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  • Membership in ASP.Net applications - part 3

    - by nikolaosk
    This is the third post in a series of posts regarding ASP.Net built in membership functionality,providers,controls. You can read the first one post one here . You can read the second post here . In this post I would like to investigate how to use the Membership class methods to achieve the same functionality we have with the login web server controls.The login web server controls live inside the .aspx pages and access the underlying abstract membership classes to perform the desired functionality...(read more)

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  • Using MVP, how to create a view from another view, linked with the same model object

    - by Dinaiz
    Background We use the Model-View-Presenter design pattern along with the abstract factory pattern and the "signal/slot" pattern in our application, to fullfill 2 main requirements Enhance testability (very lightweight GUI, every action can be simulated in unit tests) Make the "view" totally independant from the rest, so we can change the actual view implementation, without changing anything else In order to do so our code is divided in 4 layers : Core : which holds the model Presenter : which manages interactions between the view interfaces (see bellow) and the core View Interfaces : they define the signals and slots for a View, but not the implementation Views : the actual implementation of the views When the presenter creates or deals with views, it uses an abstract factory and only knows about the view interfaces. It does the signal/slot binding between views interfaces. It doesn't care about the actual implementation. In the "views" layer, we have a concrete factory which deals with implementations. The signal/slot mechanism is implemented using a custom framework built upon boost::function. Really, what we have is something like that : http://martinfowler.com/eaaDev/PassiveScreen.html Everything works fine. The problem However, there's a problem I don't know how to solve. Let's take for example a very simple drag and drop example. I have two ContainersViews (ContainerView1, ContainerView2). ContainerView1 has an ItemView1. I drag the ItemView1 from ContainerView1 to ContainerView2. ContainerView2 must create an ItemView2, of a different type, but which "points" to the same model object as ItemView1. So the ContainerView2 gets a callback called for the drop action with ItemView1 as a parameter. It calls ContainerPresenterB passing it ItemViewB In this case we are only dealing with views. In MVP-PV, views aren't supposed to know anything about the presenter nor the model, right ? How can I create the ItemView2 from the ItemView1, not knowing which model object is ItemView1 representing ? I thought about adding an "itemId" to every view, this id being the id of the core object the view represents. So in pseudo code, ContainerPresenter2 would do something like itemView2=abstractWidgetFactory.createItemView2(); this.add(itemView2,itemView1.getCoreObjectId()) I don't get too much into details. That just work. The problem I have here is that those itemIds are just like pointers. And pointers can be dangling. Imagine that by mistake, I delete itemView1, and this deletes coreObject1. The itemView2 will have a coreObjectId which represents an invalid coreObject. Isn't there a more elegant and "bulletproof" solution ? Even though I never did ObjectiveC or macOSX programming, I couldn't help but notice that our framework is very similar to Cocoa framework. How do they deal with this kind of problem ? Couldn't find more in-depth information about that on google. If someone could shed some light on this. I hope this question isn't too confusing ...

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  • Of C# Iterators and Performance

