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  • VS 2008 designer and usercontrol.

    - by Ram
    Hello, I have created a custom data grid control. I dragged it on windows form and set its properties like column and all & ran the project. It built successfully and I am able to view the grid control on the form. Now if i try to view that form in designer, I am getting following error.. Object reference not set to an instance of an object. Instances of this error (1) 1. Hide Call Stack at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.GetMemberTargetObject(XmlElementData xmlElementData, String& member) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.CreateAssignStatement(XmlElementData xmlElement) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.XmlElementData.get_CodeDomElement() at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.EndElement(String prefix, String name, String urn) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.Parse(XmlReader reader) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.ParseXml(String xmlStream, CodeStatementCollection statementCollection, String fileName, String methodName) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomParser.OnMethodPopulateStatements(Object sender, EventArgs e) at System.CodeDom.CodeMemberMethod.get_Statements() at System.ComponentModel.Design.Serialization.TypeCodeDomSerializer.Deserialize(IDesignerSerializationManager manager, CodeTypeDeclaration declaration) at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager manager) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager serializationManager) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.DeferredLoadHandler.Microsoft.VisualStudio.TextManager.Interop.IVsTextBufferDataEvents.OnLoadCompleted(Int32 fReload) If I ignore the exception, form appears blank with no sign of grid control on it. However I can see the code for the grid in the designer file. Any pointer on this would be a great help. I have customized grid for my custom requirements like I have added custom text box n all. I have defined 3 constructors public GridControl() public GridControl(IContainer container) protected GridControl(SerializationInfo info, StreamingContext context)

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  • Technical Article: Oracle Magazine Java Developer of the Year Adam Bien on Java EE 6 Simplicity by Design

    - by janice.heiss(at)oracle.com
    Java Champion and Oracle Magazine Java Developer of the Year, Adam Bien, offers his unique perspective on how to leverage new Java EE 6 features to build simple and maintainable applications in a new article in Oracle Magazine. Bien examines different Java EE 6 architectures and design approaches in an effort to help developers build efficient, simple, and maintainable applications.From the article: "Java EE 6 consists of a set of independent APIs released together under the Java EE name. Although these APIs are independent, they fit together surprisingly well. For a given application, you could use only JavaServer Faces (JSF) 2.0, you could use Enterprise JavaBeans (EJB) 3.1 for transactional services, or you could use Contexts and Dependency Injection (CDI) with Java Persistence API (JPA) 2.0 and the Bean Validation model to implement transactions.""With a pragmatic mix of available Java EE 6 APIs, you can entirely eliminate the need to implement infrastructure services such as transactions, threading, throttling, or monitoring in your application. The real challenge is in selecting the right subset of APIs that minimizes overhead and complexity while making sure you don't have to reinvent the wheel with custom code. As a general rule, you should strive to use existing Java SE and Java EE services before expanding your search to find alternatives." Read the entire article here.

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  • How to design highly scalable web services in Java?

    - by Kshitiz Sharma
    I am creating some Web Services that would have 2000 concurrent users. The services are offered for free and are hence expected to get a large user base. In the future it may be required to scale up to 50,000 users. There are already a few other questions that address the issue like - Building highly scalable web services However my requirements differ from the question above. For example - My application does not have a user interface, so images, CSS, javascript are not an issue. It is in Java so suggestions like using HipHop to translate PHP to native code are useless. Hence I decided to ask my question separately. This is my project setup - Rest based Web services using Apache CXF Hibernate 3.0 (With relevant optimizations like lazy loading and custom HQL for tune up) Tomcat 6.0 MySql 5.5 My questions are - Are there alternatives to Mysql that offer better performance for what I'm trying to do? What are some general things to abide by in order to scale a Java based web application? I am thinking of putting my Application in two tomcat instances with httpd redirecting the request to appropriate tomcat on basis of load. Is this the right approach? Separate tomcat instances can help but then database becomes the bottleneck since both applications access the same database? I am a programmer not a Db Admin, how difficult would it be to cluster a Mysql database (or, to cluster whatever database offered as an alternative to 1)? How effective are caching solutions like EHCache? Any other general best practices? Some clarifications - Could you partition the data? Yes we could but we're trying to avoid it. We need to run a lot of data mining algorithms and the design would evolve over time so we can't be sure what lines of partition should be there.

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  • What is the best approach for database design with lots of columns?

    - by Pratyush
    I am writing a query based financial application. It lets the user to write complicated equations (much like WHERE part of an SQL query) and find companies matching those criteria. For the above, I currently have more than 500 columns in the database table (each column representing a financial field). Example of Columns are: company_name, sales_annual_00, sales_annual_01, sales_annual_02, sales_annual_03, sales_annual_04, protit_annual_00, profit_annual1...(over 500 such columns). The number of rows is around 5000. Going forward, I would like to further increase the number of columns/financial-fields. For the above I would like to get help regarding: 1) What is the best database design approach? Is it ok to have these many number of columns? 2) How can it be normalized? (User can use any of these fields in search criteria). 3) Is it ok to stick with MySQL, or modern document based databases like MongoDB should be better for it? P.S. (Update): I have been using MySQL till now and a running example of the usage is at: http://screener.in/companies/89/Formula-- In above there around 500 fields/columns to create your query on, however, I seek to increase that number to much more in future.

