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  • Virtual Brown Bag Recap: JB's New Gem, Patterns 101, Killing VS, CodeMav

    - by Brian Schroer
    At this week's Virtual Brown Bag meeting: JB showed off his new SpeakerRate Ruby gem Claudio alerted us to the Refactoring Manifesto We answered the question "How do I get started with Design Patterns?" Ever had to kill a frozen instance of Visual Studio? Yeah, I thought so. Claudio showed us how to do it with PowerShell. (It's faster) JB previewed his new CodeMav web site, which will be a social network for developers (integration with Speaker Rate, slide share, github, StackOverflow, etc.) For detailed notes, links, and the video recording, go to the VBB wiki page: https://sites.google.com/site/vbbwiki/main_page/2011-01-06

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  • Liskov Substitution Principle and the Oft Forgot Third Wheel

    - by Stacy Vicknair
    Liskov Substitution Principle (LSP) is a principle of object oriented programming that many might be familiar with from the SOLID principles mnemonic from Uncle Bob Martin. The principle highlights the relationship between a type and its subtypes, and, according to Wikipedia, is defined by Barbara Liskov and Jeanette Wing as the following principle:   Let be a property provable about objects of type . Then should be provable for objects of type where is a subtype of .   Rectangles gonna rectangulate The iconic example of this principle is illustrated with the relationship between a rectangle and a square. Let’s say we have a class named Rectangle that had a property to set width and a property to set its height. 1: Public Class Rectangle 2: Overridable Property Width As Integer 3: Overridable Property Height As Integer 4: End Class   We all at some point here that inheritance mocks an “IS A” relationship, and by gosh we all know square IS A rectangle. So let’s make a square class that inherits from rectangle. However, squares do maintain the same length on every side, so let’s override and add that behavior. 1: Public Class Square 2: Inherits Rectangle 3:  4: Private _sideLength As Integer 5:  6: Public Overrides Property Width As Integer 7: Get 8: Return _sideLength 9: End Get 10: Set(value As Integer) 11: _sideLength = value 12: End Set 13: End Property 14:  15: Public Overrides Property Height As Integer 16: Get 17: Return _sideLength 18: End Get 19: Set(value As Integer) 20: _sideLength = value 21: End Set 22: End Property 23: End Class   Now, say we had the following test: 1: Public Sub SetHeight_DoesNotAffectWidth(rectangle As Rectangle) 2: 'arrange 3: Dim expectedWidth = 4 4: rectangle.Width = 4 5:  6: 'act 7: rectangle.Height = 7 8:  9: 'assert 10: Assert.AreEqual(expectedWidth, rectangle.Width) 11: End Sub   If we pass in a rectangle, this test passes just fine. What if we pass in a square?   This is where we see the violation of Liskov’s Principle! A square might "IS A” to a rectangle, but we have differing expectations on how a rectangle should function than how a square should! Great expectations Here’s where we pat ourselves on the back and take a victory lap around the office and tell everyone about how we understand LSP like a boss. And all is good… until we start trying to apply it to our work. If I can’t even change functionality on a simple setter without breaking the expectations on a parent class, what can I do with subtyping? Did Liskov just tell me to never touch subtyping again? The short answer: NO, SHE DIDN’T. When I first learned LSP, and from those I’ve talked with as well, I overlooked a very important but not appropriately stressed quality of the principle: our expectations. Our inclination is to want a logical catch-all, where we can easily apply this principle and wipe our hands, drop the mic and exit stage left. That’s not the case because in every different programming scenario, our expectations of the parent class or type will be different. We have to set reasonable expectations on the behaviors that we expect out of the parent, then make sure that those expectations are met by the child. Any expectations not explicitly expected of the parent aren’t expected of the child either, and don’t register as a violation of LSP that prevents implementation. You can see the flexibility mentioned in the Wikipedia article itself: A typical example that violates LSP is a Square class that derives from a Rectangle class, assuming getter and setter methods exist for both width and height. The Square class always assumes that the width is equal with the height. If a Square object is used in a context where a Rectangle is expected, unexpected behavior may occur because the dimensions of a Square cannot (or rather should not) be modified independently. This problem cannot be easily fixed: if we can modify the setter methods in the Square class so that they preserve the Square invariant (i.e., keep the dimensions equal), then these methods will weaken (violate) the postconditions for the Rectangle setters, which state that dimensions can be modified independently. Violations of LSP, like this one, may or may not be a problem in practice, depending on the postconditions or invariants that are actually expected by the code that uses classes violating LSP. Mutability is a key issue here. If Square and Rectangle had only getter methods (i.e., they were immutable objects), then no violation of LSP could occur. What this means is that the above situation with a rectangle and a square can be acceptable if we do not have the expectation for width to leave height unaffected, or vice-versa, in our application. Conclusion – the oft forgot third wheel Liskov Substitution Principle is meant to act as a guidance and warn us against unexpected behaviors. Objects can be stateful and as a result we can end up with unexpected situations if we don’t code carefully. Specifically when subclassing, make sure that the subclass meets the expectations held to its parent. Don’t let LSP think you cannot deviate from the behaviors of the parent, but understand that LSP is meant to highlight the importance of not only the parent and the child class, but also of the expectations WE set for the parent class and the necessity of meeting those expectations in order to help prevent sticky situations.   Code examples, in both VB and C# Technorati Tags: LSV,Liskov Substitution Principle,Uncle Bob,Robert Martin,Barbara Liskov,Liskov

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  • Silverlight Cream for April 24, 2010 -- #846

    - by Dave Campbell
    In this Issue: Michael Washington, Timmy Kokke, Pete Brown, Paul Yanez, Emil Stoychev, Jeremy Likness, and Pavan Podila. Shoutouts: If you've got some time to spend, the User Experience Kit is packed with info: User Experience Kit, and just plain fun to navigate ... thanks Scott Barnes for reminding me about it! Jesse Liberty is looking for some help organizing and cataloging posts for a new project he's got going: Help Wanted Emil Stoychev posted Slides and demos from my talk on Silverlight 4 From SilverlightCream.com: Silverlight 4 Drag and Drop File Manager Michael Washington has a post up about a Silverlight Drag and Drop File Manager in MVVM, but a secondary important point about the post is that he and Alan Beasley followed strict Designer/Developer rules on this... you recognized Alan's ListBox didn't you? Changing CSS with jQuery syntax in Silverlight using jLight Timmy Kokke is using jLight as introduced in a prior post to interact with the DOM from Silverlight. Essential Silverlight and WPF Skills: The UI Thread, Dispatchers, Background Workers and Async Network Programming Pete Brown has a great backrounder up for WPF and Silverlight devs on threading and networking, good comments too so far. Fluid layout and Fullscreen in Silverlight Paul Yanez has a quick post and demo up on forcing full-screen with a fluid layout, all code included -- and it doesn't take much Data Binding in Silverlight Emil Stoychev has a great long tutorial up on DataBinding in Silverlight ... he hits all the major points with text, samples, and code... definitely one to read! Yet Another MVVM Locator Pattern Another not-necessarily Silverlight post from Jeremy Likness -- but definitely a good one on MVVM and locator patterns. The SpiderWebControl for Silverlight Pavan Podila has a 'SpiderWebControl' for Silverlight 4 up... this is a great network graph control with any sort of feature I can think of... check out the demo, then grab the code... or the other way around, your choice :) Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • TFS Shipping Cadence

