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• Oracle nomeada pela Forrester Leader em Enterprise Business Intelligence Platforms

  - by Paulo Folgado

  According to an October 2010 report from independent analyst firm Forrester Research, Inc., Oracle is a leader in enterprise business intelligence (BI) platforms. Forrester Research defines BI as a set of methodologies, processes, architectures, and technologies that transform raw data into meaningful and useful information, which can then be used to enable more effective strategic, tactical, and operational insights and decision-making. Written by Forrester vice president and principal analyst Boris Evelson, The Forrester Wave: Enterprise Business Intelligence Platforms, Q4 2010 states that "Oracle has built new metadata-level [Oracle Business Intelligence Enterprise Edition 11g] integration with Oracle Fusion Middleware and Oracle Fusion Applications and continues to differentiate with its versatile ROLAP engine." The report goes on, "And in addition to closing some gaps it had in 10.x versions such as lack of RIA functionality, [the Oracle Business Intelligence Enterprise Edition 11g] actually leapfrogs the competition with the Common Enterprise Information Model (CEIM)--including the ability to define actions and execute processes right from BI metadata across BI and ERP applications." "We're pleased that the Forrester Wave recognizes Oracle Business Intelligence as a leading enterprise BI platform," said Paul Rodwick, vice president of product management, Oracle Business Intelligence. Key Innovations in Oracle Business Intelligence 11g Released in August 2010, Oracle Business Intelligence 11g represents the industry's most complete, integrated, and scalable suite of BI products. Encompassing thousands of new features and enhancements, the latest release offers three key areas of innovations. * A unified environment. The industry's first unified environment for accessing and analyzing data across relational, OLAP, and XML data sources. * Enhanced usability. A new, integrated scorecard application, plus innovations in reporting, visualization, search, and collaboration. * Enhanced performance, scalability, and security. Deeper integration with Oracle Enterprise Manager 11g and other components of Oracle Fusion Middleware provide lower management costs and increased performance, scalability, and security. Read the entire Forrester Wave Report.

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• Open Office APIs e Migração de Macros - 23/Fev/11

  - by Paulo Folgado

  AGENDAIntroduction on Oracle Open Office/OpenOffice.org API Oracle Open Office Basic IDE Hallo World and more Oracle Open Office dialog Programming Integrating Macros in Oracle Open Office Appetizer - Using JavaMicrosoft Office Macro MigrationEstimation Macro Migration effortMigrating Macros Migration pitfallsOs participantes deverão ter conhecimentos sólidos de Microsoft Office e de programação VBA.

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• Não perca esta semana: Oracle SOA Partner Community Forum Lisbon, Portugal - 21/Apr/10

  - by Paulo Folgado

  Mais informação sobre este evento aqui.

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• IIS permissions in C#

  - by Paulo

  Hello, I'm developing a solution in C# and I need to set permissions to some folders in the file system and in the Registry for IIS. Is there a way to give permitions to the file system and to the registry for the IIS users, that work for all IIs versions? For instance, in IIS 5 the user acount is ASPNET (I think that it has the IUSR_MachineName to), IIS 6 IUSR_MachineName and IIS 7 is IUSR. Thanks in advance, Paulo

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• running python script with cron

  - by paulo

  hey guys, im trying to run a python script after every 5 minutes using cron, inside the script is a django import import django when running the crontab i get mailed the following error ImportError: No module named django this is what the crontab file looks like: [email protected] */5 * * * * /usr/bin/python /Users/paulo/Desktop/ashtanga/ping/sender.py do anyone of you know whats causing this ? btw i do have django insalled version 1.2, python 2.6, and MacOX 10.6

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• SQL SERVER – Subquery or Join – Various Options – SQL Server Engine Knows the Best – Part 2

  - by pinaldave

  This blog post is part 2 of the earlier written article SQL SERVER – Subquery or Join – Various Options – SQL Server Engine knows the Best by Paulo R. Pereira. Paulo has left excellent comment to earlier article once again proving the point that SQL Server Engine is smart enough to figure out the best plan itself and uses the same for the query. Let us go over his comment as he has posted. “I think IN or EXISTS is the best choice, because there is a little difference between ‘Merge Join’ of query with JOIN (Inner Join) and the others options (Left Semi Join), and JOIN can give more results than IN or EXISTS if the relationship is 1:0..N and not 1:0..1. And if I try use NOT IN and NOT EXISTS the query plan is different from LEFT JOIN too (Left Anti Semi Join vs. Left Outer Join + Filter). So, I found a case where EXISTS has a different query plan than IN or ANY/SOME:” USE AdventureWorks GO -- use of SOME SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID = SOME ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) -- use of IN SELECT * FROM HumanResources.Employee E WHERE E.EmployeeID IN ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) -- use of EXISTS SELECT * FROM HumanResources.Employee E WHERE EXISTS ( SELECT EA.EmployeeID FROM HumanResources.EmployeeAddress EA UNION ALL SELECT EA.EmployeeID FROM HumanResources.EmployeeDepartmentHistory EA ) When looked into execution plan of the queries listed above indeed we do get different plans for queries and SQL Server Engines creates the best (least cost) plan for each query. Click on image to see larger images. Thanks Paulo for your wonderful contribution. Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, Readers Contribution, SQL, SQL Authority, SQL Joins, SQL Optimization, SQL Performance, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• UPK Basics Hands On Lab at Oracle Open World Latin America