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  • ODI 12c's Mapping Designer - Combining Flow Based and Expression Based Mapping

    - by Madhu Nair
    post by David Allan ODI is renowned for its declarative designer and minimal expression based paradigm. The new ODI 12c release has extended this even further to provide an extended declarative mapping designer. The ODI 12c mapper is a fusion of ODI's new declarative designer with the familiar flow based designer while retaining ODI’s key differentiators of: Minimal expression based definition, The ability to incrementally design an interface and to extract/load data from any combination of sources, and most importantly Backed by ODI’s extensible knowledge module framework. The declarative nature of the product has been extended to include an extensible library of common components that can be used to easily build simple to complex data integration solutions. Big usability improvements through consistent interactions of components and concepts all constructed around the familiar knowledge module framework provide the utmost flexibility. Here is a little taster: So what is a mapping? A mapping comprises of a logical design and at least one physical design, it may have many. A mapping can have many targets, of any technology and can be arbitrarily complex. You can build reusable mappings and use them in other mappings or other reusable mappings. In the example below all of the information from an Oracle bonus table and a bonus file are joined with an Oracle employees table before being written to a target. Some things that are cool include the one-click expression cross referencing so you can easily see what's used where within the design. The logical design in a mapping describes what you want to accomplish  (see the animated GIF here illustrating how the above mapping was designed) . The physical design lets you configure how it is to be accomplished. So you could have one logical design that is realized as an initial load in one physical design and as an incremental load in another. In the physical design below we can customize how the mapping is accomplished by picking Knowledge Modules, in ODI 12c you can pick multiple nodes (on logical or physical) and see common properties. This is useful as we can quickly compare property values across objects - below we can see knowledge modules settings on the access points between execution units side by side, in the example one table is retrieved via database links and the other is an external table. In the logical design I had selected an append mode for the integration type, so by default the IKM on the target will choose the most suitable/default IKM - which in this case is an in-built Oracle Insert IKM (see image below). This supports insert and select hints for the Oracle database (the ANSI SQL Insert IKM does not support these), so by default you will get direct path inserts with Oracle on this statement. In ODI 12c, the mapper is just that, a mapper. Design your mapping, write to multiple targets, the targets can be in the same data server, in different data servers or in totally different technologies - it does not matter. ODI 12c will derive and generate a plan that you can use or customize with knowledge modules. Some of the use cases which are greatly simplified include multiple heterogeneous targets, multi target inserts for Oracle and writing of XML. Let's switch it up now and look at a slightly different example to illustrate expression reuse. In ODI you can define reusable expressions using user functions. These can be reused across mappings and the implementations specialized per technology. So you can have common expressions across Oracle, SQL Server, Hive etc. shielding the design from the physical aspects of the generated language. Another way to reuse is within a mapping itself. In ODI 12c expressions can be defined and reused within a mapping. Rather than replicating the expression text in larger expressions you can decompose into smaller snippets, below you can see UNIT_TAX AMOUNT has been defined and is used in two downstream target columns - its used in the TOTAL_TAX_AMOUNT plus its used in the UNIT_TAX_AMOUNT (a recording of the calculation).  You can see the columns that the expressions depend on (upstream) and the columns the expression is used in (downstream) highlighted within the mapper. Also multi selecting attributes is a convenient way to see what's being used where, below I have selected the TOTAL_TAX_AMOUNT in the target datastore and the UNIT_TAX_AMOUNT in UNIT_CALC. You can now see many expressions at once now and understand much more at the once time without needlessly clicking around and memorizing information. Our mantra during development was to keep it simple and make the tool more powerful and do even more for the user. The development team was a fusion of many teams from Oracle Warehouse Builder, Sunopsis and BEA Aqualogic, debating and perfecting the mapper in ODI 12c. This was quite a project from supporting the capabilities of ODI in 11g to building the flow based mapping tool to support the future. I hope this was a useful insight, there is so much more to come on this topic, this is just a preview of much more that you will see of the mapper in ODI 12c.

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  • Oracle Develop 2011 - Moscow and Hyderabad Editions

    - by Cassandra Clark
    Connect with Oracle developers at Oracle Develop - Oracle Develop will be held in Moscow, April 12-13th, 2011 and again in Hyderabad, May 10th - 11th, 2011. Enjoy two days of technical content and hands-on learning focused on Oracle products and next-generation development trends and technologies, including rich enterprise applications (REAs), service-oriented architecture (SOA), and the database.Oracle Develop Moscow Tracks - Database DevelopmentApplication Infrastructure and Oracle WeblogicOracle Fusion Development and Rich Enterprise ApplicationsService Oriented ArchitectureOracle Develop Hyderabad Tracks - Application Grid and Oracle WeblogicDatabase DevelopmentOracle Fusion Development and Rich Enterprise ApplicationsService Oriented Architecture.NET with Oracle DatabaseRegister Now for Oracle Develop Moscow!Register Now for Oracle Develop Hyderabad!