    - by James Michael Hare
    Some of you reading this will be wondering, "what is an iterator" and think I'm locked in the world of C++.  Nope, I'm talking C# iterators.  No, not enumerators, iterators.   So, for those of you who do not know what iterators are in C#, I will explain it in summary, and for those of you who know what iterators are but are curious of the performance impacts, I will explore that as well.   Iterators have been around for a bit now, and there are still a bunch of people who don't know what they are or what they do.  I don't know how many times at work I've had a code review on my code and have someone ask me, "what's that yield word do?"   Basically, this post came to me as I was writing some extension methods to extend IEnumerable<T> -- I'll post some of the fun ones in a later post.  Since I was filtering the resulting list down, I was using the standard C# iterator concept; but that got me wondering: what are the performance implications of using an iterator versus returning a new enumeration?   So, to begin, let's look at a couple of methods.  This is a new (albeit contrived) method called Every(...).  The goal of this method is to access and enumeration and return every nth item in the enumeration (including the first).  So Every(2) would return items 0, 2, 4, 6, etc.   Now, if you wanted to write this in the traditional way, you may come up with something like this:       public static IEnumerable<T> Every<T>(this IEnumerable<T> list, int interval)     {         List<T> newList = new List<T>();         int count = 0;           foreach (var i in list)         {             if ((count++ % interval) == 0)             {                 newList.Add(i);             }         }           return newList;     }     So basically this method takes any IEnumerable<T> and returns a new IEnumerable<T> that contains every nth item.  Pretty straight forward.   The problem?  Well, Every<T>(...) will construct a list containing every nth item whether or not you care.  What happens if you were searching this result for a certain item and find that item after five tries?  You would have generated the rest of the list for nothing.   Enter iterators.  This C# construct uses the yield keyword to effectively defer evaluation of the next item until it is asked for.  This can be very handy if the evaluation itself is expensive or if there's a fair chance you'll never want to fully evaluate a list.   We see this all the time in Linq, where many expressions are chained together to do complex processing on a list.  This would be very expensive if each of these expressions evaluated their entire possible result set on call.    Let's look at the same example function, this time using an iterator:       public static IEnumerable<T> Every<T>(this IEnumerable<T> list, int interval)     {         int count = 0;         foreach (var i in list)         {             if ((count++ % interval) == 0)             {                 yield return i;             }         }     }   Notice it does not create a new return value explicitly, the only evidence of a return is the "yield return" statement.  What this means is that when an item is requested from the enumeration, it will enter this method and evaluate until it either hits a yield return (in which case that item is returned) or until it exits the method or hits a yield break (in which case the iteration ends.   Behind the scenes, this is all done with a class that the CLR creates behind the scenes that keeps track of the state of the iteration, so that every time the next item is asked for, it finds that item and then updates the current position so it knows where to start at next time.   It doesn't seem like a big deal, does it?  But keep in mind the key point here: it only returns items as they are requested. Thus if there's a good chance you will only process a portion of the return list and/or if the evaluation of each item is expensive, an iterator may be of benefit.   This is especially true if you intend your methods to be chainable similar to the way Linq methods can be chained.    For example, perhaps you have a List<int> and you want to take every tenth one until you find one greater than 10.  We could write that as:       List<int> someList = new List<int>();         // fill list here         someList.Every(10).TakeWhile(i => i <= 10);     Now is the difference more apparent?  If we use the first form of Every that makes a copy of the list.  It's going to copy the entire list whether we will need those items or not, that can be costly!    With the iterator version, however, it will only take items from the list until it finds one that is > 10, at which point no further items in the list are evaluated.   So, sounds neat eh?  But what's the cost is what you're probably wondering.  So I ran some tests using the two forms of Every above on lists varying from 5 to 500,000 integers and tried various things.    Now, iteration isn't free.  If you are more likely than not to iterate the entire collection every time, iterator has some very slight overhead:   Copy vs Iterator on 100% of Collection (10,000 iterations) Collection Size Num Iterated Type Total ms 5 5 Copy 5 5 5 Iterator 5 50 50 Copy 28 50 50 Iterator 27 500 500 Copy 227 500 500 Iterator 247 5000 5000 Copy 2266 5000 5000 Iterator 2444 50,000 50,000 Copy 24,443 50,000 50,000 Iterator 24,719 500,000 500,000 Copy 250,024 500,000 500,000 Iterator 251,521   Notice that when iterating over the entire produced list, the times for the iterator are a little better for smaller lists, then getting just a slight bit worse for larger lists.  In reality, given the number of items and iterations, the result is near negligible, but just to show that iterators come at a price.  However, it should also be noted that the form of Every that returns a copy will have a left-over collection to garbage collect.   However, if we only partially evaluate less and less through the list, the savings start to show and make it well worth the overhead.  Let's look at what happens if you stop looking after 80% of the list:   Copy vs Iterator on 80% of Collection (10,000 iterations) Collection Size Num Iterated Type Total ms 5 4 Copy 5 5 4 Iterator 5 50 40 Copy 27 50 40 Iterator 23 500 400 Copy 215 500 400 Iterator 200 5000 4000 Copy 2099 5000 4000 Iterator 1962 50,000 40,000 Copy 22,385 50,000 40,000 Iterator 19,599 500,000 400,000 Copy 236,427 500,000 400,000 Iterator 196,010       Notice that the iterator form is now operating quite a bit faster.  But the savings really add up if you stop on average at 50% (which most searches would typically do):     Copy vs Iterator on 50% of Collection (10,000 iterations) Collection Size Num Iterated Type Total ms 5 2 Copy 5 5 2 Iterator 4 50 25 Copy 25 50 25 Iterator 16 500 250 Copy 188 500 250 Iterator 126 5000 2500 Copy 1854 5000 2500 Iterator 1226 50,000 25,000 Copy 19,839 50,000 25,000 Iterator 12,233 500,000 250,000 Copy 208,667 500,000 250,000 Iterator 122,336   Now we see that if we only expect to go on average 50% into the results, we tend to shave off around 40% of the time.  And this is only for one level deep.  If we are using this in a chain of query expressions it only adds to the savings.   So my recommendation?  If you have a resonable expectation that someone may only want to partially consume your enumerable result, I would always tend to favor an iterator.  The cost if they iterate the whole thing does not add much at all -- and if they consume only partially, you reap some really good performance gains.   Next time I'll discuss some of my favorite extensions I've created to make development life a little easier and maintainability a little better.

