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  • Google attaque le FISC américain pour avoir trop payé d'impôts en 1984, il réclame le remboursement de plus de 80 millions de dollars de taxes

    Google attaque le FISC américain, il aurait payé trop d'impôts en 2004 Et lui réclame plus de 80 millions de dollarsGoogle vient d'entamer une procédure contre l'U.S. Internal Revenue Service, l'équivalent du FISC, pour récupérer 83.5 millions de dollars qui, d'après le géant d'Internet, lui seraient dûs.Le litige porte sur une opération boursière concernant des warrants (des bons de souscription à fort effet de levier, souvent qualifiés de spéculatifs) lors d'une transaction avec AOL.Les warrants sont des options d'achat - ou de vente - d'un produit sous-jacent (ici des actions de Google) qui permettent à leurs détenteurs (ici AOL) d'acheter - ou de vendre - ce sous-jacent à un prix fixe détermi...

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  • Making diff output more readable

    - by mgunes
    I'm looking for a tool that will take diff / debdiff output (and more specifically, the output of this script) and display the result of the comparison in a highly readable, graphical way. Any pointers would be appreciated. Ideally, it would be the GTK+, FOSS equivalent of MDR. Meld, Diffuse and similar software are not fit for this purpose, since they're intended to work standalone, and don't take input from stdin.

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  • How to navigate to connected iPhone? Filesystem path to `afc://`?

    - by Torben Gundtofte-Bruun
    When I connect my iPhone to Ubuntu 11.10, it gets automounted as afc://ca60751cc4b1ebb427c2f9da324914b0643a21f8/ and I can see that there are photos stored in afc://ca60751cc4b1ebb427c2f9da324914b0643a21f8/DCIM/103APPLE. I would like to use programs to access these photo files, but they don't accept the afc:// protocol -- they accept only normal file system paths. Is there a "normal file system equivalent" to afc:// paths?

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  • Why does Ubuntu 12.10 only see 8 cores?

    - by tunnuz
    In our lab we just bought a new machine with two 8-cores Intel(R) Xeon(R) CPU E5-2660 0 @ 2.20GHz processors which also support Hyper-Threading. I would expect Ubuntu to see 32 processing units, however it only detects 8 of them (the equivalent of just one processor with Hyper-Threading disabled). The bios correctly reports a total of 32 processing units. I am using Ubuntu 12.10 desktop 32 bit. Any idea about how to solve this?

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  • Video playback in games - formats & decoding

    - by snake5
    What free / non-restrictive open-source solutions (not GPL) are available for decoding game videos? The requirements are simple: a relatively easy to use C API encoded files must be quite small there must be an application that converts videos from any format (whatever codec is installed on Windows or equivalent amount of internally decoded formats) decoding has to happen fairly quickly bonus points go to file formats that are popular / actively supported and developed

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  • Canonical tags for separate mobile URLs

    - by DnBase
    I have a Drupal website serving mobile pages from different urls (starting from /mobile). According to Google recommendations I should use the canonical tag to map desktop and mobile pages. Right now I did this in case I serve the same node (e.g: node/123 and mobile/node/123) but should I do this for other pages as well that are equivalent but share a different content? For example do I need to map the desktop and mobile homepages even if they don't have the same content at all?

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  • WPF4 Unleashed - how does converting child elements work?

    - by Kapol
    In chapter 2 of the book WPF4 Unleashed the author shows an example of how XAML processes type conversion. He states that <SolidColorBrush>White</SolidColorBrush> is equivalent to <SolidColorBrush Color="White"/> , because a string can be converted into a SolidColorBrush object. But how is that enough? It doesn't make sense to me. How does XAML know to which property should the value White be assigned?

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  • How can I get rid of just the untracked files in git?