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  • Register Game Object Components in Game Subsystems? (Component-based Game Object design)

    - by topright
    I'm creating a component-based game object system. Some tips: GameObject is simply a list of Components. There are GameSubsystems. For example, rendering, physics etc. Each GameSubsystem contains pointers to some of Components. GameSubsystem is a very powerful and flexible abstraction: it represents any slice (or aspect) of the game world. There is a need in a mechanism of registering Components in GameSubsystems (when GameObject is created and composed). There are 4 approaches: 1: Chain of responsibility pattern. Every Component is offered to every GameSubsystem. GameSubsystem makes a decision which Components to register (and how to organize them). For example, GameSubsystemRender can register Renderable Components. pro. Components know nothing about how they are used. Low coupling. A. We can add new GameSubsystem. For example, let's add GameSubsystemTitles that registers all ComponentTitle and guarantees that every title is unique and provides interface to quering objects by title. Of course, ComponentTitle should not be rewrited or inherited in this case. B. We can reorganize existing GameSubsystems. For example, GameSubsystemAudio, GameSubsystemRender, GameSubsystemParticleEmmiter can be merged into GameSubsystemSpatial (to place all audio, emmiter, render Components in the same hierarchy and use parent-relative transforms). con. Every-to-every check. Very innefficient. con. Subsystems know about Components. 2: Each Subsystem searches for Components of specific types. pro. Better performance than in Approach 1. con. Subsystems still know about Components. 3: Component registers itself in GameSubsystem(s). We know at compile-time that there is a GameSubsystemRenderer, so let's ComponentImageRender will call something like GameSubsystemRenderer::register(ComponentRenderBase*). pro. Performance. No unnecessary checks as in Approach 1. con. Components are badly coupled with GameSubsystems. 4: Mediator pattern. GameState (that contains GameSubsystems) can implement registerComponent(Component*). pro. Components and GameSubystems know nothing about each other. con. In C++ it would look like ugly and slow typeid-switch. Questions: Which approach is better and mostly used in component-based design? What Practice says? Any suggestions about implementation of Approach 4? Thank you.

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  • We need you! Sign up now to give Oracle your feedback on future product design trends at OpenWorld 2012

    - by mvaughan
    By Kathy Miedema, Oracle Applications User Experience Get the most from your Oracle OpenWorld 2012 experience and participate in a usability feedback session, where your expertise will help Oracle develop unbeatable products and solutions. Sign up to attend a one-hour session during Oracle OpenWorld. You’ll learn about Oracle’s future design trends -- including mobile applications and social networking -- and how these trends will affect your users down the road. A street scene from Oracle OpenWorld 2011. Oracle’s usability experts will guide you through practical learning sessions on the user experience of various business applications, middleware, and more. All user feedback sessions will be conducted October 1–3 at the InterContinental San Francisco Hotel on Howard Street, just a few steps away from the Moscone Center. To best match you with a user feedback activity, we will ask you about your role at your company. Our user feedback opportunities include focus groups, surveys, and one-on-one sessions with usability engineers. What do you get out of it? Customer and partner participants in the past have been surprised to learn how tuned in Oracle is to work that their applications users do every day. Oracle’s User Experience team members are trained to listen carefully, ask specific questions, interpret your answers, and work with designers to create products and solutions that suit your needs. Our goal is to help make you and your users more productive and efficient. Learn about Oracle’s process, and take advantage of the chance to give your specific feedback to the designers who create the enterprise applications of your future. See for yourself how Oracle collects feedback and measures its designs for turning them into code. Seats are limited for Oracle’s user feedback sessions, so sign up now by sending an e-mail to [email protected] with the subject line: Sign Me Up for an Oracle OpenWorld 2012 UX Session. For more information about customer feedback sessions and what you can learn from them, please visit the Usable Apps website. When: Monday-Wednesday during OpenWorld 2012, Oct. 1-3 Where: The InterContinental San Francisco Hotel How to sign up: RSVP now by sending an email to [email protected] with the subject line “Sign me up for an OOW 2012 UX Session.” Learn more: Visit the Usable Apps website at Get Involved.

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  • Functional vs. Non-Functional Requirements vs Design ideas in an SRS

    - by Nicholas Chow
    For a school project, I had to create a SRS for a "fictional" application. However they did not show us what it exactly entails, and were very vague with explanations. The SRS asked of us has to have at least 5 functional requirements, 5 non functional requirements and 1 constraint. Now I have tried my best to make one however I there are still some uncertainties left, I hope you experts can tell me whether or not I am thinking in the right direction. I will keep on updating this posts as I have questions regarding requirements that are vague to me, thank you all in advance for making SRS more clear for me FR1 Registration of Organizer FR1 describes the registration of an Organizer on CrowdFundum FR1.1 The system shall display a registration form on the website. FR1.2 The system shall require a Name, Username, Document number passport/ID card, Address, Zip code, City, Email address, Telephone number, Bank account, Captcha code on the registration form when a user registers. FR1.3 The system shall check whether the Name, Username, Document number passport/ID card, Address, Zip code, City, Email address, Telephone number, Bank account, Captcha code are filled out correctly within 1 seconds after a user submits the registration form. FR1.4 The system shall display an error message containing: “Registration could not be completed” to the subscriber within 1 seconds after the system check of the registration form was unsuccessful. FR1.5 The system shall send a verification email containing a verification link to the subscriber within 30 seconds after the system check of the registration form was successful. FR1.6 The system shall add the newly registered Organizer to the user base within 5 seconds after the verification link was accessed. Questions: FR1.1 Is this a functional requirement, or have I incorporated design idea in it by using "shall display on website". If so what would be a better way to write it? FR1.2 Is this better written in one requirement, or should I write each condition as a seperate requirement? FR1.3-1.5 Are these functional requirements or did I mix some non functional elements in it? How is it better phrased? FR1.3-1.6 Are these all correct functional requirements? As in free of ambiguity, complete, implementation free etc.

