object initialization and ordering when using and calling code written in a language that can compile fault and filter handlers.

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• SQL University: What and why of database refactoring

  - by Mladen Prajdic

  This is a post for a great idea called SQL University started by Jorge Segarra also famously known as SqlChicken on Twitter. It’s a collection of blog posts on different database related topics contributed by several smart people all over the world. So this week is mine and we’ll be talking about database testing and refactoring. In 3 posts we’ll cover: SQLU part 1 - What and why of database testing SQLU part 2 - What and why of database refactoring SQLU part 3 - Tools of the trade This is a second part of the series and in it we’ll take a look at what database refactoring is and why do it. Why refactor a database To know why refactor we first have to know what refactoring actually is. Code refactoring is a process where we change module internals in a way that does not change that module’s input/output behavior. For successful refactoring there is one crucial thing we absolutely must have: Tests. Automated unit tests are the only guarantee we have that we haven’t broken the input/output behavior before refactoring. If you haven’t go back ad read my post on the matter. Then start writing them. Next thing you need is a code module. Those are views, UDFs and stored procedures. By having direct table access we can kiss fast and sweet refactoring good bye. One more point to have a database abstraction layer. And no, ORM’s don’t fall into that category. But also know that refactoring is NOT adding new functionality to your code. Many have fallen into this trap. Don’t be one of them and resist the lure of the dark side. And it’s a strong lure. We developers in general love to add new stuff to our code, but hate fixing our own mistakes or changing existing code for no apparent reason. To be a good refactorer one needs discipline and focus. Now we know that refactoring is all about changing inner workings of existing code. This can be due to performance optimizations, changing internal code workflows or some other reason. This is a typical black box scenario to the outside world. If we upgrade the car engine it still has to drive on the road (preferably faster) and not fly (no matter how cool that would be). Also be aware that white box tests will break when we refactor. What to refactor in a database Refactoring databases doesn’t happen that often but when it does it can include a lot of stuff. Let us look at a few common cases. Adding or removing database schema objects Adding, removing or changing table columns in any way, adding constraints, keys, etc… All of these can be counted as internal changes not visible to the data consumer. But each of these carries a potential input/output behavior change. Dropping a column can result in views not working anymore or stored procedure logic crashing. Adding a unique constraint shows duplicated data that shouldn’t exist. Foreign keys break a truncate table command executed from an application that runs once a month. All these scenarios are very real and can happen. With the proper database abstraction layer fully covered with black box tests we can make sure something like that does not happen (hopefully at all). Changing physical structures Physical structures include heaps, indexes and partitions. We can pretty much add or remove those without changing the data returned by the database. But the performance can be affected. So here we use our performance tests. We do have them, right? Just by adding a single index we can achieve orders of magnitude performance improvement. Won’t that make users happy? But what if that index causes our write operations to crawl to a stop. again we have to test this. There are a lot of things to think about and have tests for. Without tests we can’t do successful refactoring! Fixing bad code We all have some bad code in our systems. We usually refer to that code as code smell as they violate good coding practices. Examples of such code smells are SQL injection, use of SELECT *, scalar UDFs or cursors, etc… Each of those is huge code smell and can result in major code changes. Take SELECT * from example. If we remove a column from a table the client using that SELECT * statement won’t have a clue about that until it runs. Then it will gracefully crash and burn. Not to mention the widely unknown SELECT * view refresh problem that Tomas LaRock (@SQLRockstar on Twitter) and Colin Stasiuk (@BenchmarkIT on Twitter) talk about in detail. Go read about it, it’s informative. Refactoring this includes replacing the * with column names and most likely change to application using the database. Breaking apart huge stored procedures Have you ever seen seen a stored procedure that was 2000 lines long? I have. It’s not pretty. It hurts the eyes and sucks the will to live the next 10 minutes. They are a maintenance nightmare and turn into things no one dares to touch. I’m willing to bet that 100% of time they don’t have a single test on them. Large stored procedures (and functions) are a clear sign that they contain business logic. General opinion on good database coding practices says that business logic has no business in the database. That’s the applications part. Refactoring such behemoths requires writing lots of edge case tests for the stored procedure input/output behavior and then start to refactor it. First we split the logic inside into smaller parts like new stored procedures and UDFs. Those then get called from the master stored procedure. Once we’ve successfully modularized the database code it’s best to transfer that logic into the applications consuming it. This only leaves the stored procedure with common data manipulation logic. Of course this isn’t always possible so having a plethora of performance and behavior unit tests is absolutely necessary to confirm we’ve actually improved the codebase in some way.   Refactoring is not a popular chore amongst developers or managers. The former don’t like fixing old code, the latter can’t see the financial benefit. Remember how we talked about being lousy at estimating future costs in the previous post? But there comes a time when it must be done. Hopefully I’ve given you some ideas how to get started. In the last post of the series we’ll take a look at the tools to use and an example of testing and refactoring.