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  • April 2010 Meeting of Israel Dot Net Developers User Group (IDNDUG)

    - by Jackie Goldstein
    Note the special date of this meeting - Thursday April 29, 2010 The April 2010 meeting of the Israel Dot Net Developers User Group will be held on Thursday April 29, 2010 .   This meeting will focus on parallel programming – in general and the support in VS 2010.  Our speaker will be Asaf Shelly, a recognized expert in parallel programming. Abstract : (1) Parallel Programming in Microsoft's Environments. The fundamentals of Windows have always been parallel. Starting with message queues...(read more)

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  • The Data Scientist

    - by BuckWoody
    A new term - well, perhaps not that new - has come up and I’m actually very excited about it. The term is Data Scientist, and since it’s new, it’s fairly undefined. I’ll explain what I think it means, and why I’m excited about it. In general, I’ve found the term deals at its most basic with analyzing data. Of course, we all do that, and the term itself in that definition is redundant. There is no science that I know of that does not work with analyzing lots of data. But the term seems to refer to more than the common practices of looking at data visually, putting it in a spreadsheet or report, or even using simple coding to examine data sets. The term Data Scientist (as far as I can make out this early in it’s use) is someone who has a strong understanding of data sources, relevance (statistical and otherwise) and processing methods as well as front-end displays of large sets of complicated data. Some - but not all - Business Intelligence professionals have these skills. In other cases, senior developers, database architects or others fill these needs, but in my experience, many lack the strong mathematical skills needed to make these choices properly. I’ve divided the knowledge base for someone that would wear this title into three large segments. It remains to be seen if a given Data Scientist would be responsible for knowing all these areas or would specialize. There are pretty high requirements on the math side, specifically in graduate-degree level statistics, but in my experience a company will only have a few of these folks, so they are expected to know quite a bit in each of these areas. Persistence The first area is finding, cleaning and storing the data. In some cases, no cleaning is done prior to storage - it’s just identified and the cleansing is done in a later step. This area is where the professional would be able to tell if a particular data set should be stored in a Relational Database Management System (RDBMS), across a set of key/value pair storage (NoSQL) or in a file system like HDFS (part of the Hadoop landscape) or other methods. Or do you examine the stream of data without storing it in another system at all? This is an important decision - it’s a foundation choice that deals not only with a lot of expense of purchasing systems or even using Cloud Computing (PaaS, SaaS or IaaS) to source it, but also the skillsets and other resources needed to care and feed the system for a long time. The Data Scientist sets something into motion that will probably outlast his or her career at a company or organization. Often these choices are made by senior developers, database administrators or architects in a company. But sometimes each of these has a certain bias towards making a decision one way or another. The Data Scientist would examine these choices in light of the data itself, starting perhaps even before the business requirements are created. The business may not even be aware of all the strategic and tactical data sources that they have access to. Processing Once the decision is made to store the data, the next set of decisions are based around how to process the data. An RDBMS scales well to a certain level, and provides a high degree of ACID compliance as well as offering a well-known set-based language to work with this data. In other cases, scale should be spread among multiple nodes (as in the case of Hadoop landscapes or NoSQL offerings) or even across a Cloud provider like Windows Azure Table Storage. In fact, in many cases - most of the ones I’m dealing with lately - the data should be split among multiple types of processing environments. This is a newer idea. Many data professionals simply pick a methodology (RDBMS with Star Schemas, NoSQL, etc.) and put all data there, regardless of its shape, processing needs and so on. A Data Scientist is familiar not only with the various processing methods, but how they work, so that they can choose the right one for a given need. This is a huge time commitment, hence the need for a dedicated title like this one. Presentation This is where the need for a Data Scientist is most often already being filled, sometimes with more or less success. The latest Business Intelligence systems are quite good at allowing you to create amazing graphics - but it’s the data behind the graphics that are the most important component of truly effective displays. This is where the mathematics requirement of the Data Scientist title is the most unforgiving. In fact, someone without a good foundation in statistics is not a good candidate for creating reports. Even a basic level of statistics can be dangerous. Anyone who works in analyzing data will tell you that there are multiple errors possible when data just seems right - and basic statistics bears out that you’re on the right track - that are only solvable when you understanding why the statistical formula works the way it does. And there are lots of ways of presenting data. Sometimes all you need is a “yes” or “no” answer that can only come after heavy analysis work. In that case, a simple e-mail might be all the reporting you need. In others, complex relationships and multiple components require a deep understanding of the various graphical methods of presenting data. Knowing which kind of chart, color, graphic or shape conveys a particular datum best is essential knowledge for the Data Scientist. Why I’m excited I love this area of study. I like math, stats, and computing technologies, but it goes beyond that. I love what data can do - how it can help an organization. I’ve been fortunate enough in my professional career these past two decades to work with lots of folks who perform this role at companies from aerospace to medical firms, from manufacturing to retail. Interestingly, the size of the company really isn’t germane here. I worked with one very small bio-tech (cryogenics) company that worked deeply with analysis of complex interrelated data. So  watch this space. No, I’m not leaving Azure or distributed computing or Microsoft. In fact, I think I’m perfectly situated to investigate this role further. We have a huge set of tools, from RDBMS to Hadoop to allow me to explore. And I’m happy to share what I learn along the way.