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  • How to handle authenticated user access to resources in document oriented system?

    - by Jeremy Raymond
    I'm developing a document oriented application and need to manage user access to the documents. I have a module that handles user authentication, and another module that handles document CRUD operations on the data store. Once a user is authenticated I need to enforce what operations the user can and cannot perform to documents based upon the user's permissions. The best option I could think of to integrate these two pieces together would be to create another module that duplicates the data API but that also takes the authenticated user as a parameter. The module would delegate the authorization check to the auth module and delegate the document operation to the data access module. Something like: -module(auth_data_access). % User is authenticated (logged into the system) % save_doc validates if user is allowed to save the given document and if so % saves it returning ok, else returns {error, permission_denied} save_doc(Doc, User) -> case auth:save_allowed(Doc, User) of ok -> data_access:save_doc(Doc); denied -> {error, permission_denied} end end. Is there a better way I can handle this?

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  • In which domains are message oriented middleware like AMQP useful?

    - by cocotwo
    What problem do MOM (Message Oriented Middleware) solve? Scalability? Integration? In which domain are they typically used and in which domains are they typically not used? For example, say, is Google using such solution for it's main search engine or to power GMail? What about big websites like Walmart, eBay, FedEx (pretty much a Java shop) and buy.com (pretty much an MS shop)? Does MOM solve a need there? Does it make any sense when you're writing a Webapp where you control the server-side and have an homogenous environment (say tens of Amazon EC2 instances all running Linux + Java JVMs) there and where the clients are, well, Web browsers? Does it make sense for desktop apps that need to communicate with a server? Or is it 'only' for big enterprise stuff where you typically have a happy mix of countless of different systems that needs to communicate in a way or another? I'm a bit confused as to what they're useful for and I think that with example of where they're appropriate and where they're not appropriate I could better understand their use.

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  • Looking for MSSQL Table Design Sanity Check for Profile Tables with Dynamic Columns.

    - by Code Sherpa
    I just want a general sanity check regarding database design. We are building a web system that has both Teachers and Students. Both have accounts in the system. Both have profiles in the system. My question is about the table design of those Profile tables. The Teacher profile is pretty static regarding the metadata associated with it. Each teacher has a set number of fields that exposes information about that individual (schools, degrees, etc). The students, however, are a different case. We are using a windows service to pull varying data about the students from an endless stream of excel spreadsheets. The data gets moved into our database and then the fields appear in association with the student's profile. Accordingly, each and every student may have very different fields in their profile. I originally started with the concept of three tables: Accounts ---------- AccountID TeacherProfiles ---------- TeacherProfileID AccountID SecondarySchool University YearsTeaching Etc... StudentProfiles ---------- StudentProfileID AccountID Header Value The StudentProfiles table would hold the name of the column headers from the excel spreadsheets and the associated values. I have since evolved the design a little to treat Profiles more generically per the attached ERD image. The Teacher and Student "Headers" are stored in a table called "ProfileAttributeTypes" and responses (either from the excel document or via input fields on the web form) are put in a ProfileAttributes table. This way both Student and Teacher profiles can be associated with a dynamic flow of profile fields. The "Permissions" table tells us whether we are dealing with a Student or a Teacher. Since this system is likely to grow quickly, I want to make sure the foundation is solid. Can you please provide feedback about this design and let me know if it seems sound or if you could see problems it might create and, if so, what might be a better approach? Thanks in advance.

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  • Web Safe Area (optimal resolution) for web app design?

