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  • Where does this concept of "favor composition over inheritance" come from?

    - by Mason Wheeler
    In the last few months, the mantra "favor composition over inheritance" seems to have sprung up out of nowhere and become almost some sort of meme within the programming community. And every time I see it, I'm a little bit mystified. It's like someone said "favor drills over hammers." In my experience, composition and inheritance are two different tools with different use cases, and treating them as if they were interchangeable and one was inherently superior to the other makes no sense. Also, I never see a real explanation for why inheritance is bad and composition is good, which just makes me more suspicious. Is it supposed to just be accepted on faith? Liskov substitution and polymorphism have well-known, clear-cut benefits, and IMO comprise the entire point of using object-oriented programming, and no one ever explains why they should be discarded in favor of composition. Does anyone know where this concept comes from, and what the rationale behind it is?

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  • Public versus private inheritance when some of the parent's methods need to be exposed?

    - by Vorac
    Public inheritance means that all fields from the base class retain their declared visibility, while private means that they are forced to 'private' within the derived class's scope. What should be done if some of the parent's members (say, methods) need to be publicly exposed? I can think of two solution. Public inheritance somewhat breaks encapsulation. Furthermore, when you need to find out where is the method foo() defined, one needs to look at a chain of base classes. Private inheritance solves these problems, but introduces burden to write wrappers (more text). Which might be a good thing in the line of verbosity, but makes changes of interfaces incredibly cumbersome. What considerations am I missing? What constraints on the type of project are important? How to choose between the two (I am not even mentioning 'protected')? Note that I am targeting non-virtual methods. There isn't such a discussion for virtual methods (or is there).

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  • Virtual Win XP Mode stopped HP LJ Pro M1212nf MFP printing in Win 7 Pro

    - by Dee
    Virtual Win XP Mode stopped HP LJ Pro M1212nf MFP printing in Win 7 Pro: I am running Windows 7 Pro with Virtual Windows XP Mode. My printer is HP LaserJet Pro M1212nf MFP attached directly to a USB port of the computer. This printer was working fine in Windows 7, until I tried to attach the printer to the Virtual Windows XP Mode in order to load the printer driver in the Virtual Windows XP Mode. At that point, the printer disappeared from the list of USB devices on the toolbar at the top of the window of the Virtual Windows XP Mode. After installing the printer driver in the Virtual Windows XP Mode, the printer did not work in that mode and also no longer worked in Windows 7. In Windows 7 and in the Virtual Windows XP Mode, print files are sent to the print queue, but are never printed. In Windows 7, the print queue states that the printer is offline. In the Virtual Windows XP Mode, the printer can be toggled from "Print Offline" to "Print Online", but no print files are ever printed from the print queue. The printer acts as though it is no longer connected to the computer, even though it is still physically connected to the USB port of the computer. How can I get the printer to work again in Windows 7? (At this point, I am no longer interested in using the Virtual Windows XP Mode.) I have tried a large number of things to find and fix the printer problem, but have had no success. Device Manager cannot see the printer even though it is physically connected via USB port (have tried different USB ports) to the computer. Restoring Win 7 and Virtual Win XP Mode to times before the problem does not fix the problem. How can I get the computer to see the printer, so that I can print again in Win 7?

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  • Virtual Earth / Bing maps javascript file size

    - by Aquinas
    I am working with a site that uses virtual earth for its mapping. Unfortunately the file size of the referenced javascript file, ecn.dev.virtualearth.net/mapcontrol/mapcontrol.ashx?v=6.2, is 200 something kb before being expanded (to 970kb). As our site runs under https this file is not cached on the client, and can cause a few seconds delay to users, made more substantial in times of high load. My question is, is there anyway to get virtual earth to run smaller, or have more efficient lazy loading? At the moment it looks like our hands are tied.

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  • Implementation/interface inheritance design question.