    - by dukeofgaming
    In Mercurial I can do this with the bundled Purge Extension and executing the following command: hg purge Also good to get rid of ignored files: hg purge --all I'm curious about the most practical/used equivalent solution in git. Edit: I want to just get rid of the untracked files, not reset everything (e.g. suppose I have a program generating cache files or generated code and I want to delete them with git's help)

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  • Google présente Body Browser, un explorateur du corps humain basé sur WebGL et l'expérience utilisateur de Google Earth

    Google présente « Body Browser », un explorateur du corps humain basé sur WebGL Et inspiré de l'expérience utilisateur de Google Earth Voilà une nouvelle qui devrait ravir les chercheurs et étudiants en sciences médicales. Google travaille sur un équivalent de Google Earth, qui permet, via les navigateurs supportant WebGL, d'explorer, zoomer et détailler les différents compartiments, organes ou tissus du corps humain. L'application dispose d'une barre de recherche et d'un système de navigation très similaire à celui de Google Earth, ce qui devrait faciliter sa prise en main à la sortie du produit ...

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  • SEO and Increasing Website Traffic

    In today's modern world, a website is the equivalent of a huge billboard outside your office. It is your advertising window to all your customers and you want people to see it. There is not much point in having an all singing, all dancing website that nobody visits!

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  • SEO and Increasing Website Traffic

    In today's modern world, a website is the equivalent of a huge billboard outside your office. It is your advertising window to all your customers and you want people to see it. There is not much point in having an all singing, all dancing website that nobody visits!

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  • How does the ETVDX model fit in with project management?

    - by peter_gent
    In a lecture, the lecturer described the following model : E - entry (the preconditions to a task). T - task - doing the task V - verifying the tasks quality D - Delivering the tasks X - Exit. or ETVDX If anyone is familiar with this 'generic compliance model', how does it fit into software development exactly? I presume it's equivalent to the waterfall model of negotiating requirements defining/decompose stage estimating effort estimating resources developing schedule.

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  • Automated software installation for MS Windows?

    - by Duncan Bayne
    I am currently setting up a Windows development environment (the whole Visual Studio 2010 stack plus plugins on top of Windows 7). This has got me wondering whether there's a Windows equivalent to what I do for dev environment setup in Ubuntu. It takes literally hours to get a dev environment set up in Windows, involving a lot of manual intervention. On Ubuntu, I have two shell scripts - one I run as root which configures the system using apt-get (amongst other things), one I run as me which configures my user account. Those scripts live in my private Subversion repository. To set up a dev environment from scratch requires five commands: sudo apt-get install -y subversion svn co http://svn.XXXX.XXX/personal/ cd personal sudo ./ubuntu_setup_root.sh ./ubuntu_setup_user.sh The only human intervention required is to pick a root password for MySQL. So it takes only a few minutes of human attention to go from a vanilla Ubuntu installation to a full development environment with the latest builds of everything, perfectly tailored down to shortcut keys and wallpaper. Is there an equivalent process for Windows? In an ideal world it'd be something trivially scriptable using C# Script or Powershell, which could live in source control & make use of a repository of ISOs downloaded from MSDN ...

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  • Mac OS X Lion (10.7) Drive Encryption

    - by Skoota
    My iMac has two drives (a 256 GB solid-state drive, and regular 2 TB hard drive). The Mac OS X Lion system is installed on the solid-state drive and, like many other users, I have moved my user profile folder onto the secondary 2 TB drive. However, as you may be aware, FileVault 2 on Mac OS X Lion (10.7) only encrypts the system drive. This leaves my data drive (containing my user profile folder, with all of my data) unencrypted. I am aware that work arounds for this issue exist (such as https://github.com/jridgewell/Unlock) but I am not happy with the results since they involve decrypting the data drive on startup using a LaunchDaemon (before any users have logged into the computer) essentially meaning that any user who logs onto the computer will see the unencrypted drive. I would like a method which will only unencrypted the data when an authorised user logs into the computer. As such, is there a way to do one of the following? Encrypt the entire data drive and only decrypt the drive when an authorised user logs into the computer. This would be equivalent behaviour to the Lion FileVault 2 feature, but on a secondary drive rather than the system drive. Encrypt only the user profile folder on the data drive, and only decrypt the folder when the user logs into the computer. This would be equivalent to the behaviour of FileVault 1 on previous versions of Mac OS X? I am happy to pay for a commercial third-party product that provides the required feature(s), but I have not yet been able to find one. Thanks in advance for any assistance.

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  • How can I both pipe and display output in Windows' command line?