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• The worst anti-patterns you have came across.

  - by ?????????

  What are the worst anti-patterns you have came across in your career as a programmer? I'm mostly involved in java, although it is probably language-independent. I think the worst of it is what I call the main anti-pattern. It means program consisting of single, extremely big class (sometimes accompanied with a pair of little classes) which contains all logic. Typically with a big loop in which all business logic is contained, sometimes having tens of thousands of lines of code.

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• links for 2010-12-22

  - by Bob Rhubart

  @hajonormann: BPM: Top Seven Architectural Topics in 2010 Oracle ACE Director Hajo Normann offers details on how to design a BPM/SOA solution including: modeling human interaction, improving BPM models, orchestrating composed services, central task management, new approaches for business-IT alignment, solutions for non-deterministic processes, and choreography. (tags: oracle otn soasymposium infoq soa bpm) InfoQ: Simplicity, The Way of the Unusual Architect Dan North talks about the tendency developers-becoming-architects have to create bigger and more complex systems. Without trying to be simplistic, North argues for simplicity, offering strategies to extract the simple essence from complex situations. (tags: ping.fm) Fun with Sun Ray, 3D, Oracle VM x86 and SRIOV (Wim Coekaerts Blog) "One of the things I like about my job is that I get to play around with stuff and make use of the technologies we work on in my teams. Sort of my own little playground." - Wim Coekaerts (tags: oracle otn virtualization oraclevm) Oracle VM VirtualBox 4.0.0 Released! (Oracle's Virtualization Blog) And you were worried about what to get that special someone for Christmas... (tags: oracle otn virtualization virtualbox) Virtual Developer Day: Oracle WebLogic Server & Java EE (#OTNVDD) (Oracle Technology Network Blog (aka TechBlog)) "Virtual Developer Day is back with a vengeance! On Feb. 1, login to learn how Oracle WebLogic Server enables a whole new level of productivity for enterprise developers." Registration is open. (tags: oracle otn events webinar java) New Coherence 3.6 Oracle University Course (Cristóbal Soto's Blog) Cristóbal Soto shares information on the "Oracle Coherence 3.6: Share and Manage Data in Clusters" course now available through Oracle University. (tags: oracle otn grid coherence) The Aquarium: Oracle WebLogic Server & Java EE developer day "Oracle WebLogic is well on its way to contribute to the general Java EE 6 momentum and the OTN Blog has just announced a Virtual Developer Day for Oracle WebLogic." (tags: oracle otn weblogic java) Enterprise 2.0 Use Cases for Semantic Web (Reiser 2.0) "How can an enterprise improve the efficiency and effectiveness of their Knowledge and Community model leveraging semantic technologies and social networking dynamics?" - Peter Reiser (tags: oracle otn enterprise2.0 semanticweb) John Gøtze: European Interoperability Framework 2.0 "This week, the European Commission announced an updated interoperability policy in the EU. The Commission has committed itself to adopt a Communication that introduces the European Interoperability Strategy (EIS) and an update to the European Interoperability Framework (EIF)..." - John Gøtze (tags: entarch Interoperability) Andy Mulholland: Maybe Web 3.0 is quite understandable – and a natural result "The idea of Web 1.0 = content, Web 2.0 = people and Web 3.0 = services has a nice symmetrical feel to it, in fact it feels basically right as such a definition would include the two other major definitions as well. So if we put these things all together what picture do we see?" - Andy Mulholland (tags: web2.0 web3.0) Ken Downs: A Working Definition of Business Logic, with Implications for CRUD Code "The Wikipedia entry on 'Business Logic' has a wonderfully honest opening sentence stating that 'Business logic, or domain logic, is a non-technical term...'"  (tags: businesslogic crud)

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• What is a good design model for my new class?

  - by user66662

  I am a beginning programmer who, after trying to manage over 2000 lines of procedural php code, now has discovered the value of OOP. I have read a few books to get me up to speed on the beginning theory, but would like some advice on practical application. So,for example, let's say there are two types of content objects - an ad and a calendar event. what my application does is scan different websites (a predefined list), and, when it finds an ad or an event, it extracts the data and saves it to a database. All of my objects will share a $title and $description. However, the Ad object will have a $price and the Event object will have $startDate. Should I have two separate classes, one for each object? Should I have a 'superclass' with the $title and $description with two other Ad and Event classes with their own properties? The latter is at least the direction I am on now. My second question about this design is how to handle the logic that extracts the data for $title, $description, $price, and $date. For each website in my predefined list, there is a specific regex that returns the desired value for each property. Currently, I have an extremely large switch statement in my constructor which determines what website I am own, sets the regex variables accordingly, and continues on. Not only that, but now I have to repeat the logic to determine what site I am on in the constructor of each class. This doesn't feel right. Should I create another class Algorithms and store the logic there for each site? Should the functions of to handle that logic be in this class? or specific to the classes whos properties they set? I want to take into account in my design two things: 1) I will add different content objects in the future that share $title and $description, but will have their own properties, so, I want to be able to easily grow these as needed. 2) I will add more websites constantly (each with their own algorithms for data extraction) so I would like to plan efficienty managing and working with these now. I thought about extending the Ad or Event class with 'websiteX' class and store its functions there. But, this didn't feel right either as now I have to manage 100s of little website specific class files. Note, I didn't know if this was the correct site or stackoverflow was the better choice. If so, let me know and I'll post there.