  - by user581320

  Orrcle Open World Latin America 2012 will be in Sao Paulo, Brazil December fourth through the sixth. There's so much to see and learn from at Oracle OpenWorld : keynotes, technical sessions, Oracle and partner demonstrations, hands-on labs, networking events, and more.  I will be presenting a hands-on lab at the show this year, Introduction to Oracle User Productivity Kit - Learn the Basics in the afternoon on Tuesday December 4th.  This nonstop one hour lab covers topics from Getting Started with UPK to the basics of creating an outline, some typical content and concluding with publishing some of the many outputs UPK is capable of.   If you are planning on attending the show, come by the lab and see what UPK is all about.  I’ll be in Sao Paulo all week to fulfill my need to extend California’s summer by another week (trip bonus) and to meet and discuss all things UPK with our customers and partners.  If you’re not registered for the show there is still time. Check out the Oracle Open World Latin America 2012 web site for all the details. I look forward to seeing you in Sao Paulo!  Peter Maravelias Principal Product Strategy Manager, Oracle UPK 

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• A Panorama of JavaOne Latin America

  - by reza_rahman

  As you know, JavaOne Latin America 2012 was held at the Transamerica Expo Center in Sao Paulo, Brazil on December 4-6. It was a resounding success with a great vibe, excellent technical content and numerous world class speakers, both local and international. Various folks like Tori Wieldt, Steve Chin, Arun Gupta, Bruno Borges and myself looked at the conference from slightly different colored lenses. It's interesting to put them all together in a panoramatic collage: Tori wrote about the Sao Paulo Geek Bike Ride held the Saturday before the conference here (enjoy the photos and video). She also discusses the keynotes in great detail here. Steve looked at it from the viewpoint of someome instrumental to putting the event together. Read his thoughts here (he has more geek bike ride photos as well as material for his JavaFX/HTML 5 talk). Arun had a more holistic view of the conference. He covers the geek bike ride, the GlassFish party (organized by Bruno Borges), his Java EE talks, and more. Check out the cool photos as well as the technical material. Bruno provides the critical local perspective in his 7 reasons you had to be at JavaOne Latin America 2012. He discusses the OTN Lounge, the hands-on-lab, the Java community keynote, Java EE technical sessions and of course the GlassFish party! I covered the GlassFish booth, the lab and my technical sessions (as well as Sao Paulo's lively metal underground) here.

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• C# 4.0: Dynamic Programming

  - by Paulo Morgado

  The major feature of C# 4.0 is dynamic programming. Not just dynamic typing, but dynamic in broader sense, which means talking to anything that is not statically typed to be a .NET object. Dynamic Language Runtime The Dynamic Language Runtime (DLR) is piece of technology that unifies dynamic programming on the .NET platform, the same way the Common Language Runtime (CLR) has been a common platform for statically typed languages. The CLR always had dynamic capabilities. You could always use reflection, but its main goal was never to be a dynamic programming environment and there were some features missing. The DLR is built on top of the CLR and adds those missing features to the .NET platform. The Dynamic Language Runtime is the core infrastructure that consists of: Expression Trees The same expression trees used in LINQ, now improved to support statements. Dynamic Dispatch Dispatches invocations to the appropriate binder. Call Site Caching For improved efficiency. Dynamic languages and languages with dynamic capabilities are built on top of the DLR. IronPython and IronRuby were already built on top of the DLR, and now, the support for using the DLR is being added to C# and Visual Basic. Other languages built on top of the CLR are expected to also use the DLR in the future. Underneath the DLR there are binders that talk to a variety of different technologies: .NET Binder Allows to talk to .NET objects. JavaScript Binder Allows to talk to JavaScript in SilverLight. IronPython Binder Allows to talk to IronPython. IronRuby Binder Allows to talk to IronRuby. COM Binder Allows to talk to COM. Whit all these binders it is possible to have a single programming experience to talk to all these environments that are not statically typed .NET objects. The dynamic Static Type Let’s take this traditional statically typed code: Calculator calculator = GetCalculator(); int sum = calculator.Sum(10, 20); Because the variable that receives the return value of the GetCalulator method is statically typed to be of type Calculator and, because the Calculator type has an Add method that receives two integers and returns an integer, it is possible to call that Sum method and assign its return value to a variable statically typed as integer. Now lets suppose the calculator was not a statically typed .NET class, but, instead, a COM object or some .NET code we don’t know he type of. All of the sudden it gets very painful to call the Add method: object calculator = GetCalculator(); Type calculatorType = calculator.GetType(); object res = calculatorType.InvokeMember("Add", BindingFlags.InvokeMethod, null, calculator, new object[] { 10, 20 }); int sum = Convert.ToInt32(res); And what if the calculator was a JavaScript object? ScriptObject calculator = GetCalculator(); object res = calculator.Invoke("Add", 10, 20); int sum = Convert.ToInt32(res); For each dynamic domain we have a different programming experience and that makes it very hard to unify the code. With C# 4.0 it becomes possible to write code this way: dynamic calculator = GetCalculator(); int sum = calculator.Add(10, 20); You simply declare a variable who’s static type is dynamic. dynamic is a pseudo-keyword (like var) that indicates to the compiler that operations on the calculator object will be done dynamically. The way you should look at dynamic is that it’s just like object (System.Object) with dynamic semantics associated. Anything can be assigned to a dynamic. dynamic x = 1; dynamic y = "Hello"; dynamic z = new List<int> { 1, 2, 3 }; At run-time, all object will have a type. In the above example x is of type System.Int32. When one or more operands in an operation are typed dynamic, member selection is deferred to run-time instead of compile-time. Then the run-time type is substituted in all variables and normal overload resolution is done, just like it would happen at compile-time. The result of any dynamic operation is always dynamic and, when a dynamic object is assigned to something else, a dynamic conversion will occur. Code Resolution Method double x = 1.75; double y = Math.Abs(x); compile-time double Abs(double x) dynamic x = 1.75; dynamic y = Math.Abs(x); run-time double Abs(double x) dynamic x = 2; dynamic y = Math.Abs(x); run-time int Abs(int x) The above code will always be strongly typed. The difference is that, in the first case the method resolution is done at compile-time, and the others it’s done ate run-time. IDynamicMetaObjectObject The DLR is pre-wired to know .NET objects, COM objects and so forth but any dynamic language can implement their own objects or you can implement your own objects in C# through the implementation of the IDynamicMetaObjectProvider interface. When an object implements IDynamicMetaObjectProvider, it can participate in the resolution of how method calls and property access is done. The .NET Framework already provides two implementations of IDynamicMetaObjectProvider: DynamicObject : IDynamicMetaObjectProvider The DynamicObject class enables you to define which operations can be performed on dynamic objects and how to perform those operations. For example, you can define what happens when you try to get or set an object property, call a method, or perform standard mathematical operations such as addition and multiplication. ExpandoObject : IDynamicMetaObjectProvider The ExpandoObject class enables you to add and delete members of its instances at run time and also to set and get values of these members. This class supports dynamic binding, which enables you to use standard syntax like sampleObject.sampleMember, instead of more complex syntax like sampleObject.GetAttribute("sampleMember").