    - by Tarun Arora
    Brian Harry has formally announced a change to the TFS shipping cadence from the traditional 2-3 years to production cycle to a more agile and refreshing minimum once in a 3 weeks cycle! The change didn’t happen over night, it was a gradual process which was greatly influenced by moving TFS to the cloud. The thinking started with trying to figure out what the team wanted.  Like people often do, the team started with what they knew and tried to evolve from there.  The team spent a few months thinking through “What if we do major releases every year and minor releases every 6 months?”,  “Major releases every 6 months, patches once a month?”, “What if we do quarterly releases – can we get the release cycle going that fast?”, etc.  The team also spent time debating what constitutes a major release VS a minor release. How much churn are customers willing to tolerate?  The team finally concluded… “When a change this big is necessary – forget where you are and just ask where you want to be and then ask what it would take to get there.” Going forward you will see, Team Foundation Service updates every 3 weeks Visual Studio Client updates quarterly (Limited to VS 2012 for now) Team Foundation Server updates more frequent than every 2 years but details still being worked out.  The team will definitely deliver one this fall. Refer to the complete blog post from Brian Harry here.

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  • Silverlight Cream for February 14, 2011 -- #1047

    - by Dave Campbell
    In this Issue: Mohamed Mosallem, Tony Champion, Gill Cleeren, Laurent Bugnion, Deborah Kurata, Jesse Liberty(-2-), Tim Heuer, Mike Taulty, John Papa, Martin Krüger, and Jeremy Likness. Above the Fold: Silverlight: "Binding to a ComboBox in Silverlight : A Gotcha" Tony Champion WP7: "An Ultra Light Windows Phone 7 MVVM Framework" Jeremy Likness Shoutouts: Steve Wortham has a post up discussing Silverlight 5, HTML5, and what the future may bring From SilverlightCream.com: Silverlight 4.0 Tutorial (12 of N): Collecting Attendees Feedback using Windows Phone 7 Mohamed Mosallem is up to number 12 in his Silverlight tutorial series. He's continuing his RegistrationBooth app, but this time, he's building a WP7 app to give attendee feedback. Binding to a ComboBox in Silverlight : A Gotcha If you've tried to bind to a combobox in Silverlight, you've probably either accomplished this as I have (with help) by having it right once, and continuing, but Tony Champion takes the voodoo out of getting it all working. Getting ready for Microsoft Silverlight Exam 70-506 (Part 5) Gill Cleeren has Part 5 of his exam preparation post up on SilverlightShow. As with the others, he provides many external links to good information. Referencing a picture in another DLL in Silverlight and Windows Phone 7 Laurent Bugnion explains the pitfalls and correct way to reference an image from a dll... good info for loading images such as icons for Silverlight in general and WP7 also. Silverlight MVVM Commanding II Deborah Kurata has a part 2 up on MVVM Commanding. The first part covered the built-in commanding for controls that inherit from ButtonBase... this post goes beyond that into other Silverlight controls. Reactive Drag and Drop Part 1 This Drag and Drop with Rx post by Jesse Liberty is the 4th in his Rx series. He begins with a video from the Rx team and applies reactive programming to mouse movements. Yet Another Podcast #24–Reactive Extensions On the heels of his previous post on Rx, in his latest 'Yet Another Podcast', Jesse Liberty chats with Matthew Podwysocki and Bart De Smet about Reactive Extensions. Silverlight 4 February 2011 Update Released Today Tim Heuer announced the release of the February 2011 Silverlight 4 release. Check out Tim's post for information about what's contained in this release. Blend Bits 25–Templating Part 3 In his 3rd Templating tutorial in BlendBits, Mike Taulty demonstrates the 'Make into Control' option rather than the other way around. Silverlight TV 61: Expert Chat on Deep Zoom, Touch, and Windows Phone John Papa interviews David Kelley in the latest Silverlight TV... David is discussing touch in Silverlight and for WP7 and his WP7 apps in the marketplace. Simple Hyperlinkbutton style Martin Krüger has a cool Hyperlink style available at the Expression Gallery. Interesting visual for entertaining your users. An Ultra Light Windows Phone 7 MVVM Framework Jeremy Likness takes his knowledge of MVVM (Jounce), and WP7 and takes a better look at what he'd really like to have for a WP7 framework. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • Connecting to a new installation of TFS 2010

    - by Enrique Lima
    When the installation and configuration for TFS 2010 is completed, the next step is to connect and use TFS.  There is a Web Access component, but in order for it to serve useful you need to create a project into the Team Project Collection.  This is where Visual Studio 2010 comes in. Open Visual Studio 2010, then click on the Team Explorer Tab (red arrow pointing to it) or go to View > Team Explorer. Once there, click the Connect to Team Project toolbar button This will open up the Connect to Team Project dialog, click on Servers … On the Add/Remove Team Foundation Server dialog, click Add … On the Add Team Foundation Server, enter the name of your server and click ok. If you are prompted for credentials, provide the credentials needed. Once accepted, the server will be listed on the Add/Remove Team Foundations Server dialog, click close. You will be back at the Connect to Team Project dialog, assuming you have one Collection, click Connect. (In the event you have more than one project collection, select the appropriate collection and then click Connect) Your Team Explorer tab will look something like the image below.

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  • Silverlight Cream for February 13, 2011 -- #1046

    - by Dave Campbell
    In this Issue: Loek van den Ouweland, Colin Eberhardt, Rudi Grobler, Joost van Schaik, Mike Taulty(-2-, -3-), Deborah Kurata, David Kelley, Peter Foot, Samuel Jack(-2-), and WindowsPhoneGeek(-2-). Above the Fold: Silverlight: "Silverlight Simple MVVM Commanding" Deborah Kurata WP7: "WP7 CustomInputPrompt control with Cancel button" WindowsPhoneGeek Expression Blend: "Silverlight Templated Image Button with two images" Loek van den Ouweland Shoutouts: Dave Campbell posted a write-up about the project he's on and the use of Sterling: Sterling Object-Oriented Database for ISO 1.0 Released!... Also see Jeremy Likness' post on the 1.0 release: Sterling Object-Oriented Database 1.0 RTM Not necessarily Silverlight, but darn cool, a great control by Sasha Barber: WPF : A Weird 3d based control snoutholder announced new content: Windows Phone 7 QuickStarts Live! From SilverlightCream.com: Silverlight Templated Image Button with two images Loek van den Ouweland has a video tutorial up for creating an ImageButton with a hover state... Expression Blend coolness, and check out the external links he has to their training site. Windows Phone 7 Performance Measurements – Emulator vs. Hardware Colin Eberhardt's latest is a popular post comparing performance metrics between the WP7 emulator and a real device. Mileage may vary, but I'm pretty sure the overall results are conculsive, and should help the way you view your app as you're building in the emulator. WP7: WebClient vs HttpWebRequest Rudi Grobler's latest is a discussion of WebClient and HttpWebRequest, gives coding examples of each plus discussion of why you may choose one over the other... and pay attention to his comment about mobile providers. A Blendable Windows Phone 7 / Silverlight clipping behavior Joost van Schaik posted this WP7/Silverlight clipping behavior he developed because all the other solutions were not blendable. Another really useful piece of code from Joost! Blend Bits 22–Being Stylish Mike Taulty has 3 more episodes in his Blend Bits series... first up is on one Styles... explicit, implicit, inheriting... you name it, he's covering it! Blend Bits 23–Templating Part 1 MIke Taulty then has the beginning of a series within his Blend Bits series on Templating. This is something you just have to either bite the bullet and go with Blend to do, or consume someone else's work. Mike shows us how to do it ourself by tweaking the visual aspects of a checkbox Blend Bits 24–Templating Part 2 In part 2 of the Templating series, Mike Taulty digs deeper into Blend and cracks open the Listbox control to take a bunch of the inner elements out for a spin... fun stuff and great tutorial, Mike! Silverlight Simple MVVM Commanding Deborah Kurata has another great MVVM post up... if you don't have your head wrapped around commanding yet, this is a good place to start that process... VB and C# as always. App Development for Windows Phone 7 101 David Kelley goes through the basics of producing a WP7 app both from the Silverlight and XNA side... good info and good external links to get you going. Copyable TextBlock for Windows Phone Peter Foot takes a look at the Copy/Paste functionality in WP7 and how to apply it to a TextBlock... which is NOT an out-of-the-box solution. How to deploy to, and debug, multiple instances of the Windows Phone 7 emulator Samuel Jack has a couple posts up this week... first is this clever one on running multiple copies of the emulator at once... too cool for debugging a multi-player game! Multi-player enabling my Windows Phone 7 game: Day 3 – The Server Side Samuel Jack's latest is a detailed look at his day 3 adventure of taking his multi-player game to WP7... lots of information and external links... what do you say, give him another day? :) WP7 CustomInputPrompt control with Cancel button WindowsPhoneGeek has a couple more posts up... first is this "CustomInputPrompt" control based off the InputPrompt from Coding4Fun. Implementing Windows Phone 7 DataTemplateSelector and CustomDataTemplateSelector In his latest post, WindowsPhoneGeek writes a DataTemplateSelector to allow different data templates for different list elements based on the type of the element. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • Review: A Quick Look at Reflector