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• Download LINQExtender

  - by Editor

  LinqExtender is a toolkit for creating custom LINQ providers without knowing anything of how expression is parsed or processed and focusing on only the business logic. You just need to extend its query class , declare the query object and override some methods to put your logic and its done. Getting Started You can [...]

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• Should Item Grouping/Filter be in the ViewModel or View layer?

  - by ronag

  I'm in a situation where I have a list of items that need to be displayed depending on their properties. What I'm unsure of is where is the best place to put the filtering/grouping logic of the viewmodel state? Currently I have it in my view using converters, but I'm unsure whether I should have the logic in the viewmodel? e.g. ViewModel Layer: class ItemViewModel { DateTime LastAccessed { get; set; } bool IsActive { get; set; } } class ContainerViewModel { ObservableCollection<Item> Items {get; set;} } View Layer: <TextView Text="Active Items"/> <List ItemsSource={Binding Items, Converter=GroupActiveItemsByDay}/> <TextView Text="Active Items"/> <List ItemsSource={Binding Items, Converter=GroupInActiveItemsByDay}/> or should I build it like this? ViewModel Layer: class ContainerViewModel { ObservableCollection<IGrouping<string, Item>> ActiveItemsByGroup {get; set;} ObservableCollection<IGrouping<string, Item>> InActiveItemsByGroup {get; set;} } View Layer: <TextView Text="Active Items"/> <List ItemsSource={Binding ActiveItemsGroupByDate }/> <TextView Text="Active Items"/> <List ItemsSource={Binding InActiveItemsGroupByDate }/> Or maybe something in between? ViewModel Layer: class ContainerViewModel { ObservableCollection<IGrouping<string, Item>> ActiveItems {get; set;} ObservableCollection<IGrouping<string, Item>> InActiveItems {get; set;} } View Layer: <TextView Text="Active Items"/> <List ItemsSource={Binding ActiveItems, Converter=GroupByDate }/> <TextView Text="Active Items"/> <List ItemsSource={Binding InActiveItems, Converter=GroupByDate }/> I guess my question is what is good practice in terms as to what logic to put into the ViewModel and what logic to put into the Binding in the View, as they seem to overlap a bit?

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• Specification

  Generally saying Specification is a predicate that determines if an object does or does not satisfy some criteria. By using Specifications you could easily recombine business logic together using boolean logic.Have you ever thought that bool TryParse(string s, out int result) is pattern?

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• How to diagnose and solve an erratic "HDCP Support Required"?

  - by Jom Orgstrom

  I am playing a digital tv broadcast on Windows Media Center for Windows 7. I built this system so it works with HDCP, and in fact I have been able to watch tv and bluray before with this same computer. However, I suddenly started getting an "HDCP Support Required" error from WMC. The entire message is as follows: HDCP Support Required High-bandwidth Digital Content Protection (HDCP) may not be supported by the current video card. Use an HDCP-compliant display, video card, and video driver. Or, connect using an analog connection such as component or VGA. Relevant specs are: CPU: Ivy Bridge Core i7-3770 Motherboard: Asus P8H77-I Memory: 16GB DDR3-1600 Graphics: Radeon HD 7850 (Driver by AMD, version 8.982.0.0 built on 2012/07/27) Display: Acer P243w connected by HDMI Sound: Roland Quad-Capture (It complains even when I use the bundled VIA HD Audio) TV Tuner: I-O Data GV-MC7/HZ3 OS: Windows 7 Professional SP1, Windows Update enabled. All patched and up to date. As you can see, there is nothing weird or old about my setup. I am also not doing anything strange, not doing any overclocking, weird system changes and so on. One thing that does happen from time to time, is that the display goes black for a few seconds (sometimes when watching media contents, sometimes when just using photoshop or Visual Studio). This happened with my previous setup as well, so I'd be inclined to think it is a display or cable issue (apart from the BD drive, these are the only things I kept from my previous setup to this one). But being a digital transfer, as far as I know, these things either work or not. Never erratically or with decreased quality. The thing is that sometimes I can watch the TV, sometimes not. This happens with recorded programs as well, so it's not a per-program thing. Sometimes rebooting helps, sometimes it doesn't. Sometimes unplugging and plugging back the HDMI connector helps, sometimes it doesn't. Sometimes doing so doesn't even turn the screen back on, so I have to reboot. Unfortunately, WMC's error message is quite unhelpful. I'd like to know exactly where the problem is, so I can solve it. I don't want to buy a brand new display just to then find out it was a registry setting that was misconfigured. I've tried looking at the system event viewer, but these errors don't show up at all in there. Other people who have this problem seem to have a setup that is not HDCP compliant, so I turn to you guys here. Anybody knows how to diagnose this problem? Edit: So I got the Cyberlink Blu-ray disc advisor. I ran it and told me everything was okay, except for the Video Connection Type, which showed as "Digital (without HDCP)". I then proceeded to unplug the power cable from the monitor, plugged it in again, ran the tool again, and now it's "Digital (with HDCP)". Needless to say, I can watch my TV and recorded programs on WMP again. I'm guessing that at some point, something may be slightly wrong with the HDCP setup, and Windows decides to reset the entire content protection path (which leads to the screen blanking out). Usually the reset succeeds, but sometimes it doesn't, so Windows defaults to turning HDCP off. There's no way to turn it back on, except by doing a hard reset of the display. I really want to know what the exact error was, so I can fix it. Is it the cable? is it the display? is it the video card? the driver? Also, is there any other way to try and turn HDCP on again without having to hard reset the display? Oh, questions, questions...