    - by Neil G
    I would like to get the stackoverflow community's opinion on the following three design patterns. The first is implementation inheritance; the second is interface inheritance; the third is a middle ground. My specific question is: Which is best? implementation inheritance: class Base { X x() const = 0; void UpdateX(A a) { y_ = g(a); } Y y_; } class Derived: Base { X x() const { return f(y_); } } interface inheritance: class Base { X x() const = 0; void UpdateX(A a) = 0; } class Derived: Base { X x() const { return x_; } void UpdateX(A a) { x_ = f(g(a)); } X x_; } middle ground: class Base { X x() const { return x_; } void UpdateX(A a) = 0; X x_; } class Derived: Base { void UpdateX(A a) { x_ = f(g(a)); } } I know that many people prefer interface inheritance to implementation inheritance. However, the advantage of the latter is that with a pointer to Base, x() can be inlined and the address of x_ can be statically calculated.

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  • Question about Virtual Inheritance hierarchy

    - by Summer_More_More_Tea
    Hi there: I encounter this problem when tackling with virtual inheritance. I remember that in a non-virtual inheritance hierarchy, object of sub-class hold an object of its direct super-class. What about virtual inheritance? In this situation, does object of sub-class hold an object of its super-class directly or just hold a pointer pointing to an object of its super-class? By the way, why the output of the following code is: sizeof(A): 8 sizeof(B): 20 sizeof(C): 20 sizeof(C): 36 Code: #include <iostream> using namespace std; class A{ char k[ 3 ]; public: virtual void a(){}; }; class B : public virtual A{ char j[ 3 ]; public: virtual void b(){}; }; class C : public virtual B{ char i[ 3 ]; public: virtual void c(){}; }; class D : public B, public C{ char h[ 3 ]; public: virtual void d(){}; }; int main( int argc, char *argv[] ){ cout << "sizeof(A): " << sizeof( A ) << endl; cout << "sizeof(B): " << sizeof( B ) << endl; cout << "sizeof(C): " << sizeof( C ) << endl; cout << "sizeof(D): " << sizeof( D ) << endl; return 0; } Thanks in advance. Kind regards.

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  • Has inheritance become bad?

    - by mafutrct
    Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

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  • Is inheritance bad nowadays?

    - by mafutrct
    Personally, I think inheritance is a great tool, that, when applied reasonably, can greatly simplify code. However, I seems to me that many modern tools dislike inheritance. Let's take a simple example: Serialize a class to XML. As soon as inheritance is involved, this can easily turn into a mess. Especially if you're trying to serialize a derived class using the base class serializer. Sure, we can work around that. Something like a KnownType attribute and stuff. Besides being an itch in your code that you have to remember to update every time you add a derived class, that fails, too, if you receive a class from outside your scope that was not known at compile time. (Okay, in some cases you can still work around that, for instance using the NetDataContract serializer in .NET. Surely a certain advancement.) In any case, the basic principle still exists: Serialization and inheritance don't mix well. Considering the huge list of programming strategies that became possible and even common in the past decade, I feel tempted to say that inheritance should be avoided in areas that relate to serialization (in particular remoting and databases). Does that make sense? Or am messing things up? How do you handle inheritance and serialization?

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  • How do I install and use Windows Virtual PC in Windows 8?

    - by KronoS
    I really like the integrated Virtual Machine that Windows had built-in with Windows 7 with Windows Virtual PC. I'm looking to install that again. I'd like to be able to install multiple machines as I did before (XP, Ubuntu, Etc,.) but I can't seem to find Windows Virtual PC for Windows 8 any more. Is it still available?, and if not was there something setup in place to replace it? How do I use it? NOTE TO ALL: While this is an accepted self posted answer feel free to edit, comment, or add an answer of your own. If your answer is better than mine, I will accept. This question was a Super User Question of the Week. Read the blog entry for more details or contribute to the blog yourself

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  • Can i create a virtual machine on my laptop to be used with another monitor?

    - by Ranhiru
    OK, the scenario is like this... I have my laptop... and I have another user without a unit. He has only a keyboard, mouse and a monitor. Is there anyway that I can make him use my computer by creating a virtual environment which he will access, BUT, without interfering with my work. I use my laptop and view my OS from the laptop monitor. I create a virtual environment (some OS probably XP) and run it. The virtual environment is displayed in the connected monitor and the other user uses it using the extra keyboard/mouse and the monitor but without interfering my screen! Is this possible? Stupid? Futuristic? Need more hardware?