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• Is Your ASP.NET Development Server Not Working?

  - by Paulo Morgado

  Since Visual Studio 2005, Visual Studio comes with a development web server: the ASP.NET Development Server. I’ve been using this web server for simple test projects since than with Visual Studio 2005 and Visual Studio 2008 in Windows XP Professional on my work laptop and Windows XP Professional, Windows Vista 64bit Ultimate and Windows 7 64bit Ultimate at my home desktop without any problems (apart the known custom identity problem, that is). When I received my new work laptop, I installed Windows Vista 64bit Enterprise and Visual Studio 2008 and, for my surprise, the ASP.NET Development Server wasn’t working. I started looking for differences between the laptop environment and the desktop environment and the most notorious differences were: System Laptop Desktop SKU Windows Vista 64bit Enterprise Windows Vista 64bit Ultimate Joined to a Domain Yes No Anti-Virus McAffe ESET After asserting that no domain policies were being applied to my laptop and domain user and nothing was being logged by the ant-virus, my suspicions turned to the fact that the laptop was running an Enterprise SKU and the desktop was running an Ultimate SKU. After having problems with other applications I was sure that problem was the Enterprise SKU, but never found a solution to the problem. Because I wasn’t doing any web development at the time, I left it alone. After upgrading to Windows 7, the problem persisted but, because I wasn’t doing any web development at the time, once again, I left it alone. Now that I installed Visual Studio 2010 I had to solve this. After searching around forums and blogs that either didn’t offer an answer or offered very complicated workarounds that, sometimes, involved messing with the registry, I came to the conclusion that the solution is, in fact, very simple. When Windows Vista is installed, hosts file, according to this contains this definition: 127.0.0.1 localhost ::1 localhost This was not what I had on my laptop hosts file. What I had was this: #127.0.0.1 localhost #::1 localhost I might have changed it myself, but from the amount of people that I found complaining about this problem on Windows Vista, this was probably the way it was. The installation of Windows 7 leaves the hosts file like this: #127.0.0.1 localhost #::1 localhost And although the ASP.NET Development Server works fine on Windows 7 64bit Ultimate, on Windows 7 64bit Enterprise it needs to be change to this: 127.0.0.1 localhost ::1 localhost And I suspect it’s the same with Windows Vista 64bit Enterprise.

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• CodeIt.Right Code File Header Template For StyleCop Rules

  - by Paulo Morgado

  I like to use both StyleCop and CodeIt.Right to validate my code – StyleCop because it’s free and CodeIt.Right because it’s really good. While StyleCop provides only validation, CodeIt.Righ provides both validation and correction of violations. Unfortunately, CodeIt.Right’s supplied template for code file headers does not conform to StyleCop rules. Fortunately, CodeIt.Right allows us to define our own template. Here’s the one I use: <#@ template language="C#" #> //----------------------------------------------------------------------- // <copyright file="<#= System.IO.Path.GetFileName(Context.DestinationFile) #>" // project="<#= Context.ProjectName #>" // assembly="<#= Context.AssemblyName #>" // solution="<#= Context.SolutionName #>" // company="<#= Context.GetGlobalProperty("CompanyName") #>"> // Copyright (c) <#= Context.GetGlobalProperty("CompanyName") #>. All rights reserved. // </copyright> // <author id="<#= Context.GetGlobalProperty("UserID") #>"><#= Context.GetGlobalProperty("UserName") #></author> // <summary></summary> //-----------------------------------------------------------------------

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• Uploading documents to WSS (Windows Sharepoint Services) using SSIS