    - by Bob
    I have a process I need to run within a batch file. This process produces some output. I need to both display this output to the screen and send (pipe) it to another program. The bash method uses tee: echo 'ee' | tee /dev/tty | foo Is there an equivalent for Windows? I am happy to use PowerShell if necessary. There are tee ports for Windows, but there does not appear to be an equivalent for /dev/tty, which complicates matters. The specific use-case here: I have a program (launch4j) that I need to run, displaying output to the user. At the same time, I need to be able to detect success or failure in the script. Unfortunately, this program does not set an exit code, and I cannot force it to do so. My current workaround involves piping to find, to search the output (launch4j config.xml | find "Successfully created") - however, that swallows the output I need to display. Therefore, I need some way to both display to the screen and send the ouput to a command - and this command should be able to set ERRORLEVEL (it cannot run asynchronously).

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  • Prevent Outlook 2010 Insert Picture resizing image

    - by Rup
    When I "Insert Picture" a JPEG in Outlook 2010 it automatically resizes the image and, I think, recompresses it too. I realise this would be useful for photographs or for people who try to email 1MB BMPs but I would like to email around an image at the original pixel size without recompression. Is there a way to turn this off, or better still choose settings for each image insert? I found this page in the Office help. It's for Word, PowerPoint and Excel not Outlook but points you at File, Options, Advanced, Image Settings. There's no equivalent section in Outlook. I know Outlook uses Word as its editor so I've looked at Word's settings but there isn't an 'original size' here: there's only 'turn off image recompression' and pick target DPI from 96, 150, 220. I guess Office is finding a DPI value in the JPEG file and scaling it up or down to match this setting. I can't find an equivalent option in Outlook's options menu but there's so many settings and pop-up dialogs I may have missed something. Picture Format, Reset image size resets the image to the rescaled version, not the original. I can't see a way to edit a pixel value into size values in the image properties after insert. Thanks! I realise I can probably achieve this by editing the image metadata in PhotoShop elements or similar but there ought to be a way without editing the file? This is new behaviour in Outlook 2010; 2007 didn't do this.