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  • SharePoint 2010 MSDN Labs

    - by Kelly Jones
    Eric Ligman, from Microsoft, posted a great blog post this week listing all of the SharePoint 2010 Virtual Labs that are available from Microsoft.  His blog entry is here: http://blogs.msdn.com/b/mssmallbiz/archive/2012/03/13/sharepoint-server-2010-msdn-virtual-labs-available-to-you-online-plus-more-sharepoint-2010-resources.aspx He also posted other resources as well. I’ve copied his Virtual Lab links here: SharePoint Server 2010 Virtual Labs MSDN Virtual Lab: SharePoint Server 2010: Introduction MSDN Virtual Lab: Getting Started with SharePoint 2010 MSDN Virtual Lab: SharePoint 2010 User Interface Advancements MSDN Virtual Lab: SharePoint Server 2010 Connectors & Using the Business Data Connectivity (BDC) Service MSDN Virtual Lab: SharePoint Server 2010: Advanced Search Security MSDN Virtual Lab: SharePoint Server 2010: Configuring Search UIs MSDN Virtual Lab: SharePoint Server 2010: Content Processing and Property Extraction MSDN Virtual Lab: SharePoint Server 2010: Developing a Custom Connector MSDN Virtual Lab: SharePoint Server 2010: Fast Search Web Crawler MSDN Virtual Lab: SharePoint Server 2010: Federated Search MSDN Virtual Lab: SharePoint Server 2010: Linguistics MSDN Virtual Lab: SharePoint Server 2010: People Search Administration and Management MSDN Virtual Lab: SharePoint Server 2010: Relevancy and Ranking MSDN Virtual Lab: Customizing MySites MSDN Virtual Lab: Designing Lists and Schemas MSDN Virtual Lab: Developing a BCS External Content Type with Visual Studio 2010 MSDN Virtual Lab: Developing a Sandboxed Solution with Web Parts MSDN Virtual Lab: Developing a Visual Web Part in Visual Studio 2010 MSDN Virtual Lab: Developing Business Intelligence Applications MSDN Virtual Lab: Enterprise Content Management MSDN Virtual Lab: LINQ to SharePoint 2010 MSDN Virtual Lab: Visual Studio SharePoint Tools MSDN Virtual Lab: Workflow In addition to the SharePoint Server 2010 Virtual Labs, here are a few other SharePoint 2010 resources that I thought you might also be interested in: Technical reference for Microsoft SharePoint Server 2010 SharePoint 2010: IT Pro Evaluation Guide Connecting SharePoint 2010 to Line-of-Business Systems to Deliver Business-Critical Solutions Configure SharePoint Server 2010 as a Single Server with Microsoft SQL Server: Test Lab Guide Microsoft SQL Server 2012 Reporting Services Add-in for Microsoft SharePoint Technologies 2010 Deploying FAST Search Server 2010 for SharePoint FAST Search Server 2010 for SharePoint Add or Remove an Index Column Upgrade worksheet for SharePoint Server 2010 Microsoft SharePoint Server 2010 Technical Library in Compiled Help format Microsoft SharePoint Foundation 2010 Technical Library in Compiled Help format Microsoft FAST Search Server 2010 for SharePoint Technical Library in Compiled Help format Microsoft Reseller partner Learning Path Microsoft solutions partners and ISVs Learning Path Microsoft partner Practice Accelerator for SharePoint Microsoft partner SharePoint 2010 Internal Use Licenses SharePoint Case Studies SharePoint MSDN Forums SharePoint TechNet Forums Microsoft SharePoint 2010 page on Microsoft Partner Network portal

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  • SQL SERVER – Retrieve and Explore Database Backup without Restoring Database – Idera virtual databas