    - by M.A.X
    I'm in the process of designing a new web app and I'm wondering for what 'Web Safe Area' should I optimize the app layout and design. By Web Safe Area I mean the actual area available to display the website in the browser (which is influenced by monitor resolution as well as the space taken up by the browser and OS) I did some investigation and thinking on my own but wanted to share this to see what the general opinion is. Here is what I found: Optimal Display Resolution: w3schools web stats seems to be the most referenced source (however they state that these are results from their site and is biased towards tech savvy users) http://www.w3counter.com/globalstats.php (aggregate data from something like 15,000 different sites that use their tracking services) StatCounter Global Stats Display Resolution (Stats are based on aggregate data collected by StatCounter on a sample exceeding 15 billion pageviews per month collected from across the StatCounter network of more than 3 million websites) NetMarketShare Screen Resolutions (marketshare.hitslink.com) (a web analytics consulting firm, they get data from browsers of site visitors to their on-demand network of live stats customers. The data is compiled from approximately 160 million visitors per month) Display Resolution Summary: There is a bit of variation between the above sources but in general as of Jan 2011 looks like 1024x768 is about 20%, while ~85% have a higher resolution of at least 1280x768 (1280x800 is the most common of these with 15-20% of total web, depending on the source; 1280x1024 and 1366x768 follow behind with 9-14% of the share). My guess would be that the higher resolution values will be even more common if we filter on North America, and even higher if we filter on N.American corporate users (unfortunately I couldn't find any free geographically filtered statistics). Another point to note is that the 1024x768 desktop user population is likely lower than the aforementioned 20%, seeing as the iPad (1024x768 native display) is likely propping up those number (the app I'm designing is flash based, Apple mobile devices don't support flash so iPad support isn't a concern). My recommendation would be to optimize around the 1280x768 constraint (*note: 1280x768 is actually a relatively rare resolution, but I think it's a valid constraint range considering that 1366x768 is relatively common and 1280 is the most common horizontal resolution). Browser + OS Constraints: To further add to the constraints we have to subtract the space taken up by the browser (assuming IE, which is the most space consuming) and the OS (assuming WinXP-Win7): Win7 has the biggest taskbar footprint at a height of 40px (XP's and Vista's is 30px) The default IE8 view uses up 25px at the bottom of the screen with the status bar and a further 120px at the top of the screen with the windows title bar and the browser UI (assuming the default 'favorites' toolbar is present, it would instead be 91px without the favorites toolbar). Assuming no scrollbar, we also loose a total of 4px horizontally for the window outline. This means that we are left with 583px of vertical space and 1276px of horizontal. In other words, a Web Safe Area of 1276 x 583 Is this a correct line of thinking? I'm really surprised that I couldn't find this type of investigation anywhere on the web. Lots of websites talk about designing for 1024x768, but that's only half the equation! There is no mention of browser/OS influences on the actual area you have to display the site/app. Any help on this would be greatly appreciated! Thanks. EDIT Another caveat to my line of thinking above is that different browsers actually take up different amounts of pixels based on the OS they're running on. For example, under WinXP IE8 takes up 142px on top of the screen (instead the aforementioned 120px for Win7) because the file menu shows up by default on XP while in Win7 the file menu is hidden by default. So it looks like on WinXP + IE8 the Web Safe Area would be a mere 572px (768px-142-30-24=572)

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  • How do I import a Flash Catalyst design into Dreamweaver?

    - by garrett
    So I made a banner in Flash Catalyst and published it to swf/air file. Now I can't find a way to get it into Dreamweaver. When I hit "Import SWF" and go to browse for it, it doesn't show up. When I publish it to swf, the file is a Jscript script file. I've been looking for tutorials, but I haven't found one for my issue. Currently I am downloading Flash Pro and hoping I can import the Catalyst design into that, then import the Flash Pro design of it into Dreamweaver. I am not very advanced in Catalyst or Dreamweaver, but I do know my way around a bit, and this is causing me one hell of a headache.

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  • C#: System.Lazy&lt;T&gt; and the Singleton Design Pattern