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• Session Report: What’s New in JSF: A Complete Tour of JSF 2.2

  - by Janice J. Heiss

  On Wednesday, Ed Burns, Consulting Staff Member at Oracle, presented a session, CON3870 -- “What’s New in JSF: A Complete Tour of JSF 2.2,” in which he provided an update on recent developments in JavaServer Faces 2.2. He began by emphasizing that, “JavaServer Faces 2.2 continues the evolution of the Java EE standard user interface technology. Like previous releases, this iteration is very community-driven and transparent.” He pointed out that since JSF was introduced at the 2001 JavaOne Keynote, it has had a long and successful run and has found a home in applications where the UI logic resides entirely on the server where the model and UI logic is. In such cases, the browser performs fairly simple functions. However, developers can take advantage of the power of browsers, something that Project Avatar is focused on by letting developers author their applications so the UI logic is running on the client and communicating to the back end via RESTful web services. “Most importantly,” remarked Burns, “JSF 2.2 offers a really good migration path because even in the scope of one application you could have an app written with JSF that has its UI logic on the server and, on a gradual basis, you could migrate parts of the app over to use client-side technologies. This can be done at any level of granularity – per page or per collection of pages. It all depends on what you want to do.” His presentation, which focused on the basic new features of JSF 2.2, began by restating the scope of JSF and encouraged attendees to check out Roger Kitain’s session: CON5133 “Techniques for Responsive Real-Time Web UIs.” Burns explained that JSF has endured because, “We still need web apps that are maintainable, localizable, quick to build, accessible, secure, look great and are fun to use.” It is used on every continent – the curious can go here to check out where its unofficial usage is tracked. He emphasized the significance of the UI logic being substantially on the server. This: Separates Component Semantics from Rendering, Allows components to “own” their little patch of the UI -- encode/decode, And offers a well-defined lifecycle: Inversion of Control. Burns reminded attendees that JSR-344, the spec for JSF 2.2, is now on Java Community Process 2.8, a revised version of the JCP that allows for more openness and transparency. He then offered some tools for community access to JSF 2.2:    * Public java.net projects spec http://jsf-spec.java.net/ impl http://jsf.java.net/ Open Source: GPL+Classpath Exception    * Mailing Lists [email protected]                                Public readable archive, JSPA signed member read/write [email protected]                                     Public readable archive, any java.net member read/write                         All mail sent to jsr344-experts is sent to users. * Issue Tracker spec http://jsf-spec.java.net/issues/ impl http://jsf.java.net/issues/ JSF 2.2, which is JSR 344, has a Public Review Draft planned by December 2012 with no need for a Renewal Ballot. The Early Draft Review of JSR 344 was published on December 8, 2011. Interested developers are encouraged to offer their input. Six Big Ticket Features of JSF 2.2 Burns summarized the six big ticket features of JSF 2.2:* HTML5 Friendly Markup Support Pass through attributes and elements * Faces Flows* Cross Site Request Forgery Protection* Loading Facelets via ResourceHandler* File Upload Component* Multi-Templating He explained that he called it “HTML 5 friendly” because there is really nothing HTML 5 specific about it -- it could be 4. But it enables developers to use new elements that are present in HTML5 without having a JSF component library that is written to take advantage of those specifically. It gives the page author the ability to use plain HTML5 to write their page, but to still take advantage of the server-side available in JSF. He presented a demo showing JSF 2.2’s ability to leverage the expressiveness of HTML5. Burns then explained the significance of face flows, which offer function points and quantify how much work has taken place, something of great value to JSF users. He went on to talk about JSF 2.2.’s cross-site request forgery protection (CSRF) and offered details about how it protects applications against attack. Then he talked about JSF 2.2’s File Upload Component and explained that the final specification will have Ajax and non-Ajax support. The current milestone has non-Ajax support implemented. He then went on to explain its capacity to add facelets through ResourceHandler. Previously, JSF 2.0 added Facelets and ResourceHandler as disparate units; now in JSF 2.2 the two concepts are unified. Finally, he explained the concept of multi-templating in JSF 2.2 and went on to discuss more medium-level features of the release. For an easy, low maintenance way of staying in touch with JSF developments go to JSF’s Twitter page where every month or so, important updates are offered.