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  • Donald Belcham&rsquo;s Brownfield Workshop in Winnipeg July 23!

    - by D'Arcy Lussier
    Donald Belcham delivered his “Making the Most of Brownfield Application Development” workshop to rave reviews at the Prairie Developer Conference in Regina. I’m excited to announce that Donald will be delivering his workshop in Winnipeg on Friday, July 23rd! Pricing for the event is $149.99 before July 2nd, and $199.99 after and up to the event date. For more information including workshop abstract and how to register, check out the event info page here.

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  • Speaking in Raleigh NC June 15th

    - by Andrew Kelly
    Just a heads up to those in the area that I will be speaking at the (TriPASS) Raleigh SQL Server user group on the 15th of June 2010. The topic is Storage & I/O Best Practices. The abstract is listed below: SQL Server relies heavily on a well configured storage sub-system to perform at its peak but unfortunately this is one of the most neglected or mis-configured areas of a SQL Server instance. Here we will focus on the best practices related to how SQL Server works with the underlying storage...(read more)

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  • Presenting Designing an SSIS Execution Framework to Steel City SQL 18 Jan 2011!

    - by andyleonard
    I'm honored to present Designing an SSIS Execution Framework (Level 300) to Steel City SQL - the Birmingham Alabama chapter of PASS - on 18 Jan 2011! The meeting starts at 6:00 PM 18 Jan 2011 and will be held at: New Horizons Computer Learning Center 601 Beacon Pkwy. West Suite 106 Birmingham, Alabama, 35209 ( Map for directions ) Abstract In this “demo-tastic” presentation, SSIS trainer, author, and consultant Andy Leonard explains the what, why, and how of an SSIS framework that delivers metadata-driven...(read more)

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  • SQL Saturday Birmingham #328 Database Design Precon In One Week

    - by drsql
    On September 22, I will be doing my "How to Design a Relational Database" pre-conference session in Birmingham, Alabama. You can see the abstract here if you are interested, and you can sign up there too, naturally. At just $100, which includes a free ebook copy of my database design book, it is a great bargain and I totally promise it will be a little over 7 hours of talking about and designing databases, which will certainly be better than what you do on a normal work day, even a Friday....(read more)

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  • March 2010 Meeting of Israel Dot Net Developers User Group (IDNDUG)

    - by Jackie Goldstein
    Note the special date of this meeting - Wednesday March 24, 2010 For our March 2010 meeting of the Israel Dot Net Developers User Group we have the opportunity for a special meeting with Brad Abrams from Microsoft Corp, who will in Israel for the Developer Academy 4 event. Our user group meeting will be held on Wednesday March 24, 2010 .   This meeting will focus on building Line of Business applications with Silverlight 4, RIA Services and VS2010. Abstract: Building Business Applications...(read more)

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  • The Template Method Design Pattern using C# .Net