    - by James Michael Hare
    So we've all coded a Singleton at one time or another.  It's a really simple pattern and can be a slightly more elegant alternative to global variables.  Make no mistake, Singletons can be abused and are often over-used -- but occasionally you find a Singleton is the most elegant solution. For those of you not familiar with a Singleton, the basic Design Pattern is that a Singleton class is one where there is only ever one instance of the class created.  This means that constructors must be private to avoid users creating their own instances, and a static property (or method in languages without properties) is defined that returns a single static instance. 1: public class Singleton 2: { 3: // the single instance is defined in a static field 4: private static readonly Singleton _instance = new Singleton(); 5:  6: // constructor private so users can't instantiate on their own 7: private Singleton() 8: { 9: } 10:  11: // read-only property that returns the static field 12: public static Singleton Instance 13: { 14: get 15: { 16: return _instance; 17: } 18: } 19: } This is the most basic singleton, notice the key features: Static readonly field that contains the one and only instance. Constructor is private so it can only be called by the class itself. Static property that returns the single instance. Looks like it satisfies, right?  There's just one (potential) problem.  C# gives you no guarantee of when the static field _instance will be created.  This is because the C# standard simply states that classes (which are marked in the IL as BeforeFieldInit) can have their static fields initialized any time before the field is accessed.  This means that they may be initialized on first use, they may be initialized at some other time before, you can't be sure when. So what if you want to guarantee your instance is truly lazy.  That is, that it is only created on first call to Instance?  Well, there's a few ways to do this.  First we'll show the old ways, and then talk about how .Net 4.0's new System.Lazy<T> type can help make the lazy-Singleton cleaner. Obviously, we could take on the lazy construction ourselves, but being that our Singleton may be accessed by many different threads, we'd need to lock it down. 1: public class LazySingleton1 2: { 3: // lock for thread-safety laziness 4: private static readonly object _mutex = new object(); 5:  6: // static field to hold single instance 7: private static LazySingleton1 _instance = null; 8:  9: // property that does some locking and then creates on first call 10: public static LazySingleton1 Instance 11: { 12: get 13: { 14: if (_instance == null) 15: { 16: lock (_mutex) 17: { 18: if (_instance == null) 19: { 20: _instance = new LazySingleton1(); 21: } 22: } 23: } 24:  25: return _instance; 26: } 27: } 28:  29: private LazySingleton1() 30: { 31: } 32: } This is a standard double-check algorithm so that you don't lock if the instance has already been created.  However, because it's possible two threads can go through the first if at the same time the first time back in, you need to check again after the lock is acquired to avoid creating two instances. Pretty straightforward, but ugly as all heck.  Well, you could also take advantage of the C# standard's BeforeFieldInit and define your class with a static constructor.  It need not have a body, just the presence of the static constructor will remove the BeforeFieldInit attribute on the class and guarantee that no fields are initialized until the first static field, property, or method is called.   1: public class LazySingleton2 2: { 3: // because of the static constructor, this won't get created until first use 4: private static readonly LazySingleton2 _instance = new LazySingleton2(); 5:  6: // Returns the singleton instance using lazy-instantiation 7: public static LazySingleton2 Instance 8: { 9: get { return _instance; } 10: } 11:  12: // private to prevent direct instantiation 13: private LazySingleton2() 14: { 15: } 16:  17: // removes BeforeFieldInit on class so static fields not 18: // initialized before they are used 19: static LazySingleton2() 20: { 21: } 22: } Now, while this works perfectly, I hate it.  Why?  Because it's relying on a non-obvious trick of the IL to guarantee laziness.  Just looking at this code, you'd have no idea that it's doing what it's doing.  Worse yet, you may decide that the empty static constructor serves no purpose and delete it (which removes your lazy guarantee).  Worse-worse yet, they may alter the rules around BeforeFieldInit in the future which could change this. So, what do I propose instead?  .Net 4.0 adds the System.Lazy type which guarantees thread-safe lazy-construction.  Using System.Lazy<T>, we get: 1: public class LazySingleton3 2: { 3: // static holder for instance, need to use lambda to construct since constructor private 4: private static readonly Lazy<LazySingleton3> _instance 5: = new Lazy<LazySingleton3>(() => new LazySingleton3()); 6:  7: // private to prevent direct instantiation. 8: private LazySingleton3() 9: { 10: } 11:  12: // accessor for instance 13: public static LazySingleton3 Instance 14: { 15: get 16: { 17: return _instance.Value; 18: } 19: } 20: } Note, you need your lambda to call the private constructor as Lazy's default constructor can only call public constructors of the type passed in (which we can't have by definition of a Singleton).  But, because the lambda is defined inside our type, it has access to the private members so it's perfect. Note how the Lazy<T> makes it obvious what you're doing (lazy construction), instead of relying on an IL generation side-effect.  This way, it's more maintainable.  Lazy<T> has many other uses as well, obviously, but I really love how elegant and readable it makes the lazy Singleton.

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  • Should you remove all warnings in your Verilog or VHDL design? Wh or why not?

    - by Brian Carlton
    In (regular) software I have worked at companies where the gcc option -Wall is used to show all warnings. Then they need to be dealt with. With non-trivial FPGA/ASIC design in Verilog or VHDL there are often many many warnings. Should I worry about all of them? Do you have any specific techniques to suggest? My flow is mainly for FPGAs (Altera and Xilinx in particular), but I assume the same rules would apply to ASIC design, possibly more so due to the inability to change the design after it is built.

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  • Should you remove all warnings in your Verilog or VHDL design? Why or why not?

    - by Brian Carlton
    In (regular) software I have worked at companies where the gcc option -Wall is used to show all warnings. Then they need to be dealt with. With non-trivial FPGA/ASIC design in Verilog or VHDL there are often many many warnings. Should I worry about all of them? Do you have any specific techniques to suggest? My flow is mainly for FPGAs (Altera and Xilinx in particular), but I assume the same rules would apply to ASIC design, possibly more so due to the inability to change the design after it is built.

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  • Any advice about how to make the design of an application.

    - by VansFannel
    Hello. I want to design an application and I don't know where to start. I know I can use UML to design the application, but I don't know the steps I must follow. I've started doing the UML class diagram, but I suppose, I'm been doing the database model, not the class model for the application. If I don't explain it well, tell me. Is there any tutorial about how to design an application? Thank you.