    - by James Michael Hare
    I, like many, was disappointed when I heard that Reflector 7 was not free, and perhaps that’s why I waited so long to try it and just kept using my version 6 (which continues to be free).  But though I resisted for so long, I longed for the better features that were being developed, and began to wonder if I should upgrade.  Thus, I began to look into the features being offered in Reflector 7.5 to see what was new. Multiple Editions Reflector 7.5 comes in three flavors, each building on the features of the previous version: Standard – Contains just the Standalone application ($70) VS – Same as Standard but adds Reflector Object Browser for Visual Studio ($130) VSPro – Same as VS but adds ability to set breakpoints and step into decompiled code ($190) So let’s examine each of these features. The Standalone Application (Standard, VS, VSPro editions) Popping open Reflector 7.5 and looking at the GUI, we see much of the same familiar features, with a few new ones as well: Most notably, the disassembler window now has a tabbed window with navigation buttons.  This makes it much easier to back out of a deep-dive into many layers of decompiled code back to a previous point. Also, there is now an analyzer which can be used to determine dependencies for a given method, property, type, etc. For example, if we select System.Net.Sockets.TcpClient and hit the Analyze button, we’d see a window with the following nodes we could expand: This gives us the ability to see what a given type uses, what uses it, who exposes it, and who instantiates it. Now obviously, for low-level types (like DateTime) this list would be enormous, but this can give a lot of information on how a given type is connected to the larger code ecosystem. One of the other things I like about using Reflector 7.5 is that it does a much better job of displaying iterator blocks than Reflector 6 did. For example, if you were to take a look at the Enumerable.Cast() extension method in System.Linq, and dive into the CastIterator in Reflector 6, you’d see this: But now, in Reflector 7.5, we see the iterator logic much more clearly: This is a big improvement in the quality of their code disassembler and for me was one of the main reasons I decided to take the plunge and get version 7.5. The Reflector Object Browser (VS, VSPro editions) If you have the .NET Reflector VS or VSPro editions, you’ll find you have in Visual Studio a Reflector Object Browser window available where you can select and decompile any assembly right in Visual Studio. For example, if you want to take a peek at how System.Collections.Generic.List<T> works, you can either select List<T> in the Reflector Object Browser, or even simpler just select a usage of it in your code and CTRL + Click to dive in. – And it takes you right to a source window with the decompiled source: Setting Breakpoints and Stepping Into Decompiled Code (VSPro) If you have the VSPro edition, in addition to all the things said above, you also get the additional ability to set breakpoints in this decompiled code and step through it as if it were your own code: This can be a handy feature when you need to see why your code’s use of a BCL or other third-party library isn’t working as you expect. Summary Yes, Reflector is no longer free, and yes, that’s a bit of a bummer. But it always was and still is a very fine tool. If you still have Reflector 6, you aren’t forced to upgrade any longer, but getting the nicer disassembler (especially for iterator blocks) and the handy VS integration is worth at least considering upgrading for.  So I leave it up to you, these are some of the features of Reflector 7.5, what’s your thoughts? Technorati Tags: .NET,Reflector

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  • CoffeeScript Test Framework

    - by Liam McLennan
    Tonight the Brisbane Alt.NET group is doing a coding dojo. I am hoping to talk someone into pairing with me to solve the kata in CoffeeScript. CoffeeScript is an awesome language, half javascript, half ruby, that compiles to javascript. To assist with tonight’s dojo I wrote the following micro test framework for CoffeeScript: <html> <body> <div> <h2>Test Results:</h2> <p class='results' /> </div> <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js" type="text/javascript"></script> <script type="text/coffeescript"> # super simple test framework test: { write: (s) -> $('.results').append(s + '<br/>') assert: (b, message...) -> test.write(if b then "pass" else "fail: " + message) tests: [] exec: () -> for t in test.tests test.write("<br/><b>$t.name</b>") t.func() } # add some tests test.tests.push { name: "First Test" func: () -> test.assert(true) } test.tests.push { name: "Another Test" func: () -> test.assert(false, "You loose") } # run them test.exec(test.tests) </script> <script type="text/javascript" src="coffee-script.js"></script> </body> </html> It’s not the prettiest, but as far as I know it is the only CoffeeScript test framework in existence. Of course, I could just use one of the javascript test frameworks but that would be no fun. To get this example to run you need the coffeescript compiler in the same directory as the page.