    - by nijhawan.saurabh
    First of all I'll just put this pattern in context and describe its intent as in the GOF book:   Template Method: Define the skeleton of an algorithm in an operation, deferring some steps to Subclasses. Template Method lets subclasses redefine certain steps of an algorithm without changing the Algorithm's Structure.    Usage: When you are certain about the High Level steps involved in an Algorithm/Work flow you can use the Template Pattern which allows the Base Class to define the Sequence of the Steps but permits the Sub classes to alter the implementation of any/all steps.   Example in the .Net framework: The most common example is the Asp.Net Page Life Cycle. The Page Life Cycle has a few methods which are called in a sequence but we have the liberty to modify the functionality of any of the methods by overriding them.   Sample implementation of Template Method Pattern:   Let's see the class diagram first:            Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:8.0pt; mso-para-margin-left:0in; line-height:107%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-font-kerning:1.0pt; mso-ligatures:standard;}   And here goes the code:EmailBase.cs     1 using System;     2 using System.Collections.Generic;     3 using System.Linq;     4 using System.Text;     5 using System.Threading.Tasks;     6      7 namespace TemplateMethod     8 {     9     public abstract class EmailBase    10     {    11     12         public bool SendEmail()    13         {    14             if (CheckEmailAddress() == true) // Method1 in the sequence    15             {    16                 if (ValidateMessage() == true) // Method2 in the sequence    17                 {    18                     if (SendMail() == true) // Method3 in the sequence    19                     {    20                         return true;    21                     }    22                     else    23                     {    24                         return false;    25                     }    26     27                 }    28                 else    29                 {    30                     return false;    31                 }    32     33             }    34             else    35             {    36                 return false;    37     38             }    39     40     41         }    42     43         protected abstract bool CheckEmailAddress();    44         protected abstract bool ValidateMessage();    45         protected abstract bool SendMail();    46     47     48     }    49 }    50    EmailYahoo.cs      1 using System;     2 using System.Collections.Generic;     3 using System.Linq;     4 using System.Text;     5 using System.Threading.Tasks;     6      7 namespace TemplateMethod     8 {     9     public class EmailYahoo:EmailBase    10     {    11     12         protected override bool CheckEmailAddress()    13         {    14             Console.WriteLine("Checking Email Address : YahooEmail");    15             return true;    16         }    17         protected override bool ValidateMessage()    18         {    19             Console.WriteLine("Validating Email Message : YahooEmail");    20             return true;    21         }    22     23     24         protected override bool SendMail()    25         {    26             Console.WriteLine("Semding Email : YahooEmail");    27             return true;    28         }    29     30     31     }    32 }    33   EmailGoogle.cs      1 using System;     2 using System.Collections.Generic;     3 using System.Linq;     4 using System.Text;     5 using System.Threading.Tasks;     6      7 namespace TemplateMethod     8 {     9     public class EmailGoogle:EmailBase    10     {    11     12         protected override bool CheckEmailAddress()    13         {    14             Console.WriteLine("Checking Email Address : GoogleEmail");    15             return true;    16         }    17         protected override bool ValidateMessage()    18         {    19             Console.WriteLine("Validating Email Message : GoogleEmail");    20             return true;    21         }    22     23     24         protected override bool SendMail()    25         {    26             Console.WriteLine("Semding Email : GoogleEmail");    27             return true;    28         }    29     30     31     }    32 }    33   Program.cs      1 using System;     2 using System.Collections.Generic;     3 using System.Linq;     4 using System.Text;     5 using System.Threading.Tasks;     6      7 namespace TemplateMethod     8 {     9     class Program    10     {    11         static void Main(string[] args)    12         {    13             Console.WriteLine("Please choose an Email Account to send an Email:");    14             Console.WriteLine("Choose 1 for Google");    15             Console.WriteLine("Choose 2 for Yahoo");    16             string choice = Console.ReadLine();    17     18             if (choice == "1")    19             {    20                 EmailBase email = new EmailGoogle(); // Rather than newing it up here, you may use a factory to do so.    21                 email.SendEmail();    22     23             }    24             if (choice == "2")    25             {    26                 EmailBase email = new EmailYahoo(); // Rather than newing it up here, you may use a factory to do so.    27                 email.SendEmail();    28             }    29         }    30     }    31 }    32    Final Words: It's very obvious that why the Template Method Pattern is a popular pattern, everything at last revolves around Algorithms and if you are clear with the steps involved it makes real sense to delegate the duty of implementing the step's functionality to the sub classes. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:8.0pt; mso-para-margin-left:0in; line-height:107%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-font-kerning:1.0pt; mso-ligatures:standard;}

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  • Teacher demands excessive/unjustified use of Design Patterns

    - by SoboLAN
    I study computer science and I have a class called "Programming Techniques". Its purpose is to teach (us) good object oriented design principles. During the semester we have homeworks, programs that we must write to demonstrate what we've learned. The lab assistant demands for each of these homeworks that specific design patterns should be used. For example, the current homework is an application used for processing customer orders. We are demanded to use either "Factory Method" or "Abstract Factory" design patterns for this. It gets even worse: at the end of the semester we must write a program (something more complex) that must use at least one creational pattern, at least one structural pattern and at least one behavioural pattern. Is it normal to demand this ? I mean, forcing us to design our programs in such a way that a specific design pattern makes sense is just beyond what I consider ok. If I'm a car mechanic and have a huge tool box, then I will use a certain tool from that box if and when the situation demands it. Not more, not less. If my design of the application doesn't demand at all the use of "Abstract Factory" (for example), then why should I implement it ? I'm not sure yet if the senior lecturer agrees with what the lab assistant is demanding, but I want to talk to him about it and I need solid arguments to do so. How should I approach this problem with him ? PS: I'm sure there must be a better way to teach us these things. Maybe making us each week read about 3 design patterns and the next week giving us a test with small but specific programming or architectural situations/problems. The goal in that test would be to identify what design patterns would make sense and how they could be implemented. This way, he can see if we understand them. EDIT: These homeworks are not just 100-line programs, they have quite a lot of requirements and are fairly complicated. This is the reason we have about 2 - 3 weeks of deadline for each of them. I agree that practicing this is the best way to learn. But shouldn't smaller programs/applications be used for this ? Something just for demonstrating purposes. Not big programs with lots of requirements/classes/etc.

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  • Are there any memorization techniques that exist for programmers? [closed]

    - by Akromyk
    I just watched this video on Ted.com entitled: Joshua Foer: Feats of memory anyone can do and it got me thinking about memory from a programmers perspective. There are so many abstract concepts and syntactic nuances we encounter daily, and yet we still manage to remember enough information to be productive. The memory palace may help in remembering someone's name or a random story but are there any memorization techniques that can better aid programmers?

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  • What simple game is good to learn OO principles?