    - by pinaldave
    I recently downloaded Idera’s SQL virtual database, and tested it. There are a few things about this tool which caught my attention. My Scenario It is quite common in real life that sometimes observing or retrieving older data is necessary; however, it had changed as time passed by. The full database backup was 40 GB in size, and, to restore it on our production server, it usually takes around 16 to 22 minutes, depending on the load server that is usually present. This range in time varies from one server to another as per the configuration of the computer. Some other issues we used to have are the following: When we try to restore a large 40-GB database, we needed at least that much space on our production server. Once in a while, we even had to make changes in the restored database, and use the said changed and restored database for our purpose, making it more time-consuming. My Solution I have heard a lot about the Idera’s SQL virtual database tool.. Well, right after we started to test this tool, we found out that it really delivers what it promises. Using this software was very easy and we were able to restore our database from backup in less than 2 minutes, sparing us from the usual longer time of 16–22 minutes. The needful was finished in a total of 10 minutes. Another interesting observation is that there is no need to have an additional space for restoring the database. For complete database restoration, the single additional MB on the drive is not required anymore. We can use the database in the same way as our regular database, and there is no need for any additional configuration and setup. Let us look at the most relevant points of this product based on my initial experience: Quick restoration of the database backup No additional space required for database restoration virtual database has no physical .MDF or .LDF The database which is restored is, in fact, the backup file converted in the virtual database. DDL and DML queries can be executed against this virtually restored database. Regular backup operation can be implemented against virtual database, creating a physical .bak file that can be used for future use. There was no observed degradation in performance on the original database as well the restored virtual database. Additional T-SQL queries can be let off on the virtual database. Well, this summarizes my quick review. And, as I was saying, I am very impressed with the product and I plan to explore it more. There are many features that I have noticed in this tool, which I think can be very useful if properly understood. I had taken a few screenshots using my demo database afterwards. Let us see what other things this tool can do besides the mentioned activities. I am surprised with its performance so I want to know how exactly this feature works, specifically in the matter of why it does not create any additional files and yet, it still allows update on the virtually restored database. I guess I will have to send an e-mail to the developers of Idera and try to figure this out from them. I think this tool is very useful, and it delivers a high level of performance way more than what I expected. Soon, I will write a review for additional uses of SQL virtual database.. If you are using SQL virtual database in your production environment, I am eager to learn more about it and your experience while using it. The ‘Virtual’ Part of virtual database When I set out to test this software, I thought virtual database had something to do with Hyper-V or visualization. In fact, the virtual database is a kind of database which shows up in your SQL Server Management Studio without actually restoring or even creating it. This tool creates a database in SSMS from the backup of the same database. The backup, however, works virtually the same way as original database. Potential Usage of virtual database: As soon as I described this tool to my teammate, I think his very first reaction was, “hey, if we have this then there is no need for log shipping.” I find his comment very interesting as log shipping is something where logs are moved to another server. In fact, there are no updates on the database from log; I would rather compare it with Snapshot Replication. In fact, whatever we use, snapshot replicated database can be similarly used and configured with virtual database. I totally believe that we can use it for reporting purpose. In fact, after this database was configured, I think the uses of this tool are unlimited. I will have to spend some more time studying it and will get back to you. Click on images to see larger images. virtual database Console Harddrive Space before virtual database Setup Attach Full Backup Screen Backup on Harddrive Attach Full Backup Screen with Settings virtual database Setup – less than 60 sec virtual database Setup – Online Harddrive Space after virtual database Setup Point in Time Recovery Option – Timeline View virtual database Summary No Performance Difference between Regular DB vs Virtual DB Please note that all SQL Server MVP gets free license of this software. Reference: Pinal Dave (http://blog.SQLAuthority.com), Idera (virtual database) Filed under: Database, Pinal Dave, SQL, SQL Add-On, SQL Authority, SQL Backup and Restore, SQL Data Storage, SQL Query, SQL Server, SQL Tips and Tricks, SQL Utility, SQLAuthority News, T SQL, Technology Tagged: Idera

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  • why does vb.net not support multiple inheritance?