  - by Randy Aldrich Paulo

  Recently I was tasked to create an SSIS application that will query a database, split the results with certain criteria and create CSV file for every result and upload the file to a Sharepoint Document Library site. I've search the web and compiled the steps I've taken to build the solution. Summary: A) Create a proxy class of WSS Copy.asmx. B) Create a wrapper class for the proxy class and add a mechanism to check if the file is existing and delete method. C) Create an SSIS and call the wrapper class to transfer the files.   A) Creating Proxy Class 1) Go to Visual Studio Command Prompt type wsdl http://[sharepoint site]/_vti_bin/Copy.asmx this will generate the proxy class (Copy.cs) that will be added to the solution. 2) Add Copy.cs to solution and create another constructor for Copy() that will accept additional parameters url, userName, password and domain.   public Copy(string url, string userName, string password, string domain) { this.Url = url; this.Credentials = new System.Net.NetworkCredential(userName, password, domain); } 3) Add a namespace.     B) Wrapper Class Create a C# new library that references the Proxy Class.         C) Create SSIS SSIS solution is composed of:   1) Execute SQL Task, returns a single column rows containing the criteria. 2) Foreach Loop Container - loops per result from query (SQL Task) and creates a CSV file on a certain folder. 3) Script Task - calls the wrapper class to upload CSV files located on a certain folder to targer WSS Document Library Note: I've created another overload of CopyFiles that accepts a Directory Info instead of file location that loops thru the contents of the folder. Designer View Variable View

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• C# 4.0: Named And Optional Arguments

  - by Paulo Morgado

  As part of the co-evolution effort of C# and Visual Basic, C# 4.0 introduces Named and Optional Arguments. First of all, let’s clarify what are arguments and parameters: Method definition parameters are the input variables of the method. Method call arguments are the values provided to the method parameters. In fact, the C# Language Specification states the following on §7.5: The argument list (§7.5.1) of a function member invocation provides actual values or variable references for the parameters of the function member. Given the above definitions, we can state that: Parameters have always been named and still are. Parameters have never been optional and still aren’t. Named Arguments Until now, the way the C# compiler matched method call definition arguments with method parameters was by position. The first argument provides the value for the first parameter, the second argument provides the value for the second parameter, and so on and so on, regardless of the name of the parameters. If a parameter was missing a corresponding argument to provide its value, the compiler would emit a compilation error. For this call: Greeting("Mr.", "Morgado", 42); this method: public void Greeting(string title, string name, int age) will receive as parameters: title: “Mr.” name: “Morgado” age: 42 What this new feature allows is to use the names of the parameters to identify the corresponding arguments in the form: name:value Not all arguments in the argument list must be named. However, all named arguments must be at the end of the argument list. The matching between arguments (and the evaluation of its value) and parameters will be done first by name for the named arguments and than by position for the unnamed arguments. This means that, for this method definition: public static void Method(int first, int second, int third) this call declaration: int i = 0; Method(i, third: i++, second: ++i); will have this code generated by the compiler: int i = 0; int CS$0$0000 = i++; int CS$0$0001 = ++i; Method(i, CS$0$0001, CS$0$0000); which will give the method the following parameter values: first: 2 second: 2 third: 0 Notice the variable names. Although invalid being invalid C# identifiers, they are valid .NET identifiers and thus avoiding collision between user written and compiler generated code. Besides allowing to re-order of the argument list, this feature is very useful for auto-documenting the code, for example, when the argument list is very long or not clear, from the call site, what the arguments are. Optional Arguments Parameters can now have default values: public static void Method(int first, int second = 2, int third = 3) Parameters with default values must be the last in the parameter list and its value is used as the value of the parameter if the corresponding argument is missing from the method call declaration. For this call declaration: int i = 0; Method(i, third: ++i); will have this code generated by the compiler: int i = 0; int CS$0$0000 = ++i; Method(i, 2, CS$0$0000); which will give the method the following parameter values: first: 1 second: 2 third: 1 Because, when method parameters have default values, arguments can be omitted from the call declaration, this might seem like method overloading or a good replacement for it, but it isn’t. Although methods like this: public static StreamReader OpenTextFile( string path, Encoding encoding = null, bool detectEncoding = true, int bufferSize = 1024) allow to have its calls written like this: OpenTextFile("foo.txt", Encoding.UTF8); OpenTextFile("foo.txt", Encoding.UTF8, bufferSize: 4096); OpenTextFile( bufferSize: 4096, path: "foo.txt", detectEncoding: false); The complier handles default values like constant fields taking the value and useing it instead of a reference to the value. So, like with constant fields, methods with parameters with default values are exposed publicly (and remember that internal members might be publicly accessible – InternalsVisibleToAttribute). If such methods are publicly accessible and used by another assembly, those values will be hard coded in the calling code and, if the called assembly has its default values changed, they won’t be assumed by already compiled code. At the first glance, I though that using optional arguments for “bad” written code was great, but the ability to write code like that was just pure evil. But than I realized that, since I use private constant fields, it’s OK to use default parameter values on privately accessed methods.