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  • Ranking - an Introduction

    - by PointsToShare
    © 2011 By: Dov Trietsch. All rights reserved Ranking Ranking is quite common in the internet. Readers are asked to rank their latest reading by clicking on one of 5 (sometimes 10) stars. The number of stars is then converted to a number and the average number of stars as selected by all the readers is proudly (or shamefully) displayed for future readers. SharePoint 2007 lacked this feature altogether. SharePoint 2010 allows the users to rank items in a list or documents in a library (the two are actually the same because a library is actually a list). But in SP2010 the computation of the average is done later on a timer rather than on-the-spot as it should be. I suspect that the reason for this shortcoming is that they did not involve a mathematician! Let me explain. Ranking is kept in a related list. When a user rates a document the rank-list is added an item with the item id, the user name, and his number of stars. The fact that a user already ranked an item prevents him from ranking it again. This prevents the creator of the item from asking his mother to rank it a 5 and do it 753 times, thus stacking the ballot. Some systems will allow a user to change his rating and this will be done by updating the rank-list item. Now, when the timer kicks off, the list is spanned and for each item the rank-list items containing this id are summed up and divided by the number of votes thus yielding the new average. This is obviously very time consuming and very server intensive. In the 18th century an early actuary named James Dodson used what the great Augustus De Morgan (of De Morgan’s law) later named Commutation tables. The labor involved in computing a life insurance premium was staggering and also very error prone. Clerks with pencil and paper would multiply and add mountains of numbers to do the task. The more steps the greater the probability of error and the more expensive the process. Commutation tables created a “summary” of many steps and reduced the work 100 fold. So had Microsoft taken a lesson in the history of computation, they would have developed a much faster way for rating that may be done in real-time and is also 100 times faster and less CPU intensive. How do we do this? We use a form of commutation. We always keep the number of votes and the total of stars. One simple division gives us the average. So we write an event receiver. When a vote is added, we just add the stars to the total-stars and 1 to the number of votes. We then recomputed the average. When a vote is updated, we reduce the total by the old vote, increase it by the new vote and leave the number of votes the same. Again we do the division to get the new average. When a vote is deleted (highly unlikely and maybe even prohibited), we reduce the total by that vote and reduce the number of votes by 1… Gone are the days of spanning lists, counting items, and tallying votes and we have no need for a timer process to run it all. This is the first of a few treatises on ranking. Even though I discussed the math and the history thereof, in here I am only going to solve the presentation issue. I wanted to create the CSS and Jscript needed to display the stars, create the various effects like hovering and clicking (onmouseover, onmouseout, onclick, etc.) and I wanted to create a general solution with any number of stars. When I had it all done, I created the ranking game so that I could test it. The game is interesting in and on itself, so here it is (or go to the games page and select “rank the stars”). BTW, when you play it, look at the source code and see how it was all done.  Next, how the 5 stars are displayed in the New and Update forms. When the whole set of articles will be done, you’ll be able to create the complete solution. That’s all folks!

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  • Type of Blobs

    - by kaleidoscope
    With the release of Windows Azure November 2009 CTP, now we have two types of blobs. Block Blob - This blob type is in place since PDC 2008 and is optimized for streaming workloads. [Max Size allowed : 200GB] Page Blob - With November 2009 CTP release, a new blob type is added which is optimized for random read / writes called Page Blob. [Max Size allowed : 1TB] More details can be found at: http://geekswithblogs.net/IUnknown/archive/2009/11/16/azure-november-ctp-announced.aspx Amit, S

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  • C#/.NET Little Wonders: Using &lsquo;default&rsquo; to Get Default Values

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Today’s little wonder is another of those small items that can help a lot in certain situations, especially when writing generics.  In particular, it is useful in determining what the default value of a given type would be. The Problem: what’s the default value for a generic type? There comes a time when you’re writing generic code where you may want to set an item of a given generic type.  Seems simple enough, right?  We’ll let’s see! Let’s say we want to query a Dictionary<TKey, TValue> for a given key and get back the value, but if the key doesn’t exist, we’d like a default value instead of throwing an exception. So, for example, we might have a the following dictionary defined: 1: var lookup = new Dictionary<int, string> 2: { 3: { 1, "Apple" }, 4: { 2, "Orange" }, 5: { 3, "Banana" }, 6: { 4, "Pear" }, 7: { 9, "Peach" } 8: }; And using those definitions, perhaps we want to do something like this: 1: // assume a default 2: string value = "Unknown"; 3:  4: // if the item exists in dictionary, get its value 5: if (lookup.ContainsKey(5)) 6: { 7: value = lookup[5]; 8: } But that’s inefficient, because then we’re double-hashing (once for ContainsKey() and once for the indexer).  Well, to avoid the double-hashing, we could use TryGetValue() instead: 1: string value; 2:  3: // if key exists, value will be put in value, if not default it 4: if (!lookup.TryGetValue(5, out value)) 5: { 6: value = "Unknown"; 7: } But the “flow” of using of TryGetValue() can get clunky at times when you just want to assign either the value or a default to a variable.  Essentially it’s 3-ish lines (depending on formatting) for 1 assignment.  So perhaps instead we’d like to write an extension method to support a cleaner interface that will return a default if the item isn’t found: 1: public static class DictionaryExtensions 2: { 3: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 4: TKey key, TValue defaultIfNotFound) 5: { 6: TValue value; 7:  8: // value will be the result or the default for TValue 9: if (!dict.TryGetValue(key, out value)) 10: { 11: value = defaultIfNotFound; 12: } 13:  14: return value; 15: } 16: } 17:  So this creates an extension method on Dictionary<TKey, TValue> that will attempt to get a value using the given key, and will return the defaultIfNotFound as a stand-in if the key does not exist. This code compiles, fine, but what if we would like to go one step further and allow them to specify a default if not found, or accept the default for the type?  Obviously, we could overload the method to take the default or not, but that would be duplicated code and a bit heavy for just specifying a default.  It seems reasonable that we could set the not found value to be either the default for the type, or the specified value. So what if we defaulted the type to null? 1: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 2: TKey key, TValue defaultIfNotFound = null) // ... No, this won’t work, because only reference types (and Nullable<T> wrapped types due to syntactical sugar) can be assigned to null.  So what about a calling parameterless constructor? 1: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 2: TKey key, TValue defaultIfNotFound = new TValue()) // ... No, this won’t work either for several reasons.  First, we’d expect a reference type to return null, not an “empty” instance.  Secondly, not all reference types have a parameter-less constructor (string for example does not).  And finally, a constructor cannot be determined at compile-time, while default values can. The Solution: default(T) – returns the default value for type T Many of us know the default keyword for its uses in switch statements as the default case.  But it has another use as well: it can return us the default value for a given type.  And since it generates the same defaults that default field initialization uses, it can be determined at compile-time as well. For example: 1: var x = default(int); // x is 0 2:  3: var y = default(bool); // y is false 4:  5: var z = default(string); // z is null 6:  7: var t = default(TimeSpan); // t is a TimeSpan with Ticks == 0 8:  9: var n = default(int?); // n is a Nullable<int> with HasValue == false Notice that for numeric types the default is 0, and for reference types the default is null.  In addition, for struct types, the value is a default-constructed struct – which simply means a struct where every field has their default value (hence 0 Ticks for TimeSpan, etc.). So using this, we could modify our code to this: 1: public static class DictionaryExtensions 2: { 3: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 4: TKey key, TValue defaultIfNotFound = default(TValue)) 5: { 6: TValue value; 7:  8: // value will be the result or the default for TValue 9: if (!dict.TryGetValue(key, out value)) 10: { 11: value = defaultIfNotFound; 12: } 13:  14: return value; 15: } 16: } Now, if defaultIfNotFound is unspecified, it will use default(TValue) which will be the default value for whatever value type the dictionary holds.  So let’s consider how we could use this: 1: lookup.GetValueOrDefault(1); // returns “Apple” 2:  3: lookup.GetValueOrDefault(5); // returns null 4:  5: lookup.GetValueOrDefault(5, “Unknown”); // returns “Unknown” 6:  Again, do not confuse a parameter-less constructor with the default value for a type.  Remember that the default value for any type is the compile-time default for any instance of that type (0 for numeric, false for bool, null for reference types, and struct will all default fields for struct).  Consider the difference: 1: // both zero 2: int i1 = default(int); 3: int i2 = new int(); 4:  5: // both “zeroed” structs 6: var dt1 = default(DateTime); 7: var dt2 = new DateTime(); 8:  9: // sb1 is null, sb2 is an “empty” string builder 10: var sb1 = default(StringBuilder()); 11: var sb2 = new StringBuilder(); So in the above code, notice that the value types all resolve the same whether using default or parameter-less construction.  This is because a value type is never null (even Nullable<T> wrapped types are never “null” in a reference sense), they will just by default contain fields with all default values. However, for reference types, the default is null and not a constructed instance.  Also it should be noted that not all classes have parameter-less constructors (string, for instance, doesn’t have one – and doesn’t need one). Summary Whenever you need to get the default value for a type, especially a generic type, consider using the default keyword.  This handy word will give you the default value for the given type at compile-time, which can then be used for initialization, optional parameters, etc. Technorati Tags: C#,CSharp,.NET,Little Wonders,default