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• Access Services in SharePoint Server 2010

  - by Wayne

  Another SharePoint Server 2010 feature which cannot go unnoticed is the Access Services. Access Services is a service in SharePoint Server 2010 that allows administrators to view, edit, and configure a Microsoft access application within a Web Browser. Access Services settings support backup and recovery, regardless of whether there is a UI setting in Central Administration. However, backup and recovery only apply to service-level and administrative-level settings; end-user content from the Access application is not backed up as part of this process. Access Services has Windows PowerShell functionality that can be used to provide the service that uses settings from a previous backup; configure and manage macro and query setting; manage and configure session management; and configure all the global settings of the service. Key Benefits of SharePoint Server Access Services Easier Access to right tools: The enhanced, customizable Ribbon in Access 2010 makes it easy to uncover more commands so you can focus on the end product. The new Microsoft Office BackstageTM view is yet another feature that can help you easily analyze and document your database, share, publish, and customize your Access 2010 experience, all from one convenient location. Helps build database effortlessly and quickly: Out-of-the box templates and reusable components make Access Services the fastest, simplest database solution available. It helps find new pre-built templates which you can start using without customization or select templates created by your peers in the Access online community and customize them to meet your needs. It builds your databases with new modular components. New Application Parts enable you to add a set of common Access components, such as a table and form for task management, to your database in a few simple clicks. Database navigation is now simplified. It creates Navigation Forms and makes your frequently used forms and reports more accessible without writing any code or logic. Create Impactful forms and reports: Whether it's an inventory of your assets or customer sales database, Access 2010 brings the innovative tools you'd expect from Microsoft Office. Access Services easily spot trends and add emphasis to your data. It quickly create coordinating database forms and reports and bring the Web into your database. Obtain a centralized landing pad for your data: Access 2010 offers easy ways to bring your data together and help increase work quality. New technologies help break down barriers so you can share and work together on your databases, making you or your team more efficient and productive. Add automation and complex expressions: If you need a more robust database design, such as preventing record deletion if a specific condition is met or if you need to create calculations to forecast your budget, Access 2010 empowers you to be your own developer. The enhanced Expression Builder greatly simplifies your expression building experience with IntelliSense®. With the revamped Macro Designer, it's now even easier for you to add basic logic to your database. New Data Macros allow you to attach logic to your data, centralizing the logic on the table, not the objects that update your data. Key features of Access Services 2010 - Access database content through a Web browser: Newly added Access Services on Microsoft SharePoint Server 2010 enables you to make your databases available on the Web with new Web databases. Users without an Access client can open Web forms and reports via a browser and changes are automatically synchronized. - Simplify how you access the features you need: The Ribbon, improved in Access 2010, helps you access commands even more quickly by enabling you to customize or create your own tabs. The new Microsoft Office Backstage view replaces the traditional File menu to provide one central, organized location for all of your document management tasks. - Codeless navigation: Use professional looking web-like navigation forms to make frequently used forms and reports more accessible without writing any code or logic. - Easily reuse Access items in other databases: Use Application Parts to add pre-built Access components for common tasks to your database in a few simple clicks. You can also package common database components, such as data entry forms and reports for task management, and reuse them across your organization or other databases. - Simplified formatting: By using Office themes you can create coordinating professional forms and reports across your database. Simply select a familiar and great looking Office theme, or design your own, and apply it to your database. Newly created Access objects will automatically match your chosen theme.