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• C# Proposal: Compile Time Static Checking Of Dynamic Objects

  - by Paulo Morgado

  C# 4.0 introduces a new type: dynamic. dynamic is a static type that bypasses static type checking. This new type comes in very handy to work with: The new languages from the dynamic language runtime. HTML Document Object Model (DOM). COM objects. Duck typing … Because static type checking is bypassed, this: dynamic dynamicValue = GetValue(); dynamicValue.Method(); is equivalent to this: object objectValue = GetValue(); objectValue .GetType() .InvokeMember( "Method", BindingFlags.InvokeMethod, null, objectValue, null); Apart from caching the call site behind the scenes and some dynamic resolution, dynamic only looks better. Any typing error will only be caught at run time. In fact, if I’m writing the code, I know the contract of what I’m calling. Wouldn’t it be nice to have the compiler do some static type checking on the interactions with these dynamic objects? Imagine that the dynamic object that I’m retrieving from the GetValue method, besides the parameterless method Method also has a string read-only Property property. This means that, from the point of view of the code I’m writing, the contract that the dynamic object returned by GetValue implements is: string Property { get; } void Method(); Since it’s a well defined contract, I could write an interface to represent it: interface IValue { string Property { get; } void Method(); } If dynamic allowed to specify the contract in the form of dynamic(contract), I could write this: dynamic(IValue) dynamicValue = GetValue(); dynamicValue.Method(); This doesn’t mean that the value returned by GetValue has to implement the IValue interface. It just enables the compiler to verify that dynamicValue.Method() is a valid use of dynamicValue and dynamicValue.OtherMethod() isn’t. If the IValue interface already existed for any other reason, this would be fine. But having a type added to an assembly just for compile time usage doesn’t seem right. So, dynamic could be another type construct. Something like this: dynamic DValue { string Property { get; } void Method(); } The code could now be written like this; DValue dynamicValue = GetValue(); dynamicValue.Method(); The compiler would never generate any IL or metadata for this new type construct. It would only thee used for compile type static checking of dynamic objects. As a consequence, it makes no sense to have public accessibility, so it would not be allowed. Once again, if the IValue interface (or any other type definition) already exists, it can be used in the dynamic type definition: dynamic DValue : IValue, IEnumerable, SomeClass { string Property { get; } void Method(); } Another added benefit would be IntelliSense. I’ve been getting mixed reactions to this proposal. What do you think? Would this be useful?

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• Visual Studio 2010 Service Pack 1 And .NET Framework 4.0 Update

  - by Paulo Morgado

  As announced by Jason Zender in his blog post, Visual Studio 2010 Service Pack 1 is available for download for MSDN subscribers since March 8 and is available to the general public since March 10. Brian Harry provides information related to TFS and S. "Soma" Somasegar provides information on the latest Visual Studio 2010 enhancements. With this service pack for Visual Studio an update to the .NET Framework 4.0 is also released. For detailed information about these releases, please refer to the corresponding KB articles: Update for Microsoft .NET Framework 4 Description of Visual Studio 2010 Service Pack 1 Update: When I was upgrading from the Beta to the final release on Windows 7 Enterprise 64bit, the instalation hanged with Returning IDCANCEL. INSTALLMESSAGE_WARNING [Warning 1946.Property 'System.AppUserModel.ExcludeFromShowInNewInstall' for shortcut 'Manage Help Settings - ENU.lnk' could not be set.]. Canceling the installation didn’t work and I had to kill the setup.exe process. When reapplying it again, rollbacks were reported, so I reapplied it again – this time with succes.

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• LINQ: Single vs. First

  - by Paulo Morgado

  I’ve witnessed and been involved in several discussions around the correctness or usefulness of the Single method in the LINQ API. The most common argument is that you are querying for the first element on the result set and an exception will be thrown if there’s more than one element. The First method should be used instead, because it doesn’t throw if the result set has more than one item. Although the documentation for Single states that it returns a single, specific element of a sequence of values, it actually returns THE single, specific element of a sequence of ONE value. One you use the Single method in your code you are asserting that your query will result in a scalar result instead of a result set of arbitrary length. On the other hand, the documentation for First states that it returns the first element of a sequence of arbitrary length. Imagine you want to catch a taxi. You go the the taxi line and catch the FIRST one, no matter how many are there. On the other hand, if you go the the parking lot to get your car, you want the SINGLE one specific car that’s yours. If your “query” “returns” more than one car, it’s an exception. Either because it “returned” not only your car or you happen to have more than one car in that parking lot. In either case, you can only drive one car at once and you’ll need to refine your “query”.

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• C# 5.0 Async/Await Demo Code

  - by Paulo Morgado

  I’ve published the sample code I use to demonstrate the use of async/await in C# 5.0. You can find it here. Projects PauloMorgado.AyncDemo.WebServer This project is a simple web server implemented as a console application using Microsoft ASP.NET Web API self hosting and serves an image (with a delay) that is accessed by the other projects. This project has a dependency on Json.NET due to the fact the the Microsoft ASP.NET Web API hosting has a dependency on Json.NET. The application must be run on a command prompt with administrative privileges or a urlacl must be added to allow the use of the following command: netsh http add urlacl url=http://+:9090/ user=machine\username To remove the urlacl, just use the following command: netsh http delete urlacl url=http://+:9090/ PauloMorgado.AsyncDemo.WindowsForms This Windows Forms project contains three regions that must be uncommented one at a time: Sync with WebClient This code retrieves the image through a synchronous call using the WebClient class. Async with WebClient This code retrieves the image through an asynchronous call using the WebClient class. Async with HttpClient with cancelation This code retrieves the image through an asynchronous call with cancelation using the HttpClient class. PauloMorgado.AsyncDemo.Wpf This WPF project contains three regions that must be uncommented one at a time: Sync with WebClient This code retrieves the image through a synchronous call using the WebClient class. Async with WebClient This code retrieves the image through an asynchronous call using the WebClient class. Async with HttpClient with cancelation This code retrieves the image through an asynchronous call with cancelation using the HttpClient class.