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  • Virtual Brown Bag: Ruby Newbies, Mockups, There *is* an I in SOLID, fuv

    - by Brian Schroer
    At this week's Virtual Brown Bag meeting: Claudio pointed us to Try Ruby! and Rails For Zombies, two sites to educate Ruby newbies We looked at the free version of Balsamiq, and other online mockup sites George walked us through a refactoring to isolate roles and adhere to the Interface Segregation Principle (the "I" in SOLID) We laughed at fuv, the code editor for "real programmers" For detailed notes, links, and the video recording, go to the VBB wiki page: https://sites.google.com/site/vbbwiki/main_page/2011-02-10

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  • Connecting Visual Studio 2008 SP1 to TFS 2010

    - by Enrique Lima
    Introduction You have installed Team Foundation Server 2010, you are ready to go.  Your client is Visual Studio 2008 SP1, and need to connect to TFS 2010. Here is the story, the steps to configure Team Explorer are almost the same … meaning, you will open Visual Studio, then go to Team Explorer.  At that point you will Add an Existing Project, this where we connect to TFS.  Except, we get this: Now what?!?  We need to install the Visual Studio Team System 2008 Service Pack 1 Forward Compatibility Update for Team Foundation Server 2010.  Where to get it from? TFS 2010 installation media Microsoft’s Download Center Update Installation We arrive at the Welcome Screen for the Update, click Next Next comes the license screen, accept the license, by selecting the checkbox, then click next. The installation process will start at that point. Once it completes, click on Finish. Second Try Time to attempt to connect again. We are back to working with Team Explorer, and Adding an existing project.  There is a formula to be successful with this. protocol://servername:port/tfs/<name of collection> protocol = http or https servername = your tfs 2010 server port = 8080 by default, or the custom port you are using /tfs = I am assuming the default too /<name of collection = the name of the collection that was provisioned. Once the values are provided, click OK, then close. At this point you should see a listing of Projects available within the TFS 2010 collection. Select the project and click OK.  You will now see this listed in Team Explorer.

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  • Chuck Norris Be Thy Name

    - by Robz / Fervent Coder
    Chuck Norris doesn’t program with a keyboard. He stares the computer down until it does what he wants. All things need a name. We’ve tossed around a bunch of names for the framework of tools we’ve been working on, but one we kept coming back to was Chuck Norris. Why did we choose Chuck Norris? Well Chuck Norris sort of chose us. Everything we talked about, the name kept drawing us closer to it. We couldn’t escape Chuck Norris, no matter how hard we tried. So we gave in. Chuck Norris can divide by zero. What is the Chuck Norris Framework? @drusellers and I have been working on a variety of tools: WarmuP - http://github.com/chucknorris/warmup (Template your entire project/solution and create projects ready to code - From Zero to a Solution with everything in seconds. Your templates, your choices.) UppercuT - http://projectuppercut.org (Build with Conventions - Professional Builds in Moments, Not Days!) | Code also at http://github.com/chucknorris/uppercut DropkicK - http://github.com/chucknorris/dropkick (Deploy Fluently) RoundhousE - http://projectroundhouse.org (Professional Database Management with Versioning) | Code also at http://github.com/chucknorris/roundhouse SidePOP - http://sidepop.googlecode.com (Does your application need to check email?) HeadlocK - http://github.com/chucknorris/headlock (Hash a directory so you can later know if anything has changed) Others – still in concept or vaporware People ask why we choose such violent names for each tool of our framework? At first it was about whipping your code into shape, but after awhile the naming became, “How can we relate this to Chuck Norris?” People also ask why we uppercase the last letter of each name. Well, that’s more about making you ask questions…but there are a few reasons for it. Project managers never ask Chuck Norris for estimations…ever. The class object inherits from Chuck Norris Chuck Norris doesn’t need garbage collection because he doesn’t call .Dispose(), he calls .DropKick() So what are you waiting for? Join the Google group today, download and play with the tools. And lastly, welcome to Chuck Norris. Or should I say Chuck Norris welcomes you…

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  • Silverlight Cream for March 09, 2011 -- #1057

    - by Dave Campbell
    In this Issue: Dennis Doomen, Peter Kuhn, Michael Crump, Joe McBride, Martin Krüger, Jeremy Likness, Manas Patnaik, Jesse Liberty(-2-), WindowsPhoneGeek(-2-). Above the Fold: Silverlight: "A highlighting AutoCompleteBox in Silverlight" Peter Kuhn WP7: "WP7 WatermarkedTextBox custom control" WindowsPhoneGeek Training: "" Shoutouts: Karl Shifflett announced that he and Josh Smith have heard the developers and released a demo: Mole 2010 Demo Released This is a somewhat older post, but the material is good and I was reminded of it while talking to Josh Smith at the MVP summit last week: Advanced MVVM ... money well-spent From SilverlightCream.com: Introducing the Silverlight Cookbook Dennis Doomen unveils a Codeplex site "containing a Silverlight 4 app that includes most of the complexities you might run into" ... I'm tagging this in my WynApse outlookbar... great stuff, Dennis! A highlighting AutoCompleteBox in Silverlight Peter Kuhn took on a task in response to a forum query and created a highlighting AutoCompleteBox, and is giving it to us... this really looks cool, Peter, and great explanation. Taking a look at the Mindscape Phone Elements for WP7. Michael Crump takes a good look at the Mindscape Phone Elements for WP7... and if you read closely you might still be able to get a free license! Windows Phone – “Can’t connect to your phone. Disconnect it, Restart it, then try connecting again.” Joe McBride explains a way out of an issue that many should be seeing as we repave or replace machines... how to get our device recognized on the updated machine... without giving cryptic messages. How to: only with the full visibility of an application in the browser window start an action Martin Krüger continues his journey in starting storyboards and tackles the condition that the application is completely in the browser window prior to the storyboard starting. A Numeric Input Control for Windows Phone 7 Jeremy Likness came up with a great idea for numeric input for WP7 ... you'll smile when you see it, but what a great idea... and a NumericTextBox to go along with it. Performing CRUD on Relational Data (Multiple table) using RIA in SL4 Manas Patnaik has a post up that breaks the normal blog post or demo mold by having two tables with a relational constraint and doing CRUD operations on them. Plenty of diagrams and good information. Select Many: Reactive Extensions’ Mother Of All Operators [Chaining] Jesse Liberty has part 9 in his Rx series up, and is looking at SelectMany this time, and chaining calls. He's using WPF for the sample, but the goodness is all there for us Silverlight guys too. The Full Stack 8–Adding Search to the Phone Client Jesse Liberty and Jon Galloway have part 8 of their Full Stack series up ... this is the MVC3, ASP.NET, Silverlight, and WP7 app development series... this time out they're putting Search in the Phone client. All about ResourceDictionary in WP7 WindowsPhoneGeek is discussing ResourceDictionaries in this post... beginning with What is a ResourceDictionary and continuing out through creating and using one, plus a good comment on merging. WP7 WatermarkedTextBox custom control In his next post, WindowsPhoneGeek walks us through the creation of a WatermarkedTextBox for WP7 right from the derivation from TextBox... very nice tutorial and lots of code/examples. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • TechEd 2012: Office, SharePoint And More Office