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  • New features of C# 4.0

    This article covers New features of C# 4.0. Article has been divided into below sections. Introduction. Dynamic Lookup. Named and Optional Arguments. Features for COM interop. Variance. Relationship with Visual Basic. Resources. Other interested readings… 22 New Features of Visual Studio 2008 for .NET Professionals 50 New Features of SQL Server 2008 IIS 7.0 New features Introduction It is now close to a year since Microsoft Visual C# 3.0 shipped as part of Visual Studio 2008. In the VS Managed Languages team we are hard at work on creating the next version of the language (with the unsurprising working title of C# 4.0), and this document is a first public description of the planned language features as we currently see them. Please be advised that all this is in early stages of production and is subject to change. Part of the reason for sharing our plans in public so early is precisely to get the kind of feedback that will cause us to improve the final product before it rolls out. Simultaneously with the publication of this whitepaper, a first public CTP (community technology preview) of Visual Studio 2010 is going out as a Virtual PC image for everyone to try. Please use it to play and experiment with the features, and let us know of any thoughts you have. We ask for your understanding and patience working with very early bits, where especially new or newly implemented features do not have the quality or stability of a final product. The aim of the CTP is not to give you a productive work environment but to give you the best possible impression of what we are working on for the next release. The CTP contains a number of walkthroughs, some of which highlight the new language features of C# 4.0. Those are excellent for getting a hands-on guided tour through the details of some common scenarios for the features. You may consider this whitepaper a companion document to these walkthroughs, complementing them with a focus on the overall language features and how they work, as opposed to the specifics of the concrete scenarios. C# 4.0 The major theme for C# 4.0 is dynamic programming. Increasingly, objects are “dynamic” in the sense that their structure and behavior is not captured by a static type, or at least not one that the compiler knows about when compiling your program. Some examples include a. objects from dynamic programming languages, such as Python or Ruby b. COM objects accessed through IDispatch c. ordinary .NET types accessed through reflection d. objects with changing structure, such as HTML DOM objects While C# remains a statically typed language, we aim to vastly improve the interaction with such objects. A secondary theme is co-evolution with Visual Basic. Going forward we will aim to maintain the individual character of each language, but at the same time important new features should be introduced in both languages at the same time. They should be differentiated more by style and feel than by feature set. The new features in C# 4.0 fall into four groups: Dynamic lookup Dynamic lookup allows you to write method, operator and indexer calls, property and field accesses, and even object invocations which bypass the C# static type checking and instead gets resolved at runtime. Named and optional parameters Parameters in C# can now be specified as optional by providing a default value for them in a member declaration. When the member is invoked, optional arguments can be omitted. Furthermore, any argument can be passed by parameter name instead of position. COM specific interop features Dynamic lookup as well as named and optional parameters both help making programming against COM less painful than today. On top of that, however, we are adding a number of other small features that further improve the interop experience. Variance It used to be that an IEnumerable<string> wasn’t an IEnumerable<object>. Now it is – C# embraces type safe “co-and contravariance” and common BCL types are updated to take advantage of that. Dynamic Lookup Dynamic lookup allows you a unified approach to invoking things dynamically. With dynamic lookup, when you have an object in your hand you do not need to worry about whether it comes from COM, IronPython, the HTML DOM or reflection; you just apply operations to it and leave it to the runtime to figure out what exactly those operations mean for that particular object. This affords you enormous flexibility, and can greatly simplify your code, but it does come with a significant drawback: Static typing is not maintained for these operations. A dynamic object is assumed at compile time to support any operation, and only at runtime will you get an error if it wasn’t so. Oftentimes this will be no loss, because the object wouldn’t have a static type anyway, in other cases it is a tradeoff between brevity and safety. In order to facilitate this tradeoff, it is a design goal of C# to allow you to opt in or opt out of dynamic behavior on every single call. The dynamic type C# 4.0 introduces a new static type called dynamic. When you have an object of type dynamic you can “do things to it” that are resolved only at runtime: dynamic d = GetDynamicObject(…); d.M(7); The C# compiler allows you to call a method with any name and any arguments on d because it is of type dynamic. At runtime the actual object that d refers to will be examined to determine what it means to “call M with an int” on it. The type dynamic can be thought of as a special version of the type object, which signals that the object can be used dynamically. It is easy to opt in or out of dynamic behavior: any object can be implicitly converted to dynamic, “suspending belief” until runtime. Conversely, there is an “assignment conversion” from dynamic to any other type, which allows implicit conversion in assignment-like constructs: dynamic d = 7; // implicit conversion int i = d; // assignment conversion Dynamic operations Not only method calls, but also field and property accesses, indexer and operator calls and even delegate invocations can be dispatched dynamically: dynamic d = GetDynamicObject(…); d.M(7); // calling methods d.f = d.P; // getting and settings fields and properties d[“one”] = d[“two”]; // getting and setting thorugh indexers int i = d + 3; // calling operators string s = d(5,7); // invoking as a delegate The role of the C# compiler here is simply to package up the necessary information about “what is being done to d”, so that the runtime can pick it up and determine what the exact meaning of it is given an actual object d. Think of it as deferring part of the compiler’s job to runtime. The result of any dynamic operation is itself of type dynamic. Runtime lookup At runtime a dynamic operation is dispatched according to the nature of its target