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• Globalization, Localization And Why My Application Stopped Launching

  - by Paulo Morgado

  When I was localizing a Windows Phone application I was developing, I set the argument on the constructor of the AssemblyCultureAttribute for the neutral culture (en-US in this particular case) for my application. As it was late at night (or early in the dawn ) I went to sleep and, on the next day, the application wasn’t launching although it compiled just fine. I’ll have to confess that it took me a couple of nights to figure out what I had done to my application. Have you figured out what I did wrong? The documentation for the AssemblyCultureAttribute states that: The attribute is used by compilers to distinguish between a main assembly and a satellite assembly. A main assembly contains code and the neutral culture's resources. A satellite assembly contains only resources for a particular culture, as in [assembly:AssemblyCultureAttribute("de")]. Putting this attribute on an assembly and using something other than the empty string ("") for the culture name will make this assembly look like a satellite assembly, rather than a main assembly that contains executable code. Labeling a traditional code library with this attribute will break it, because no other code will be able to find the library's entry points at runtime. So, what I did was marking the once main assembly as a satellite assembly for the en-US culture which made it impossible to find its entry point. To set the the neutral culture for the assembly resources I should haveused (and eventually did) the NeutralResourcesLanguageAttribute. According to its documentation: The NeutralResourcesLanguageAttribute attribute informs the ResourceManager of the application's default culture, and also informs the ResourceManager that the default culture's resources are found in the main application assembly. When looking up resources in the same culture as the default culture, the ResourceManager automatically uses the resources located in the main assembly instead of searching for a satellite assembly. This improves lookup performance for the first resource you load, and can reduce your working set.

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• C# 4.0: Alternative To Optional Arguments

  - by Paulo Morgado

  Like I mentioned in my last post, exposing publicly methods with optional arguments is a bad practice (that’s why C# has resisted to having it, until now). You might argument that your method or constructor has to many variants and having ten or more overloads is a maintenance nightmare, and you’re right. But the solution has been there for ages: have an arguments class. The arguments class pattern is used in the .NET Framework is used by several classes, like XmlReader and XmlWriter that use such pattern in their Create methods, since version 2.0: XmlReaderSettings settings = new XmlReaderSettings(); settings.ValidationType = ValidationType.Auto; XmlReader.Create("file.xml", settings); With this pattern, you don’t have to maintain a long list of overloads and any default values for properties of XmlReaderSettings (or XmlWriterSettings for XmlWriter.Create) can be changed or new properties added in future implementations that won’t break existing compiled code. You might now argue that it’s too much code to write, but, with object initializers added in C# 3.0, the same code can be written like this: XmlReader.Create("file.xml", new XmlReaderSettings { ValidationType = ValidationType.Auto }); Looks almost like named and optional arguments, doesn’t it? And, who knows, in a future version of C#, it might even look like this: XmlReader.Create("file.xml", new { ValidationType = ValidationType.Auto });

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• C# 4.0: COM Interop Improvements

  - by Paulo Morgado

  Dynamic resolution as well as named and optional arguments greatly improve the experience of interoperating with COM APIs such as Office Automation Primary Interop Assemblies (PIAs). But, in order to alleviate even more COM Interop development, a few COM-specific features were also added to C# 4.0. Ommiting ref Because of a different programming model, many COM APIs contain a lot of reference parameters. These parameters are typically not meant to mutate a passed-in argument, but are simply another way of passing value parameters. Specifically for COM methods, the compiler allows to declare the method call passing the arguments by value and will automatically generate the necessary temporary variables to hold the values in order to pass them by reference and will discard their values after the call returns. From the point of view of the programmer, the arguments are being passed by value. This method call: object fileName = "Test.docx"; object missing = Missing.Value; document.SaveAs(ref fileName, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing, ref missing); can now be written like this: document.SaveAs("Test.docx", Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value, Missing.Value); And because all parameters that are receiving the Missing.Value value have that value as its default value, the declaration of the method call can even be reduced to this: document.SaveAs("Test.docx"); Dynamic Import Many COM methods accept and return variant types, which are represented in the PIAs as object. In the vast majority of cases, a programmer calling these methods already knows the static type of a returned object form the context of the call, but has to explicitly perform a cast on the returned values to make use of that knowledge. These casts are so common that they constitute a major nuisance. To make the developer’s life easier, it is now possible to import the COM APIs in such a way that variants are instead represented using the type dynamic which means that COM signatures have now occurrences of dynamic instead of object. This means that members of a returned object can now be easily accessed or assigned into a strongly typed variable without having to cast. Instead of this code: ((Excel.Range)(excel.Cells[1, 1])).Value2 = "Hello World!"; this code can now be used: excel.Cells[1, 1] = "Hello World!"; And instead of this: Excel.Range range = (Excel.Range)(excel.Cells[1, 1]); this can be used: Excel.Range range = excel.Cells[1, 1]; Indexed And Default Properties A few COM interface features are still not available in C#. On the top of the list are indexed properties and default properties. As mentioned above, these will be possible if the COM interface is accessed dynamically, but will not be recognized by statically typed C# code. No PIAs – Type Equivalence And Type Embedding For assemblies indentified with PrimaryInteropAssemblyAttribute, the compiler will create equivalent types (interfaces, structs, enumerations and delegates) and embed them in the generated assembly. To reduce the final size of the generated assembly, only the used types and their used members will be generated and embedded. Although this makes development and deployment of applications using the COM components easier because there’s no need to deploy the PIAs, COM component developers are still required to build the PIAs.