    - by Tim Murphy
    I haven’t spent any time looking at Office 365 up to this point.  I met Donovan Follette on the flight down from Chicago.  I also got to spend some time discussing the product offerings with him at the TechExpo and that sealed my decision to attend this session. The main actor of his presentation is the BCS – Business Connectivity Services. He explained that while this feature has existed in on-site SharePoint it is a valuable new addition to Office 365 SharePoint Online.  If you aren’t familiar with the BCS, it allows you to leverage non-SharePoint enterprise data source from SharePoint.  The greatest benefactor is the end users who can leverage the data using a variety of Office products and more.  The one thing I haven’t shaken my skepticism of is the use of SharePoint Designer which Donovan used to create a WCF service.  It is mostly my tendency to try to create solutions that can be managed through the whole application life cycle.  It the past migrating through test environments has been near impossible with anything other than content created by SharePiont Designer. There is a lot of end user power here.  The biggest consideration I think you need to examine when reaching from you enterprise LOB data stores out to an online service and back is that you are going to take a performance hit.  This means that you have to be very aware of how you configure these integrated self serve solutions.  As a rule make sure you are using the right tool for the right situation. I appreciated that he showed both no code and code solutions for the consumer of the LOB data.  I came out of this session much better informed about the possibilities around this product. del.icio.us Tags: Office 365,SharePoint Online,TechEd,TechEd 2012

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  • ASP.NET MVC 2 RTM Available

    - by Shaun
    Shiju Varghese posted an article on his(her) blog and said that the RTM of the ASP.NET MVC 2 had been released and available to download. You can get the installation packeage and the release note here. And based on the release note there’s no breaking changes from RC2 to RTM. Let’s play with the new ASP.NET MVC and look forward the Visual Studio 2010 RTM.

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  • Microsoft Press Deal of the Day - 9/Jul/2012 - Windows® Communication Foundation 4 Step by Step

    - by TATWORTH
    Today's Deal of the Day from Microsoft Press at http://shop.oreilly.com/product/0790145302403.do?code=MSDEAL is Windows® Communication Foundation 4 Step by Step"Teach yourself the essentials of Windows Communication Foundation (WCF) 4 -- one step at a time. With this practical, learn-by-doing tutorial, you get the clear guidance and hands-on examples you need to begin creating Web services for robust Windows-based business applications. Discover how to: Build and host SOAP and REST servicesMaintain service contracts and data contractsControl configuration and communications programmaticallyImplement message encryption, authentication, and authorizationManage identity with Windows CardSpaceBegin working with Windows Workflow Foundation to create scalable and durable business servicesImplement service discovery and message routingOptimize performance with service throttling, encoding, and streamingIntegrate WCF services with ASP.NET clients and enterprise services components"  Note the comment:Use code: MSDEAL

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  • Windows Embedded Forums

    - by Luca Calligaris
    Here are the forums about Windows Embedded: Windows Embedded Standard Windows Embedded Compact Platform Development Windows Embedded Compact Managed Application Development Windows Embedded Compact Native Application Development The first forum has been online for some time while those about Windows Embedded Compact have been welcomed by Olivier Bloch a couple of hours ago. As I discuss in the previous post the public MS newsgroups will close between June 1, 2010 and October 1, 2010, starting from those with less traffic. The embedded NG's will be probably close at the beginning of the period since, for some reasons I do not understand, they're not so popular as those devoted to, let's say, Office. The forums will substitute the newsgroups so prepare to switch over soon!

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  • Temporarily disabling foreign key constraints in SQL Server

    - by Renso
    Originally posted on: http://geekswithblogs.net/renso/archive/2013/06/24/temporarily-disabling-foreign-key-constraints-in-sql-server.aspxGoal: Is to temporarily disable all foreign key constraint and later enable the Constraint again?Solutions-- Disable all the constraint in databaseEXEC sp_msforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT all"-- Enable all the constraint in databaseEXEC sp_msforeachtable "ALTER TABLE ? WITH CHECK CHECK CONSTRAINT all"

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  • ReplaceBetweenTags function with delegate to describe transformation

    - by Michael Freidgeim
    I've created a function that allow to replace content between XML tags with data, that depend on original content within tag, in particular to MAsk credit card number.The function uses MidBetween extension from My StringHelper class /// <summary> /// /// </summary> /// <param name="thisString"></param> /// <param name="openTag"></param> /// <param name="closeTag"></param> /// <param name="transform"></param> /// <returns></returns> /// <example> /// // mask <AccountNumber>XXXXX4488</AccountNumber> ///requestAsString  = requestAsString.ReplaceBetweenTags("<AccountNumber>", "</AccountNumber>", CreditCard.MaskedCardNumber); ///mask cvv ///requestAsString = requestAsString.ReplaceBetweenTags("<FieldName>CC::VerificationCode</FieldName><FieldValue>", "</FieldValue>", cvv=>"XXX"); /// </example> public static string ReplaceBetweenTags(this string thisString, string openTag, string closeTag, Func<string, string> transform) { //See also http://stackoverflow.com/questions/1359412/c-sharp-remove-text-in-between-delimiters-in-a-string-regex string sRet = thisString; string between = thisString.MidBetween(openTag, closeTag, true); if (!String.IsNullOrEmpty(between)) sRet=thisString.Replace(openTag + between + closeTag, openTag + transform(between) + closeTag); return sRet; } public static string ReplaceBetweenTags(this string thisString, string openTag, string closeTag, string newValue) { //See also http://stackoverflow.com/questions/1359412/c-sharp-remove-text-in-between-delimiters-in-a-string-regex string sRet = thisString; string between = thisString.MidBetween(openTag, closeTag, true); if (!String.IsNullOrEmpty(between)) sRet = thisString.Replace(openTag + between + closeTag, openTag + newValue + closeTag); return sRet; }

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  • Extending QuickBooks Reporting with the QuickBooks ADO.NET Data Provider