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• ADF Business Components

  - by Arda Eralp

  ADF Business Components and JDeveloper simplify the development, delivery, and customization of business applications for the Java EE platform. With ADF Business Components, developers aren't required to write the application infrastructure code required by the typical Java EE application to: Connect to the database Retrieve data Lock database records Manage transactions   ADF Business Components addresses these tasks through its library of reusable software components and through the supporting design time facilities in JDeveloper. Most importantly, developers save time using ADF Business Components since the JDeveloper design time makes typical development tasks entirely declarative. In particular, JDeveloper supports declarative development with ADF Business Components to: Author and test business logic in components which automatically integrate with databases Reuse business logic through multiple SQL-based views of data, supporting different application tasks Access and update the views from browser, desktop, mobile, and web service clients Customize application functionality in layers without requiring modification of the delivered application The goal of ADF Business Components is to make the business services developer more productive.   ADF Business Components provides a foundation of Java classes that allow your business-tier application components to leverage the functionality provided in the following areas: Simplifying Data Access Design a data model for client displays, including only necessary data Include master-detail hierarchies of any complexity as part of the data model Implement end-user Query-by-Example data filtering without code Automatically coordinate data model changes with business services layer Automatically validate and save any changes to the database   Enforcing Business Domain Validation and Business Logic Declaratively enforce required fields, primary key uniqueness, data precision-scale, and foreign key references Easily capture and enforce both simple and complex business rules, programmatically or declaratively, with multilevel validation support Navigate relationships between business domain objects and enforce constraints related to compound components   Supporting Sophisticated UIs with Multipage Units of Work Automatically reflect changes made by business service application logic in the user interface Retrieve reference information from related tables, and automatically maintain the information when the user changes foreign-key values Simplify multistep web-based business transactions with automatic web-tier state management Handle images, video, sound, and documents without having to use code Synchronize pending data changes across multiple views of data Consistently apply prompts, tooltips, format masks, and error messages in any application Define custom metadata for any business components to support metadata-driven user interface or application functionality Add dynamic attributes at runtime to simplify per-row state management   Implementing High-Performance Service-Oriented Architecture Support highly functional web service interfaces for business integration without writing code Enforce best-practice interface-based programming style Simplify application security with automatic JAAS integration and audit maintenance "Write once, run anywhere": use the same business service as plain Java class, EJB session bean, or web service   Streamlining Application Customization Extend component functionality after delivery without modifying source code Globally substitute delivered components with extended ones without modifying the application   ADF Business Components implements the business service through the following set of cooperating components: Entity object An entity object represents a row in a database table and simplifies modifying its data by handling all data manipulation language (DML) operations for you. These are basically your 1 to 1 representation of a database table. Each table in the database will have 1 and only 1 EO. The EO contains the mapping between columns and attributes. EO's also contain the business logic and validation. These are you core data services. They are responsible for updating, inserting and deleting records. The Attributes tab displays the actual mapping between attributes and columns, the mapping has following fields: Name : contains the name of the attribute we expose in our data model. Type : defines the data type of the attribute in our application. Column : specifies the column to which we want to map the attribute with Column Type : contains the type of the column in the database   View object A view object represents a SQL query. You use the full power of the familiar SQL language to join, filter, sort, and aggregate data into exactly the shape required by the end-user task. The attributes in the View Objects are actually coming from the Entity Object. In the end the VO will generate a query but you basically build a VO by selecting which EO need to participate in the VO and which attributes of those EO you want to use. That's why you have the Entity Usage column so you can see the relation between VO and EO. In the query tab you can clearly see the query that will be generated for the VO. At this stage we don't need it and just use it for information purpose. In later stages we might use it. Application module An application module is the controller of your data layer. It is responsible for keeping hold of the transaction. It exposes the data model to the view layer. You expose the VO's through the Application Module. This is the abstraction of your data layer which you want to show to the outside word.It defines an updatable data model and top-level procedures and functions (called service methods) related to a logical unit of work related to an end-user task. While the base components handle all the common cases through built-in behavior, customization is always possible and the default behavior provided by the base components can be easily overridden or augmented. When you create EO's, a foreign key will be translated into an association in our model. It defines the type of relation and who is the master and child as well as how the visibility of the association looks like. A similar concept exists to identify relations between view objects. These are called view links. These are almost identical as association except that a view link is based upon attributes defined in the view object. It can also be based upon an association. Here's a short summary: Entity Objects: representations of tables Association: Relations between EO's. Representations of foreign keys View Objects: Logical model View Links: Relationships between view objects Application Model: interface to your application  

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• speakers dont work in macbook pro

  - by Ali_IT

  I have a macbook pro but my Built-in stereo speakers don't work and it comes a red light from Headphone out/optical digital audio out port. my Built-in stereo speakers aren't dead because at first that OS runs it comes a sound from them but as soon as the macbook pro is ready when i play music they don't work and In the SOUND in system preferences the name of device for sound output is Digital Out. Is the problem from hardware or software. Is there any solution?

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• Software for "OCR"'ing exact pixels from a photo of a videogame/pixel-art?

  - by Grumbel

  I am searching for software that can reconstruct the exact pixels from a photo of an old videogame or a piece pixel-art. The goal would be the re-digitalization of digital images that only survived in an analog copy, say images of Mario Paint that where captured on a VHS tape or old digital art that only survived as a printout. Does such software exist?

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• Task-dedicated computers for the household?