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  • Delight and Excite

    - by Applications User Experience
    Mick McGee, CEO & President, EchoUser Editor’s Note: EchoUser is a User Experience design firm in San Francisco and a member of the Oracle Usability Advisory Board. Mick and his staff regularly consult on Oracle Applications UX projects. Being part of a user experience design firm, we have the luxury of working with a lot of great people across many great companies. We get to help people solve their problems.  At least we used to. The basic design challenge is still the same; however, the goal is not necessarily to solve “problems” anymore; it is, “I want our products to delight and excite!” The question for us as UX professionals is how to design to those goals, and then how to assess them from a usability perspective. I’m not sure where I first heard “delight and excite” (A book? blog post? Facebook  status? Steve Jobs quote?), but now I hear these listed as user experience goals all the time. In particular, somewhat paradoxically, I routinely hear them in enterprise software conversations. And when asking these same enterprise companies what will make the project successful, we very often hear, “Make it like Apple.” In past days, it was “make it like Yahoo (or Amazon or Google“) but now Apple is the common benchmark. Steve Jobs and Apple were not secrets, but with Jobs’ passing and Apple becoming the world’s most valuable company in the last year, the impact of great design and experience is suddenly very widespread. In particular, users’ expectations have gone way up. Being an enterprise company is no shield to the general expectations that users now have, for all products. Designing a “Minimum Viable Product” The user experience challenge has historically been, to echo the words of Eric Ries (author of Lean Startup) , to create a “minimum viable product”: the proverbial, “make it good enough”. But, in our profession, the “minimum viable” part of that phrase has oftentimes, unfortunately, referred to the design and user experience. Technology typically dominated the focus of the biggest, most successful companies. Few have had the laser focus of Apple to also create and sell design and user experience alongside great technology. But now that Apple is the most valuable company in the world, copying their success is a common undertaking. Great design is now a premium offering that everyone wants, from the one-person startup to the largest companies, consumer and enterprise. This emerging business paradigm will have significant impact across the user experience design process and profession. One area that particularly interests me is, how are we going to evaluate these new emerging “delight and excite” experiences, which are further customized to each particular domain? How to Measure “Delight and Excite” Traditional usability measures of task completion rate, assists, time, and errors are still extremely useful in many situations; however, they are too blunt to offer much insight into emerging experiences “Satisfaction” is usually assessed in user testing, in roughly equivalent importance to the above objective metrics. Various surveys and scales have provided ways to measure satisfying UX, with whatever questions they include. However, to meet the demands of new business goals and keep users at the center of design and development processes, we have to explore new methods to better capture custom-experience goals and emotion-driven user responses. We have had success assessing custom experiences, including “delight and excite”, by employing a variety of user testing methods that tend to combine formative and summative techniques (formative being focused more on identifying usability issues and ways to improve design, and summative focused more on metrics). Our most successful tool has been one we’ve been using for a long time, Magnitude Estimation Technique (MET). But it’s not necessarily about MET as a measure, rather how it is created. Caption: For one client, EchoUser did two rounds of testing.  Each test was a mix of performing representative tasks and gathering qualitative impressions. Each user participated in an in-person moderated 1-on-1 session for 1 hour, using a testing set-up where they held the phone. The primary goal was to identify usability issues and recommend design improvements. MET is based on a definition of the desired experience, which users will then use to rate items of interest (usually tasks in a usability test). In other words, a custom experience definition needs to be created. This can then be used to measure satisfaction in accomplishing tasks; “delight and excite”; or anything else from strategic goals, user demands, or elsewhere. For reference, our standard MET definition in usability testing is: “User experience is your perception of how easy to use, well designed and productive an interface is to complete tasks.” Articulating the User Experience We’ve helped construct experience definitions for several clients to better match their business goals. One example is a modification of the above that was needed for a company that makes medical-related products: “User experience is your perception of how easy to use, well-designed, productive and safe an interface is for conducting tasks. ‘Safe’ is how free an environment (including devices, software, facilities, people, etc.) is from danger, risk, and injury.” Another example is from a company that is pushing hard to incorporate “delight” into their enterprise business line: “User experience is your perception of a product’s ease of use and learning, satisfaction and delight in design, and ability to accomplish objectives.” I find the last one particularly compelling in that there is little that identifies the experience as being for a highly technical enterprise application. That definition could easily be applied to any number of consumer products. We have gone further than the above, including “sexy” and “cool” where decision-makers insisted they were part of the desired experience. We also applied it to completely different experiences where the “interface” was, for example, riding public transit, the “tasks” were train rides, and we followed the participants through the train-riding journey and rated various aspects accordingly: “A good public transportation experience is a cost-effective way of reliably, conveniently, and safely getting me to my intended destination on time.” To construct these definitions, we’ve employed both bottom-up and top-down approaches, depending on circumstances. For bottom-up, user inputs help dictate the terms that best fit the desired experience (usually by way of cluster and factor analysis). Top-down depends on strategic, visionary goals expressed by upper management that we then attempt to integrate into product development (e.g., “delight and excite”). We like a combination of both approaches to push the innovation envelope, but still be mindful of current user concerns. Hopefully the idea of crafting your own custom experience, and a way to measure it, can provide you with some ideas how you can adapt your user experience needs to whatever company you are in. Whether product-development or service-oriented, nearly every company is ultimately providing a user experience. The Bottom Line Creating great experiences may have been popularized by Steve Jobs and Apple, but I’ll be honest, it’s a good feeling to be moving from “good enough” to “delight and excite,” despite the challenge that entails. In fact, it’s because of that challenge that we will expand what we do as UX professionals to help deliver and assess those experiences. I’m excited to see how we, Oracle, and the rest of the industry will live up to that challenge.

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  • How to use CodeDomSerializer to serialize an object in .Net?