    - by isolatedIterator
    I've seen some discussion on why c# does not implement multiple inheritance but very little as to why it isn't supported in vb. I understand that both c# and vb are compiled down to intermediary language and so they both need to share similar restrictions. The lack of multiple inheritance in VB seems to have been given as one reason for the lack of the feature in dot net. Does anyone know why VB doesn't support multiple inheritance? I'm hoping for a bit of history lesson and discussion on why this was never considered for VB.

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  • why does vb not support multiple inheritance?

    - by isolatedIterator
    I've seen some discussion on why c# does not implement multiple inheritance but very little as to why it isn't supported in vb. I understand that both c# and vb are compiled down to intermediary language and so they both need to share similar restrictions. The lack of multiple inheritance in VB seems to have been given as one reason for the lack of the feature in dot net. Does anyone know why VB doesn't support multiple inheritance? I'm hoping for a bit of history lesson and discussion on why this was never considered for VB.

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  • Composition vs Inheritance and GUI toolkits

    - by Anin Teger
    It's said that composition is preferred over inheritance. Every single open source GUI toolkit however uses inheritance for the drawn widgets (windows, labels, frames, buttons, etc). I checked Qt, wxWidgets, and GTK+. Is there an example of a GUI toolkit (written in any language) that uses composition instead of inheritance to separate the various widgets?

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  • Are Virtual-Desktop Managers good or bad for system resources?

    - by jasondavis
    I am looking at Virtual-Desktop Managers for Windows 7. Right now it seems that VirtualWin is supposed to be about the best one available for use on Windows. I have never used anything like this though and I am just curious from others experience and knowledge, does something like this hog up a lot of system resources? I do not NEED it but it is a nice feature to have when I do want to use it, my PC's performance is more important then using it. So is virtual esktop managers a resource hog or probably not? Please share any tips/advice/ or comments on them, thank you =)

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  • Windows Azure Virtual Machine Test Drive Kit

    - by Clint Edmonson
    The public preview of hosted Virtual Machines in Windows Azure is now available to the general public. This platform preview enables you to evaluate our new IaaS and Enterprise Networking capabilities. Once you have registered for the 90 Day Free Trial and created a new account, you can access the preview directly at this link: https://account.windowsazure.com/PreviewFeatures If you’ve been to any of my presentations lately, you’ll know that I’m fired up about these new offerings. As I’ve worked through some scenarios for myself and with my customers, I’ve been collecting the resources that helped me to ramp up. Here’s a collection of links to the items I’ve found most useful: Core Resources Digital Chalk Talk Videos – detailed technical overviews of the new Windows Azure services and supporting technologies as announced June 7, including Virtual Machines (IaaS Windows and Linux), Storage, Command Line Tools http://www.meetwindowsazure.com/DigitalChalkTalks Scenarios Videos on You Tube – “how to” guides, including “Create and Manage Virtual Networks”, “Create & Manage SQL Database”, and many more http://www.youtube.com/user/windowsazure Windows Azure Trust Center - provides a comprehensive of view of Windows Azure and security and compliance practices http://www.windowsazure.com/en-us/support/trust-center/ MSDN Forums for Windows Azure http://www.windowsazure.com/en-us/support/preview-support/ Microsoft Knowledge Base article Microsoft server software support for Windows Azure Virtual Machines Videos Deep Dive into Running Virtual Machines on Windows Azure Windows Azure Virtual Machines and Virtual Networks Windows Azure IaaS and How It Works Deep Dive into Windows Azure Virtual Machines: From the Cloud Vendor and Enterprise Perspective An Overview of Managing Applications, Services, and Virtual Machines in Windows Azure Monitoring and Managing Your Windows Azure Applications and Services Overview of Windows Azure Networking Features Hybrid Will Rule: Options to Connect, Extend and Integrate Applications in Your Data Center and Windows Azure Business Continuity in the Windows Azure Cloud Linux on Windows Azure Blogs Understanding Windows Azure Virtual Machines An Overview of Windows Azure Virtual Network Virtual Machines and Windows Running SQL Server in a Windows Azure Virtual Machine Support for Linux Virtual Machines on Windows Azure

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