  - by Matias Nino

  This question is to generate ideas for task-dedicated computers in a household. Here's mine: Personal Desktop - Gaming, working, office productivity, entertainment, CD/DVD burning General Server - backups, application hosting, mail server, file server, VM server, torrent seeding Personal Laptop - software development, mobile computing Media Center PC - Digital media playback, media file server, Gaming Photo PC - Digital photo management/archival. Nightstand Netbook - Bedtime surfing/reading Spare Laptop - general household use

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• How can Rackspace beat DigitalOcean's Pricepoint? [on hold]

  - by Matt Jensen

  I have recently discovered Digital Ocean and I have found it to be a relatively nice experience for small staging servers, and the thought occurred to me, why am I paying $267~ for a server on Rackspace (40GB RAM, 160 GB Drive, 2 vCPUs, 400 Mb/s) when Digital Ocean offers a server for $40 (40 GB RAM, 60GB Drive [storage is not a concern of mine], 2 vCPUs, ?Mb/s)? Does Rackspace offer some kind of obvious advantages in Transfer speed/bandwidth? My applications are small startups that for the immediate future will only have about 200-300 concurrent users at once.

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• Strange monitor issue - screen goes black after a few seconds

  - by Scott Szretter

  My LCD monitor display is going black (turning off). It's a Samsung SYncMaster 2233 widescreen. I am trying to figure out if there is anything I can do about it, or if the monitor is junk. I have tried multiple computers, all have the same issue. I have tried a different vga cable, same issue. Power and video cables are tight / double checked. When I power on the monitor, the blue light turns on at the bottom. Then a second or two later the video comes up as expected and it looks fine. However, about 2-3 seconds after that, the screen goes black. The blue light is still on and solid at the bottom (blue light normally flashes when the monitor is sleeping). If I power cycle the monitor, same thing happens. With no computer connected or when I unplug the vga cable, I see the searching for signal message "digital", then the screen goes black. However it usually shows "digital" then "analog" after that and switches between the two a few times. The buttons on the side do not do anything, although they may be, I just can not see if they are or not. I can usually get the "digital" message by pressing the buttons on the side, but then it quickly goes black again. What is really strange is sometimes I can get it to work fine. I am not sure what the difference is. Last week I connected it up and it worked fine and it stayed fine for at least a week! I did not turn it off or anything, I just let the OS put the display to sleep. Then this week one morning I started having the screen going black issue again. Seems like something is either loose inside or beginning to fail. Do you think there is any hope for it? update: pushing the input select button causes the "digital" and "analog" messages to flash on the screen, but only for a few seconds then it goes black. When it was working properly, those messages would flash back and fourth for probably 10-20 seconds then a message would show saying check input signal, but now just a black screen.

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• Can not get sound over hdmi in kubuntu 9.10

  - by user32509

  I have used a hdmi cable to connect my lcd (which is connected with my speakers) with my nvida 275 gtx grafic card. I can not get the sound output to work. The hardware itself is working probably - I tested it under windows. Currently I am running Kubuntu 9.10 64 with Nvidia 190.53. The sound output worked fine before I installed the hdmi connection. (German output - i can change it, if you tell me how :)) aplay -l **** Liste von PLAYBACK Geräten **** Karte 0: Intel [HDA Intel], Gerät 0: ALC889A Analog [ALC889A Analog] Untergeordnete Geräte: 1/1 Untergeordnetes Gerät '0: subdevice #0 Karte 0: Intel [HDA Intel], Gerät 1: ALC889A Digital [ALC889A Digital] Untergeordnete Geräte: 1/1 Untergeordnetes Gerät '0: subdevice #0 aplay -L front:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog Front speakers surround40:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog 4.0 Surround output to Front and Rear speakers surround41:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog 4.1 Surround output to Front, Rear and Subwoofer speakers surround50:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog 5.0 Surround output to Front, Center and Rear speakers surround51:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog 5.1 Surround output to Front, Center, Rear and Subwoofer speakers surround71:CARD=Intel,DEV=0 HDA Intel, ALC889A Analog 7.1 Surround output to Front, Center, Side, Rear and Woofer speakers iec958:CARD=Intel,DEV=0 HDA Intel, ALC889A Digital IEC958 (S/PDIF) Digital Audio Output null Discard all samples (playback) or generate zero samples (capture) pulse Playback/recording through the PulseAudio sound server And i disabled mute in kmix an all channels :) Edit: lspci -v ... 00:1b.0 Audio device: Intel Corporation 82801I (ICH9 Family) HD Audio Controller (rev 02) Subsystem: Giga-byte Technology Device a022 Flags: bus master, fast devsel, latency 0, IRQ 22 Memory at ea400000 (64-bit, non-prefetchable) [size=16K] Capabilities: [50] Power Management version 2 Capabilities: [60] Message Signalled Interrupts: Mask- 64bit+ Queue=0/0 Enable- Capabilities: [70] Express Root Complex Integrated Endpoint, MSI 00 Capabilities: [100] Virtual Channel <?> Capabilities: [130] Root Complex Link <?> Kernel driver in use: HDA Intel Kernel modules: snd-hda-intel ... cat /proc/asound/version Advanced Linux Sound Architecture Driver Version 1.0.20. lsmod | grep snd_hda_intel snd_hda_intel 31880 2 snd_hda_codec 87584 2 snd_hda_codec_realtek,snd_hda_intel snd_pcm 93160 3 snd_hda_intel,snd_hda_codec,snd_pcm_oss snd 77096 16 snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_seq_oss,snd_rawmidi,snd_seq,snd_timer,snd_seq_device snd_page_alloc 10928 2 snd_hda_intel,snd_pcm I think I am missing the something-hdmi module? Is there such a thing?