    - by Bogdan Gavril
    I have to come up with a project propsal for my students, here are some details: The design should be gove over OO concepts: encapsulation, interfaces, inheritance, abstract classes Idealy a game, to keep interest high No GUI, just the console Effective time to finish this: ~ 6 days (1 person per proj) I have found one nice example of a game with carnivore and herbivore cells in a drop of water (array), it's a game of life twist. It is a bit too simple. Any ideeas? Aditional info: - language is C#

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  • GoF Design Patterns - which ones do you actually use?

    - by CraigS
    I'm trying to educate my colleagues in the area of design patterns. Some of the original Gang of Four patterns are a little esoteric, so I'm wondering if there is a sub-group of "essential" patterns that all programmers should know. As I look through the list, I think I've probably used - Abstract Factory Factory Method Singleton Bridge Facade Command Which ones do you actually use in practice, and what do you use them for? Link for those wanting a list of patterns

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  • Checking who is connected to your server, with PowerShell.

    - by Fatherjack
    There are many occasions when, as a DBA, you want to see who is connected to your SQL Server, along with how they are connecting and what sort of activities they are carrying out. I’m going to look at a couple of ways of getting this information and compare the effort required and the results achieved of each. SQL Server comes with a couple of stored procedures to help with this sort of task – sp_who and its undocumented counterpart sp_who2. There is also the pumped up version of these called sp_whoisactive, written by Adam Machanic which does way more than these procedures. I wholly recommend you try it out if you don’t already know how it works. When it comes to serious interrogation of your SQL Server activity then it is absolutely indispensable. Anyway, back to the point of this blog, we are going to look at getting the information from sp_who2 for a remote server. I wrote this Powershell script a week or so ago and was quietly happy with it for a while. I’m relatively new to Powershell so forgive both my rather low threshold for entertainment and the fact that something so simple is a moderate achievement for me. $Server = 'SERVERNAME' $SMOServer = New-Object Microsoft.SQLServer.Management.SMO.Server $Server # connection and query stuff         $ConnectionStr = "Server=$Server;Database=Master;Integrated Security=True" $Query = "EXEC sp_who2" $Connection = new-object system.Data.SQLClient.SQLConnection $Table = new-object "System.Data.DataTable" $Connection.connectionstring = $ConnectionStr try{ $Connection.open() $Command = $Connection.CreateCommand() $Command.commandtext = $Query $result = $Command.ExecuteReader() $Table.Load($result) } catch{ # Show error $error[0] | format-list -Force } $Title = "Data access processes (" + $Table.Rows.Count + ")" $Table | Out-GridView -Title $Title $Connection.close() So this is pretty straightforward, create an SMO object that represents our chosen server, define a connection to the database and a table object for the results when we get them, execute our query over the connection, load the results into our table object and then, if everything is error free display these results to the PowerShell grid viewer. The query simply gets the results of ‘EXEC sp_who2′ for us. Depending on how many connections there are will influence how long the query runs. The grid viewer lets me sort and search the results so it can be a pretty handy way to locate troublesome connections. Like I say, I was quite pleased with this, it seems a pretty simple script and was working well for me, I have added a few parameters to control the output and give me more specific details but then I see a script that uses the $SMOServer object itself to provide the process information and saves having to define the connection object and query specifications. $Server = 'SERVERNAME' $SMOServer = New-Object Microsoft.SQLServer.Management.SMO.Server $Server $Processes = $SMOServer.EnumProcesses() $Title = "SMO processes (" + $Processes.Rows.Count + ")" $Processes | Out-GridView -Title $Title Create the SMO object of our server and then call the EnumProcesses method to get all the process information from the server. Staggeringly simple! The results are a little different though. Some columns are the same and we can see the same basic information so my first thought was to which runs faster – so that I can get my results more quickly and also so that I place less stress on my server(s). PowerShell comes with a great way of testing this – the Measure-Command function. All you have to do is wrap your piece of code in Measure-Command {[your code here]} and it will spit out the time taken to execute the code. So, I placed both of the above methods of getting SQL Server process connections in two Measure-Command wrappers and pressed F5! The Powershell console goes blank for a while as the code is executed internally when Measure-Command is used but the grid viewer windows appear and the console shows this. You can take the output from Measure-Command and format it for easier reading but in a simple comparison like this we can simply cross refer the TotalMilliseconds values from the two result sets to see how the two methods performed. The query execution method (running EXEC sp_who2 ) is the first set of timings and the SMO EnumProcesses is the second. I have run these on a variety of servers and while the results vary from execution to execution I have never seen the SMO version slower than the other. The difference has varied and the time for both has ranged from sub-second as we see above to almost 5 seconds on other systems. This difference, I would suggest is partly due to the cost overhead of having to construct the data connection and so on where as the SMO EnumProcesses method has the connection to the server already in place and just needs to call back the process information. There is also the difference in the data sets to consider. Let’s take a look at what we get and where the two methods differ Query execution method (sp_who2) SMO EnumProcesses Description - Urn What looks like an XML or JSON representation of the server name and the process ID SPID Spid The process ID Status Status The status of the process Login Login The login name of the user executing the command HostName Host The name of the computer where the  process originated BlkBy BlockingSpid The SPID of a process that is blocking this one DBName Database The database that this process is connected to Command Command The type of command that is executing CPUTime Cpu The CPU activity related to this process DiskIO - The Disk IO activity related to this process LastBatch - The time the last batch was executed from this process. ProgramName Program The application that is facilitating the process connection to the SQL Server. SPID1 - In my experience this is always the same value as SPID. REQUESTID - In my experience this is always 0 - Name In my experience this is always the same value as SPID and so could be seen as analogous to SPID1 from sp_who2 - MemUsage An indication of the memory used by this process but I don’t know what it is measured in (bytes, Kb, Mb…) - IsSystem True or False depending on whether the process is internal to the SQL Server instance or has been created by an external connection requesting data. - ExecutionContextID In my experience this is always 0 so could be analogous to REQUESTID from sp_who2. Please note, these are my own very brief descriptions of these columns, detail can be found from MSDN for columns in the sp_who results here http://msdn.microsoft.com/en-GB/library/ms174313.aspx. Where the columns are common then I would use that description, in other cases then the information returned is purely for interpretation by the reader. Rather annoyingly both result sets have useful information that the other doesn’t. sp_who2 returns Disk IO and LastBatch information which is really useful but the SMO processes method give you IsSystem and MemUsage which have their place in fault diagnosis methods too. So which is better? On reflection I think I prefer to use the sp_who2 method primarily but knowing that the SMO Enumprocesses method is there when I need it is really useful and I’m sure I’ll use it regularly. I’m OK with the fact that it is the slower method because Measure-Command has shown me how close it is to the other option and that it really isn’t a large enough margin to matter.