    - by dataintegration
    The ADO.NET Provider for QuickBooks comes with several reports you may request from QuickBooks by default. However, there are many more that are not readily available. The ADO.NET Provider for QuickBooks makes it easy for you to create new reports and customize existing ones. In this article, we will illustrate how to create your own report and retrieve it from the Server Explorer in Visual Studio. For this example we will show how to create an Item Profitability Report. Creating the report script file Step 1: Download the sample reports available here. Extract them to a folder of your choice. Step 2: Make a copy of the ReportGeneralSummary.rsd file and rename it to ItemProfitability.rsd. Then open the file in any text editor. Step 3: Open the installation directory of the ADO.NET Provider for QuickBooks. Under the \db\ folder, locate the ReportJob.rsb file. Open this file in another text editor. Note: Although we are using ReportJob.rsb for this example, other reports may be contained in other Report*.rsb files. We recommend consulting the included help file and first locating the Report stored procedure and ReportType you are looking for. Otherwise, you may open each Report*.rsb file and look under the "reporttype" input for the report you are attempting to create. Step 4: First, let's rename the title of ItemProfitability.rsd. Near the top of the file you will see a title and description. Change the title to match the name of the file. Change the description to anything you like. For example: <rsb:info title="ItemProfitability" description="Executes my custom report."> Just below the Title, there are a number of columns. The Id represents the row number. The RowType represents the type of data returned by QuickBooks. The ColumnValue* columns represent all of the column data returned by QuickBooks. In some instances, we may need to add additional ColumnValue columns. Step 5: To add additional ColumnValue columns, simply copy the last column, paste it directly below, and continue increasing the numerical value at end of the attribute name. For example: <attr name="ColumnValue9" xs:type="string" readonly="true" required="false" desc="Represents a column of data."/> <attr name="ColumnValue10" xs:type="string" readonly="true" required="false" desc="Represents a column of data."/> <attr name="ColumnValue11" xs:type="string" readonly="true" required="false" desc="Represents a column of data."/> <attr name="ColumnValue12" xs:type="string" readonly="true" required="false" desc="Represents a column of data."/> ... Caution: Do not rename the ColumnValue* definitions themselves. They are generalized so that we can understand each type of report returned by QuickBooks. Renaming them to something other than ColumnValue* will cause your columns to return with null values. Step 6: Now let's update the available inputs for the table. From the ReportJob.rsb file, copy all of the input elements into ItemProfitability under the "Psuedo-Column definitions" comment. You will be replacing the existing input elements in ItemProfitability with inputs from ReportJob. When you are done, it should look like this: <!-- Psuedo-Column definitions --> <input name="reporttype" description="The type of the report." value="ITEMESTIMATESVSACTUALS,ITEMPROFITABILITY,JOBESTIMATESVSACTUALSDETAIL,JOBESTIMATESVSACTUALSSUMMARY,JOBPROFITABILITYDETAIL,JOBPROFITABILITYSUMMARY," default="ITEMESTIMATESVSACTUALS" /> <input name="reportperiod" description="Report date range in the format (fromdate:todate), and either value may be omitted for an open ended range (e.g. 2009-12-25:). Supported date format: yyyy-MM-dd." /> <input name="reportdaterangemacro" description="Use a predefined date range." value="ALL,TODAY,THISWEEK,THISWEEKTODATE,THISMONTH,THISMONTHTODATE,THISQUARTER,THISQUARTERTODATE,THISYEAR,THISYEARTODATE,YESTERDAY,LASTWEEK,LASTWEEKTODATE,LASTMONTH,LASTMONTHTODATE,LASTQUARTER,LASTQUARTERTODATE,LASTYEAR,LASTYEARTODATE,NEXTWEEK,NEXTFOURWEEKS,NEXTMONTH,NEXTQUARTER,NEXTYEAR," default="ALL" /> ... Step 7: Now let's update the operationname attribute. This needs to match the same operationname used by ReportJob. After you have copied the correct value from ReportJob.rsb, the operationname in ItemProfitability should look like so: <rsb:set attr="operationname" value="qbReportJob"/> Step 8: There is one more thing we can do to make this a true Item Profitability report. We can remove the reporttype input and hardcode the value. To do this, copy and paste the rsb:set used for operationname. Then rename the attr and value to match the name and value you want to use. For example: <rsb:set attr="operationname" value="qbReportJob"/> <rsb:set attr="reporttype" value="ITEMPROFITABILITY"/> After this you can remove the input for reporttype. Now that you have your own report file, we can move on to displaying the report in the Visual Studio server explorer. Accessing the report through the Data Provider Step 1: Open Visual Studio. In the Server Explorer, configure a new connection with the QuickBooks Data Provider. Step 2: For the Location connection string property, enter the directory where the new report has been saved to. Step 3: The new report should appear as a new view in the Server Explorer. Let's retrieve data from it. Step 4: You can specify any inputs in the WHERE clause. New Report Example Script To help you get started using this new QuickBooks Data Provider report, you will need to download the QuickBooks ADO.NET Data Provider and the fully functional sample script.

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  • C#/.NET Little Wonders: Fun With Enum Methods