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• XML Signature in a Web application

  - by OpenDevSoft

  Hi, We are developing an e-Banking web application for a small bank (up to 20000 clients/users). We have to implement digital signatures with X509 certificates (issued by CA on USB tokens) for signing payment information. We tried using CAPICOM but it seems that it is not working well with Windows Vista (have not tried it with Win 7). The other problem is that core banking system can process only Xml digital signatures, so we have to sign XML documents (not just a bulk-formatted text data like with CAPICOM and Win32 Crypto API). So my questions here are: Does anyone of you have similar problem and how did they solved it? Is there a plug-in, library, component or external tool (for Internet Explorer and/or Fire Fox) that supports XML Digital Signatures in a web application? Can you please recommend some of these products and write something about your experience with them? Thank you very much.

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• Problem in VS2010 IDE in analog monitor in a dual-monitor setup

  - by Samik R.

  I am using VS2010 Premium with a dual-window setup. One of the monitors is on a digital (DVI) cable and other one is on an analog (VGA) cable. I have noticed that when I put VS2010 in the analog monitor, there are garbled texts and refresh problems while coding and/or scrolling. This does not seem to be the case when I put VS2010 in the digital monitor. Note that, I am not expanding VS IDE to use 2 screens, just making it 1 full screen, either analog or digital. Has anyone else experienced this problem? I also work with VS2008 and have not seen this problem in either screen. VS IDE has started using WPF from the 2010 release, not sure if this has something to do with it.

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• How to generalize a method call in Java (to avoid code duplication)

  - by dln385

  I have a process that needs to call a method and return its value. However, there are several different methods that this process may need to call, depending on the situation. If I could pass the method and its arguments to the process (like in Python), then this would be no problem. However, I don't know of any way to do this in Java. Here's a concrete example. (This example uses Apache ZooKeeper, but you don't need to know anything about ZooKeeper to understand the example.) The ZooKeeper object has several methods that will fail if the network goes down. In this case, I always want to retry the method. To make this easy, I made a "BetterZooKeeper" class that inherits the ZooKeeper class, and all of its methods automatically retry on failure. This is what the code looked like: public class BetterZooKeeper extends ZooKeeper { private void waitForReconnect() { // logic } @Override public Stat exists(String path, Watcher watcher) { while (true) { try { return super.exists(path, watcher); } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } @Override public byte[] getData(String path, boolean watch, Stat stat) { while (true) { try { return super.getData(path, watch, stat); } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } @Override public void delete(String path, int version) { while (true) { try { super.delete(path, version); return; } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } } (In the actual program there is much more logic and many more methods that I took out of the example for simplicity.) We can see that I'm using the same retry logic, but the arguments, method call, and return type are all different for each of the methods. Here's what I did to eliminate the duplication of code: public class BetterZooKeeper extends ZooKeeper { private void waitForReconnect() { // logic } @Override public Stat exists(final String path, final Watcher watcher) { return new RetryableZooKeeperAction<Stat>() { @Override public Stat action() { return BetterZooKeeper.super.exists(path, watcher); } }.run(); } @Override public byte[] getData(final String path, final boolean watch, final Stat stat) { return new RetryableZooKeeperAction<byte[]>() { @Override public byte[] action() { return BetterZooKeeper.super.getData(path, watch, stat); } }.run(); } @Override public void delete(final String path, final int version) { new RetryableZooKeeperAction<Object>() { @Override public Object action() { BetterZooKeeper.super.delete(path, version); return null; } }.run(); return; } private abstract class RetryableZooKeeperAction<T> { public abstract T action(); public final T run() { while (true) { try { return action(); } catch (KeeperException e) { // We will retry. } waitForReconnect(); } } } } The RetryableZooKeeperAction is parameterized with the return type of the function. The run() method holds the retry logic, and the action() method is a placeholder for whichever ZooKeeper method needs to be run. Each of the public methods of BetterZooKeeper instantiates an anonymous inner class that is a subclass of the RetryableZooKeeperAction inner class, and it overrides the action() method. The local variables are (strangely enough) implicitly passed to the action() method, which is possible because they are final. In the end, this approach does work and it does eliminate the duplication of the retry logic. However, it has two major drawbacks: (1) it creates a new object every time a method is called, and (2) it's ugly and hardly readable. Also I had to workaround the 'delete' method which has a void return value. So, here is my question: is there a better way to do this in Java? This can't be a totally uncommon task, and other languages (like Python) make it easier by allowing methods to be passed. I suspect there might be a way to do this through reflection, but I haven't been able to wrap my head around it.

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