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• The Evolution Of C#

  - by Paulo Morgado

  The first release of C# (C# 1.0) was all about building a new language for managed code that appealed, mostly, to C++ and Java programmers. The second release (C# 2.0) was mostly about adding what wasn’t time to built into the 1.0 release. The main feature for this release was Generics. The third release (C# 3.0) was all about reducing the impedance mismatch between general purpose programming languages and databases. To achieve this goal, several functional programming features were added to the language and LINQ was born. Going forward, new trends are showing up in the industry and modern programming languages need to be more: Declarative With imperative languages, although having the eye on the what, programs need to focus on the how. This leads to over specification of the solution to the problem in hand, making next to impossible to the execution engine to be smart about the execution of the program and optimize it to run it more efficiently (given the hardware available, for example). Declarative languages, on the other hand, focus only on the what and leave the how to the execution engine. LINQ made C# more declarative by using higher level constructs like orderby and group by that give the execution engine a much better chance of optimizing the execution (by parallelizing it, for example). Concurrent Concurrency is hard and needs to be thought about and it’s very hard to shoehorn it into a programming language. Parallel.For (from the parallel extensions) looks like a parallel for because enough expressiveness has been built into C# 3.0 to allow this without having to commit to specific language syntax. Dynamic There was been lots of debate on which ones are the better programming languages: static or dynamic. The fact is that both have good qualities and users of both types of languages want to have it all. All these trends require a paradigm switch. C# is, in many ways, already a multi-paradigm language. It’s still very object oriented (class oriented as some might say) but it can be argued that C# 3.0 has become a functional programming language because it has all the cornerstones of what a functional programming language needs. Moving forward, will have even more. Besides the influence of these trends, there was a decision of co-evolution of the C# and Visual Basic programming languages. Since its inception, there was been some effort to position C# and Visual Basic against each other and to try to explain what should be done with each language or what kind of programmers use one or the other. Each language should be chosen based on the past experience and familiarity of the developer/team/project/company and not by particular features. In the past, every time a feature was added to one language, the users of the other wanted that feature too. Going forward, when a feature is added to one language, the other will work hard to add the same feature. This doesn’t mean that XML literals will be added to C# (because almost the same can be achieved with LINQ To XML), but Visual Basic will have auto-implemented properties. Most of these features require or are built on top of features of the .NET Framework and, the focus for C# 4.0 was on dynamic programming. Not just dynamic types but being able to talk with anything that isn’t a .NET class. Also introduced in C# 4.0 is co-variance and contra-variance for generic interfaces and delegates. Stay tuned for more on the new C# 4.0 features.

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• C# 4.0: Covariance And Contravariance In Generics Made Easy

  - by Paulo Morgado

  In my last post, I went through what is variance in .NET 4.0 and C# 4.0 in a rather theoretical way. Now, I’m going to try to make it a bit more down to earth. Given: class Base { } class Derived : Base { } Such that: Trace.Assert(typeof(Base).IsClass && typeof(Derived).IsClass && typeof(Base).IsGreaterOrEqualTo(typeof(Derived))); Covariance interface ICovariantIn<out T> { } Trace.Assert(typeof(ICovariantIn<Base>).IsGreaterOrEqualTo(typeof(ICovariantIn<Derived>))); Contravariance interface ICovariantIn<out T> { } Trace.Assert(typeof(IContravariantIn<Derived>).IsGreaterOrEqualTo(typeof(IContravariantIn<Base>))); Invariance interface IInvariantIn<T> { } Trace.Assert(!typeof(IInvariantIn<Base>).IsGreaterOrEqualTo(typeof(IInvariantIn<Derived>)) && !typeof(IInvariantIn<Derived>).IsGreaterOrEqualTo(typeof(IInvariantIn<Base>))); Where: public static class TypeExtensions { public static bool IsGreaterOrEqualTo(this Type self, Type other) { return self.IsAssignableFrom(other); } }

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• C# 4.0: Covariance And Contravariance In Generics