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  • Speaking this week at Richmond SQL Server User Group

    - by drsql
    Thursday night, at 6:00 (or so) I will be speaking in Richmond ( http://richmondsql.org/cs2007/ ), talking about How to Implement a Hierarchy using SQL Server. The abstract is: One of the most common structures you will come across in the real world is a hierarchy (either a single parent "tree" or a multi-parent "graph"). Many systems will implement the obvious examples, such as a corporate managerial structure or a bill of materials. It turns out that almost any many-to-many relationship can be...(read more)

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  • Design pattern to handle queries using multiple models

    - by coderkane
    I am presented with a dilemma while trying to re-designing the class structure for my PHP/MySQL application to make it more elegant and conform it to the SOLID principle. The problem goes like this: Let as assume, there is an abstract class called person which has certain properties to define a generic person, such as name, age, date of birth etc. There are two classes, student, and teacher, that implements this abstract class. They add their own unique properties to it. I have designed all the three classes to include all the operational logic (details of which are not relevant in context of the question). Now, I need to create views/reports/data grids which contain details from multiple classes, for example, say, a list of all students doing projects in Chemistry mentored by a teacher whose name is the parameter to the query. This is just one example of a view, there are many different views in the application, which uses data from 3-4 tables, and each of them have multiple input parameters to generate them. Considering this particular example, I have written the relevant query using JOIN and the results are as expected and proper, now here is the dilemma: Keeping in mind the single responsibility principle, where should I keep this query? It does not belong to either Student class, or Teacher class or any other classes currently present. a) Should I create a new class, say dataView class, and design it as a MVC pattern and keep the query there? What about the other views? how do they fit in this architecture? b) Should I not keep the query in code at all, and make it DB View ? c) Am I completely wrong in the approach? If so what is the right approach? My considerations are as follows: a) should be easy to add new views later on if requirement comes, without having to copy-paste-modify code b) would like to make it as loosely coupled as possible so that if minor db structure changes happen, it does not break I did google searches on report design and OOP report generators, but all the result seem to focus on the visual design of the report rather than fetching the data. I have already taken care of the visual aspect of the report using MVC with html templates. I am sure this is a very fundamental problem with known solution, but I am somehow not able to find it (maybe searching with wrong keyword). Edit1: Modified the title to make it more relevant Edit2: The accepted answer got me thinking in the right direction and identify my design flaws, which eventually led me to find this question and the solution in Stack Overflow which gave me the detailed answer to clear the confusion.