    - by James Michael Hare
    Once again lets dive into the Little Wonders of .NET, those small things in the .NET languages and BCL classes that make development easier by increasing readability, maintainability, and/or performance. So probably every one of us has used an enumerated type at one time or another in a C# program.  The enumerated types we create are a great way to represent that a value can be one of a set of discrete values (or a combination of those values in the case of bit flags). But the power of enum types go far beyond simple assignment and comparison, there are many methods in the Enum class (that all enum types “inherit” from) that can give you even more power when dealing with them. IsDefined() – check if a given value exists in the enum Are you reading a value for an enum from a data source, but are unsure if it is actually a valid value or not?  Casting won’t tell you this, and Parse() isn’t guaranteed to balk either if you give it an int or a combination of flags.  So what can we do? Let’s assume we have a small enum like this for result codes we want to return back from our business logic layer: 1: public enum ResultCode 2: { 3: Success, 4: Warning, 5: Error 6: } In this enum, Success will be zero (unless given another value explicitly), Warning will be one, and Error will be two. So what happens if we have code like this where perhaps we’re getting the result code from another data source (could be database, could be web service, etc)? 1: public ResultCode PerformAction() 2: { 3: // set up and call some method that returns an int. 4: int result = ResultCodeFromDataSource(); 5:  6: // this will suceed even if result is < 0 or > 2. 7: return (ResultCode) result; 8: } So what happens if result is –1 or 4?  Well, the cast does not fail, so what we end up with would be an instance of a ResultCode that would have a value that’s outside of the bounds of the enum constants we defined. This means if you had a block of code like: 1: switch (result) 2: { 3: case ResultType.Success: 4: // do success stuff 5: break; 6:  7: case ResultType.Warning: 8: // do warning stuff 9: break; 10:  11: case ResultType.Error: 12: // do error stuff 13: break; 14: } That you would hit none of these blocks (which is a good argument for always having a default in a switch by the way). So what can you do?  Well, there is a handy static method called IsDefined() on the Enum class which will tell you if an enum value is defined.  1: public ResultCode PerformAction() 2: { 3: int result = ResultCodeFromDataSource(); 4:  5: if (!Enum.IsDefined(typeof(ResultCode), result)) 6: { 7: throw new InvalidOperationException("Enum out of range."); 8: } 9:  10: return (ResultCode) result; 11: } In fact, this is often recommended after you Parse() or cast a value to an enum as there are ways for values to get past these methods that may not be defined. If you don’t like the syntax of passing in the type of the enum, you could clean it up a bit by creating an extension method instead that would allow you to call IsDefined() off any isntance of the enum: 1: public static class EnumExtensions 2: { 3: // helper method that tells you if an enum value is defined for it's enumeration 4: public static bool IsDefined(this Enum value) 5: { 6: return Enum.IsDefined(value.GetType(), value); 7: } 8: }   HasFlag() – an easier way to see if a bit (or bits) are set Most of us who came from the land of C programming have had to deal extensively with bit flags many times in our lives.  As such, using bit flags may be almost second nature (for a quick refresher on bit flags in enum types see one of my old posts here). However, in higher-level languages like C#, the need to manipulate individual bit flags is somewhat diminished, and the code to check for bit flag enum values may be obvious to an advanced developer but cryptic to a novice developer. For example, let’s say you have an enum for a messaging platform that contains bit flags: 1: // usually, we pluralize flags enum type names 2: [Flags] 3: public enum MessagingOptions 4: { 5: None = 0, 6: Buffered = 0x01, 7: Persistent = 0x02, 8: Durable = 0x04, 9: Broadcast = 0x08 10: } We can combine these bit flags using the bitwise OR operator (the ‘|’ pipe character): 1: // combine bit flags using 2: var myMessenger = new Messenger(MessagingOptions.Buffered | MessagingOptions.Broadcast); Now, if we wanted to check the flags, we’d have to test then using the bit-wise AND operator (the ‘&’ character): 1: if ((options & MessagingOptions.Buffered) == MessagingOptions.Buffered) 2: { 3: // do code to set up buffering... 4: // ... 5: } While the ‘|’ for combining flags is easy enough to read for advanced developers, the ‘&’ test tends to be easy for novice developers to get wrong.  First of all you have to AND the flag combination with the value, and then typically you should test against the flag combination itself (and not just for a non-zero)!  This is because the flag combination you are testing with may combine multiple bits, in which case if only one bit is set, the result will be non-zero but not necessarily all desired bits! Thanks goodness in .NET 4.0 they gave us the HasFlag() method.  This method can be called from an enum instance to test to see if a flag is set, and best of all you can avoid writing the bit wise logic yourself.  Not to mention it will be more readable to a novice developer as well: 1: if (options.HasFlag(MessagingOptions.Buffered)) 2: { 3: // do code to set up buffering... 4: // ... 5: } It is much more concise and unambiguous, thus increasing your maintainability and readability. It would be nice to have a corresponding SetFlag() method, but unfortunately generic types don’t allow you to specialize on Enum, which makes it a bit more difficult.  It can be done but you have to do some conversions to numeric and then back to the enum which makes it less of a payoff than having the HasFlag() method.  But if you want to create it for symmetry, it would look something like this: 1: public static T SetFlag<T>(this Enum value, T flags) 2: { 3: if (!value.GetType().IsEquivalentTo(typeof(T))) 4: { 5: throw new ArgumentException("Enum value and flags types don't match."); 6: } 7:  8: // yes this is ugly, but unfortunately we need to use an intermediate boxing cast 9: return (T)Enum.ToObject(typeof (T), Convert.ToUInt64(value) | Convert.ToUInt64(flags)); 10: } Note that since the enum types are value types, we need to assign the result to something (much like string.Trim()).  Also, you could chain several SetFlag() operations together or create one that takes a variable arg list if desired. Parse() and ToString() – transitioning from string to enum and back Sometimes, you may want to be able to parse an enum from a string or convert it to a string - Enum has methods built in to let you do this.  Now, many may already know this, but may not appreciate how much power are in these two methods. For example, if you want to parse a string as an enum, it’s easy and works just like you’d expect from the numeric types: 1: string optionsString = "Persistent"; 2:  3: // can use Enum.Parse, which throws if finds something it doesn't like... 4: var result = (MessagingOptions)Enum.Parse(typeof (MessagingOptions), optionsString); 5:  6: if (result == MessagingOptions.Persistent) 7: { 8: Console.WriteLine("It worked!"); 9: } Note that Enum.Parse() will throw if it finds a value it doesn’t like.  But the values it likes are fairly flexible!  You can pass in a single value, or a comma separated list of values for flags and it will parse them all and set all bits: 1: // for string values, can have one, or comma separated. 2: string optionsString = "Persistent, Buffered"; 3:  4: var result = (MessagingOptions)Enum.Parse(typeof (MessagingOptions), optionsString); 5:  6: if (result.HasFlag(MessagingOptions.Persistent) && result.HasFlag(MessagingOptions.Buffered)) 7: { 8: Console.WriteLine("It worked!"); 9: } Or you can parse in a string containing a number that represents a single value or combination of values to set: 1: // 3 is the combination of Buffered (0x01) and Persistent (0x02) 2: var optionsString = "3"; 3:  4: var result = (MessagingOptions) Enum.Parse(typeof (MessagingOptions), optionsString); 5:  6: if (result.HasFlag(MessagingOptions.Persistent) && result.HasFlag(MessagingOptions.Buffered)) 7: { 8: Console.WriteLine("It worked again!"); 9: } And, if you really aren’t sure if the parse will work, and don’t want to handle an exception, you can use TryParse() instead: 1: string optionsString = "Persistent, Buffered"; 2: MessagingOptions result; 3:  4: // try parse returns true if successful, and takes an out parm for the result 5: if (Enum.TryParse(optionsString, out result)) 6: { 7: if (result.HasFlag(MessagingOptions.Persistent) && result.HasFlag(MessagingOptions.Buffered)) 8: { 9: Console.WriteLine("It worked!"); 10: } 11: } So we covered parsing a string to an enum, what about reversing that and converting an enum to a string?  The ToString() method is the obvious and most basic choice for most of us, but did you know you can pass a format string for enum types that dictate how they are written as a string?: 1: MessagingOptions value = MessagingOptions.Buffered | MessagingOptions.Persistent; 2:  3: // general format, which is the default, 4: Console.WriteLine("Default : " + value); 5: Console.WriteLine("G (default): " + value.ToString("G")); 6:  7: // Flags format, even if type does not have Flags attribute. 8: Console.WriteLine("F (flags) : " + value.ToString("F")); 9:  10: // integer format, value as number. 11: Console.WriteLine("D (num) : " + value.ToString("D")); 12:  13: // hex format, value as hex 14: Console.WriteLine("X (hex) : " + value.ToString("X")); Which displays: 1: Default : Buffered, Persistent 2: G (default): Buffered, Persistent 3: F (flags) : Buffered, Persistent 4: D (num) : 3 5: X (hex) : 00000003 Now, you may not really see a difference here between G and F because I used a [Flags] enum, the difference is that the “F” option treats the enum as if it were flags even if the [Flags] attribute is not present.  Let’s take a non-flags enum like the ResultCode used earlier: 1: // yes, we can do this even if it is not [Flags] enum. 2: ResultCode value = ResultCode.Warning | ResultCode.Error; And if we run that through the same formats again we get: 1: Default : 3 2: G (default): 3 3: F (flags) : Warning, Error 4: D (num) : 3 5: X (hex) : 00000003 Notice that since we had multiple values combined, but it was not a [Flags] marked enum, the G and default format gave us a number instead of a value name.  This is because the value was not a valid single-value constant of the enum.  However, using the F flags format string, it broke out the value into its component flags even though it wasn’t marked [Flags]. So, if you want to get an enum to display appropriately for whether or not it has the [Flags] attribute, use G which is the default.  If you always want it to attempt to break down the flags, use F.  For numeric output, obviously D or  X are the best choice depending on whether you want decimal or hex. Summary Hopefully, you learned a couple of new tricks with using the Enum class today!  I’ll add more little wonders as I think of them and thanks for all the invaluable input!   Technorati Tags: C#,.NET,Little Wonders,Enum,BlackRabbitCoder

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