    - by user341127
    I have a class, which is defined as the following: [ToolboxItem(false)] [DesignTimeVisible(false)] [DesignerSerializer("DevExpress.XtraEditors.Design.RepositoryItemCodeDomSerializer, DevExpress.XtraEditors.v10.1.Design", "System.ComponentModel.Design.Serialization.CodeDomSerializer, System.Design")] [Designer("DevExpress.XtraEditors.Design.BaseRepositoryItemDesigner, DevExpress.XtraEditors.v10.1.Design")] [LicenseProvider(typeof(DXEditorLicenseProvider))] public class RepositoryItem : Component, ISupportInitialize, ICustomTypeDescriptor, IImageCollectionHelper {......} I tried the following code to serialize the object of this class. DesignerSerializationManager m = new System.ComponentModel.Design.Serialization.DesignerSerializationManager(); m.CreateSession(); DevExpress.XtraEditors.Design.RepositoryItemCodeDomSerializer s = m.GetSerializer(typeof(RepositoryItem), typeof(DevExpress.XtraEditors.Design.RepositoryItemCodeDomSerializer)) as DevExpress.XtraEditors.Design.RepositoryItemCodeDomSerializer; RepositoryItem i = persistentRepository1.Items[0]; //m.Container.Add(i); s.Serialize(m,i );// An error "Object reference not set to an instance of an object." happended here. For I am not familiar with CodeDom, I have spent one day to get the way out. I guess the above code has some stupid mistakes. Please give me a hand to show how to serialize AND DeSelialize such objects of the class of Repository. BTW, the reason I don't use any other serializer is that I am supposed not to have rights to know the source code of RepositoryItem and others could inherit RepositoryItem at the same time. And actually I have to deal with RepositoryItem and its descendants. Thank you in advance. Ying

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  • Visual Studio Designer looses / ignores data

    - by Kempeth
    I'm writing my own control - a datagridviewcolumn that displays integer values as texts like the comboboxcolumn can but without showing the combobox unless the cell is edited. I'm mostly there but I have problems with the databinding. I managed to get the necessary properties to appear in the designer but every time I set the datasource and close the editor the changes are dropped. When I assign the same datasource later in code it works like a charm, I just would prefer not having to do that... public class DataGridViewLookupColumn : DataGridViewColumn { private DataGridViewLookupCell template; private Object datasource = null; private String displaymember = String.Empty; private String valuemember = String.Empty; private BindingSource bindingsource = new BindingSource(); public DataGridViewLookupColumn() : base() { this.template = new DataGridViewLookupCell(); } public override DataGridViewCell CellTemplate { get { return this.template; } set { } } [Category("Data")] [ DefaultValue(null), RefreshProperties(RefreshProperties.Repaint), AttributeProvider(typeof(IListSource)), DesignerSerializationVisibility(DesignerSerializationVisibility.Visible), ] public object DataSource { get { return this.bindingsource.DataSource; //return this.datasource; } set { this.bindingsource.DataSource = value; this.bindingsource.EndEdit(); } } [Category("Data")] [ DefaultValue(""), TypeConverterAttribute("System.Windows.Forms.Design.DataMemberFieldConverter, System.Design"), Editor("System.Windows.Forms.Design.DataMemberFieldEditor, System.Design", typeof(System.Drawing.Design.UITypeEditor)), DesignerSerializationVisibility(DesignerSerializationVisibility.Visible), ] public String DisplayMember { get { return this.displaymember; } set { this.displaymember = value; } } [Category("Data")] [ DefaultValue(""), TypeConverterAttribute("System.Windows.Forms.Design.DataMemberFieldConverter, System.Design"), Editor("System.Windows.Forms.Design.DataMemberFieldEditor, System.Design", typeof(System.Drawing.Design.UITypeEditor)), DesignerSerializationVisibility(DesignerSerializationVisibility.Visible), ] public String ValueMember { get { return this.valuemember; } set { this.valuemember = value; } } } EDIT: I experimenting I just found out that that original DataGridViewComboBoxColumn can be made to behave exactly like I wanted to. By setting the DisplayStyle to Nothing the combobox control is only shown in edit mode.

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  • Visual Studio 2008 Report Server Project Design View not working.

    - by skynate
    When I create a new Reporting Services report or try to open an existing report (that has been working) in Visual Studio 2008. I cannot view the design. I get no error message and it only shows html code in the "Design View". I've tried reinstalling VS2008 and BIDS, but hasn't worked. This was all working when I last used it 2 weeks ago. -nate

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  • How to make msbuild ItemGroup items be separated with a space rather than semi-colon?

    - by mark
    Dear ladies and sirs. Observe the following piece of an msbuild script: <ItemGroup> <R Include="-Microsoft.Design#CA1000" /> <R Include="-Microsoft.Design#CA1002" /> </ItemGroup> I want to convert it to /ruleid:-Microsoft.Design#CA1000 /ruleid:-Microsoft.Design#CA1002 Now, the best I came up with is @(R -> '/ruleid:%(Identity)'), but this only yields /ruleid:-Microsoft.Design#CA1000;/ruleid:-Microsoft.Design#CA1002 Note the semi-colon separating the two rules, instead of a space. This is bad, it is not recognized by the fxcop - I need a space there. Now, this is a simple example, so I could just declare something like this: <PropertyGroup> <R>/ruleid:-Microsoft.Design#CA1000 /ruleid:-Microsoft.Design#CA1002</R </PropertyGroup> But, I do not like this, because in reality I have many rules I wish to disable and listing all of them like this is something I wish to avoid.

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