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  • New Book: "Systems Performance: Enterprise and the Cloud"

    - by uwes
    Brendan Gregg, former Solaris kernel engineer at Sun published his new book "Systems Performance: Enterprise and the Cloud" in October. The book is a modern, very comprehensive guide to general system performance principles and practices, as well as a highly detailed reference for specific UNIX and Linux observability tools used to examine and diagnose operating system behaviour. Read a more detailed abstract and review on Harry J Foxwell's Blog entry "Brendan Gregg's "Systems Performance: Enterprise and the Cloud"

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  • Confusion about inheritance

    - by Samuel Adam
    I know I might get downvoted for this, but I'm really curious. I was taught that inheritance is a very powerful polymorphism tool, but I can't seem to use it well in real cases. So far, I can only use inheritance when the base class is an abstract class. Examples : If we're talking about Product and Inventory, I quickly assumed that a Product is an Inventory because a Product must be inventorized as well. But a problem occured when user wanted to sell their Inventory item. It just doesn't seem to be right to change an Inventory object to it's subtype (Product), it's almost like trying to convert a parent to it's child. Another case is Customer and Member. It is logical (at least for me) to think that a Member is a Customer with some more privileges. Same problem occurred when user wanted to upgrade an existing Customer to become a Member. A very trivial case is the Employee case. Where Manager, Clerk, etc can be derived from Employee. Still, the same upgrading issue. I tried to use composition instead for some cases, but I really wanted to know if I'm missing something for inheritance solution here. My composition solution for those cases : Create a reference of Inventory inside a Product. Here I'm making an assumption about that Product and Inventory is talking in a different context. While Product is in the context of sales (price, volume, discount, etc), Inventory is in the context of physical management (stock, movement, etc). Make a reference of Membership instead inside Customer class instead of previous inheritance solution. Therefor upgrading a Customer is only about instantiating the Customer's Membership property. This example is keep being taught in basic programming classes, but I think it's more proper to have those Manager, Clerk, etc derived from an abstract Role class and make it a property in Employee. I found it difficult to find an example of a concrete class deriving from another concrete class. Is there any inheritance solution in which I can solve those cases? Being new in this OOP thing, I really really need a guidance. Thanks!

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  • Need help starting with DSL for charts/graphs

    - by Rex M
    I am unaware of any established work into Domain Specific Languages for describing charts / graphs. I am looking for specific answers of "yes, something like that exists (here)". To help be clear, in case I am possibly using the wrong verbiage to describe it, to me a DSL for charts would most certainly include: A grammar for describing the shape of an expected data set A grammar for describing a pipeline of behaviors that render an output Abstract / high-level enough to be mappable to most tool-specific grammars, such as Excel, Highchart, matplotlib, etc.

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  • Useful links

    - by Madhan ayyasamy
    Difference between STI vs Polymorphic associationsSTI vs PolymorphicDifference between habtm vs has_many :throughhabtm vs throughCapistrano Guide linkCapistrano guideRails application without database stuffclass Car < ActiveRecord::Baseself.abstract = trueendAnother link: rails without databaseNamed scope useful linkNamed scopeDifference between http and https verbhttp vs httpsRails 2.3 useful guide websiterails 2.3 guide

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  • 2010 Chicago Code Coming In May

    - by Tim Murphy
    The Lake Count .NET User Group is putting on it’s second Chicago Code Camp on May 1st.  I would encourage everyone to come out and participate in the Chicago area .NET community.  You can register here.  Better yet come of with a presentation of your own.  I have submitted an abstract for a presentation on Office Open XML. del.icio.us Tags: Chicago Code Camp,presentations,Office Open XML,LCNUG

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  • COLLABORATE 13 Call for Papers

    - by Marc Weintraub
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 Attention PeopleSoft customers!  Speak at the largest user-led PeopleSoft conference of the year and attend for free! Interested in submitting a presentation for COLLABORATE 13? October 12 is the deadline to submit your abstract. The COLLABORATE 13- Quest forum is your home for high-level education sessions around PeopleSoft. Presenting doesn’t just mean giving a solo lecture: you can present with a vendor, give a demonstration (internet will be provided), facilitate a hot topic discussion or even offer best practices from an experience your company has been through. Remember, to submit an abstract now, all you need is a short description of your presentation. Think you don't have a story to tell? Think again! Check out the COLLABORATE 13- Quest forum now to better understand what we are looking for. A selection committee of other PeopleSoft users will review all sessions and select the most relevant, customer-focused sessions possible to make COLLABORATE a great learning experience for everyone. Don't forget, one speaker from each session selected will be eligible to receive a complimentary registration to the entire event *some rules apply. Also, don’t forget to include your functional counterpart. The selection committee is looking to increase the amount of functional users attending and want to help them glean the most out of the event. Thank you for your time and please let the selection committee know if you have any questions about submitting a presentation. We look forward to seeing you at COLLABORATE 13 in Denver! Quest's COLLABORATE '13 website - http://www.questdirect.org/collaborate /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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  • Kernel module implementation estimate

    - by Ivan Teterevkov
    I have a very abstract question about a kernel module writing estimate. How much dev-hours/months may required to write or, especially, port an existant kernel driver for a new PCI HBA from one operating system to another (with different kernel API)? I am porting an already written kernel module for 82599 for Linux kernel to OS X's IOKit and try to get a working alpha. I can't imagine for how long this task may expand in time.

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