  - by Paulo Morgado

  C# 4.0 (and .NET 4.0) introduced covariance and contravariance to generic interfaces and delegates. But what is this variance thing? According to Wikipedia, in multilinear algebra and tensor analysis, covariance and contravariance describe how the quantitative description of certain geometrical or physical entities changes when passing from one coordinate system to another.(*) But what does this have to do with C# or .NET? In type theory, a the type T is greater (>) than type S if S is a subtype (derives from) T, which means that there is a quantitative description for types in a type hierarchy. So, how does covariance and contravariance apply to C# (and .NET) generic types? In C# (and .NET), variance applies to generic type parameters and not to the resulting generic type. A generic type parameter is: covariant if the ordering of the generic types follows the ordering of the generic type parameters: Generic<T> = Generic<S> for T = S. contravariant if the ordering of the generic types is reversed from the ordering of the generic type parameters: Generic<T> = Generic<S> for T = S. invariant if neither of the above apply. If this definition is applied to arrays, we can see that arrays have always been covariant because this is valid code: object[] objectArray = new string[] { "string 1", "string 2" }; objectArray[0] = "string 3"; objectArray[1] = new object(); However, when we try to run this code, the second assignment will throw an ArrayTypeMismatchException. Although the compiler was fooled into thinking this was valid code because an object is being assigned to an element of an array of object, at run time, there is always a type check to guarantee that the runtime type of the definition of the elements of the array is greater or equal to the instance being assigned to the element. In the above example, because the runtime type of the array is array of string, the first assignment of array elements is valid because string = string and the second is invalid because string = object. This leads to the conclusion that, although arrays have always been covariant, they are not safely covariant – code that compiles is not guaranteed to run without errors. In C#, the way to define that a generic type parameter as covariant is using the out generic modifier: public interface IEnumerable<out T> { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> { T Current { get; } bool MoveNext(); } Notice the convenient use the pre-existing out keyword. Besides the benefit of not having to remember a new hypothetic covariant keyword, out is easier to remember because it defines that the generic type parameter can only appear in output positions — read-only properties and method return values. In a similar way, the way to define a type parameter as contravariant is using the in generic modifier: public interface IComparer<in T> { int Compare(T x, T y); } Once again, the use of the pre-existing in keyword makes it easier to remember that the generic type parameter can only be used in input positions — write-only properties and method non ref and non out parameters. Because covariance and contravariance apply only to the generic type parameters, a generic type definition can have both covariant and contravariant generic type parameters in its definition: public delegate TResult Func<in T, out TResult>(T arg); A generic type parameter that is not marked covariant (out) or contravariant (in) is invariant. All the types in the .NET Framework where variance could be applied to its generic type parameters have been modified to take advantage of this new feature. In summary, the rules for variance in C# (and .NET) are: Variance in type parameters are restricted to generic interface and generic delegate types. A generic interface or generic delegate type can have both covariant and contravariant type parameters. Variance applies only to reference types; if you specify a value type for a variant type parameter, that type parameter is invariant for the resulting constructed type. Variance does not apply to delegate combination. That is, given two delegates of types Action<Derived> and Action<Base>, you cannot combine the second delegate with the first although the result would be type safe. Variance allows the second delegate to be assigned to a variable of type Action<Derived>, but delegates can combine only if their types match exactly. If you want to learn more about variance in C# (and .NET), you can always read: Covariance and Contravariance in Generics — MSDN Library Exact rules for variance validity — Eric Lippert Events get a little overhaul in C# 4, Afterward: Effective Events — Chris Burrows Note: Because variance is a feature of .NET 4.0 and not only of C# 4.0, all this also applies to Visual Basic 10.

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• LINQ: Enhancing Distinct With The PredicateEqualityComparer

  - by Paulo Morgado

  Today I was writing a LINQ query and I needed to select distinct values based on a comparison criteria. Fortunately, LINQ’s Distinct method allows an equality comparer to be supplied, but, unfortunately, sometimes, this means having to write custom equality comparer. Because I was going to need more than one equality comparer for this set of tools I was building, I decided to build a generic equality comparer that would just take a custom predicate. Something like this: public class PredicateEqualityComparer<T> : EqualityComparer<T> { private Func<T, T, bool> predicate; public PredicateEqualityComparer(Func<T, T, bool> predicate) : base() { this.predicate = predicate; } public override bool Equals(T x, T y) { if (x != null) { return ((y != null) && this.predicate(x, y)); } if (y != null) { return false; } return true; } public override int GetHashCode(T obj) { if (obj == null) { return 0; } return obj.GetHashCode(); } } Now I can write code like this: .Distinct(new PredicateEqualityComparer<Item>((x, y) => x.Field == y.Field)) But I felt that I’d lost all conciseness and expressiveness of LINQ and it doesn’t support anonymous types. So I came up with another Distinct extension method: public static IEnumerable<TSource> Distinct<TSource>(this IEnumerable<TSource> source, Func<TSource, TSource, bool> predicate) { return source.Distinct(new PredicateEqualityComparer<TSource>(predicate)); } And the query is now written like this: .Distinct((x, y) => x.Field == y.Field) Looks a lot better, doesn’t it?

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• TechDays 2010: What’s New On C# 4.0

  - by Paulo Morgado

  I would like to thank those that attended my session at TechDays 2010 and I hope that I was able to pass the message of what’s new on C#. For those that didn’t attend (or did and want to review it), the presentation can be downloaded from here. Code samples can be downlaoded from here. Here’s a list of resources mentioned on the session: The evolution of C# The Evolution Of C# Covariance and contravariance  C# 4.0: Covariance And Contravariance In Generics Covariance And Contravariance In Generics Made Easy Covarince and Contravariance in Generics Exact rules for variance validity Events get a little overhaul in C# 4, Afterward: Effective Events Named and optional arguments  Named And Optional Arguments Alternative To Optional Arguments Named and Optional Arguments (C# Programming Guide) Dynamic programming  Dynamic Programming C# Proposal: Compile Time Static Checking Of Dynamic Objects Using Type dynamic (C# Programming Guide) Dynamic Language Runtime Overview COM Interop Improvements COM Interop Improvements Type Equivalence and Embedded Interop Types Conclusion Visual C# Developer Center Visual C# 2010 Samples C# Language Specification 4.0 .NET Reflector LINQPad

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