object d: COM objects If d is a COM object, the operation is dispatched dynamically through COM IDispatch. This allows calling to COM types that don’t have a Primary Interop Assembly (PIA), and relying on COM features that don’t have a counterpart in C#, such as indexed properties and default properties. Dynamic objects If d implements the interface IDynamicObject d itself is asked to perform the operation. Thus by implementing IDynamicObject a type can completely redefine the meaning of dynamic operations. This is used intensively by dynamic languages such as IronPython and IronRuby to implement their own dynamic object models. It will also be used by APIs, e.g. by the HTML DOM to allow direct access to the object’s properties using property syntax. Plain objects Otherwise d is a standard .NET object, and the operation will be dispatched using reflection on its type and a C# “runtime binder” which implements C#’s lookup and overload resolution semantics at runtime. This is essentially a part of the C# compiler running as a runtime component to “finish the work” on dynamic operations that was deferred by the static compiler. Example Assume the following code: dynamic d1 = new Foo(); dynamic d2 = new Bar(); string s; d1.M(s, d2, 3, null); Because the receiver of the call to M is dynamic, the C# compiler does not try to resolve the meaning of the call. Instead it stashes away information for the runtime about the call. This information (often referred to as the “payload”) is essentially equivalent to: “Perform an instance method call of M with the following arguments: 1. a string 2. a dynamic 3. a literal int 3 4. a literal object null” At runtime, assume that the actual type Foo of d1 is not a COM type and does not implement IDynamicObject. In this case the C# runtime binder picks up to finish the overload resolution job based on runtime type information, proceeding as follows: 1. Reflection is used to obtain the actual runtime types of the two objects, d1 and d2, that did not have a static type (or rather had the static type dynamic). The result is Foo for d1 and Bar for d2. 2. Method lookup and overload resolution is performed on the type Foo with the call M(string,Bar,3,null) using ordinary C# semantics. 3. If the method is found it is invoked; otherwise a runtime exception is thrown. Overload resolution with dynamic arguments Even if the receiver of a method call is of a static type, overload resolution can still happen at runtime. This can happen if one or more of the arguments have the type dynamic: Foo foo = new Foo(); dynamic d = new Bar(); var result = foo.M(d); The C# runtime binder will choose between the statically known overloads of M on Foo, based on the runtime type of d, namely Bar. The result is again of type dynamic. The Dynamic Language Runtime An important component in the underlying implementation of dynamic lookup is the Dynamic Language Runtime (DLR), which is a new API in .NET 4.0. The DLR provides most of the infrastructure behind not only C# dynamic lookup but also the implementation of several dynamic programming languages on .NET, such as IronPython and IronRuby. Through this common infrastructure a high degree of interoperability is ensured, but just as importantly the DLR provides excellent caching mechanisms which serve to greatly enhance the efficiency of runtime dispatch. To the user of dynamic lookup in C#, the DLR is invisible except for the improved efficiency. However, if you want to implement your own dynamically dispatched objects, the IDynamicObject interface allows you to interoperate with the DLR and plug in your own behavior. This is a rather advanced task, which requires you to understand a good deal more about the inner workings of the DLR. For API writers, however, it can definitely be worth the trouble in order to vastly improve the usability of e.g. a library representing an inherently dynamic domain. Open issues There are a few limitations and things that might work differently than you would expect. · The DLR allows objects to be created from objects that represent classes. However, the current implementation of C# doesn’t have syntax to support this. · Dynamic lookup will not be able to find extension methods. Whether extension methods apply or not depends on the static context of the call (i.e. which using clauses occur), and this context information is not currently kept as part of the payload. · Anonymous functions (i.e. lambda expressions) cannot appear as arguments to a dynamic method call. The compiler cannot bind (i.e. “understand”) an anonymous function without knowing what type it is converted to. One consequence of these limitations is that you cannot easily use LINQ queries over dynamic objects: dynamic collection = …; var result = collection.Select(e => e + 5); If the Select method is an extension method, dynamic lookup will not find it. Even if it is an instance method, the above does not compile, because a lambda expression cannot be passed as an argument to a dynamic operation. There are no plans to address these limitations in C# 4.0. Named and Optional Arguments Named and optional parameters are really two distinct features, but are often useful together. Optional parameters allow you to omit arguments to member invocations, whereas named arguments is a way to provide an argument using the name of the corresponding parameter instead of relying on its position in the parameter list. Some APIs, most notably COM interfaces such as the Office automation APIs, are written specifically with named and optional parameters in mind. Up until now it has been very painful to call into these APIs from C#, with sometimes as many as thirty arguments having to be explicitly passed, most of which have reasonable default values and could be omitted. Even in APIs for .NET however you sometimes find yourself compelled to write many overloads of a method with different combinations of parameters, in order to provide maximum usability to the callers. Optional parameters are a useful alternative for these situations. Optional parameters A parameter is declared optional simply by providing a default value for it: public void M(int x, int y = 5, int z = 7); Here y and z are optional parameters and can be omitted in calls: M(1, 2, 3); // ordinary call of M M(1, 2); // omitting z – equivalent to M(1, 2, 7) M(1); // omitting both y and z – equivalent to M(1, 5, 7) Named and optional arguments C# 4.0 does not permit you to omit arguments between commas as in M(1,,3). This could lead to highly unreadable comma-counting code. Instead any argument can be passed by name. Thus if you want to omit only y from a call of M you can write: M(1, z: 3); // passing z by name or M(x: 1, z: 3); // passing both x and z by name or even M(z: 3, x: 1); // reversing the order of arguments All forms are equivalent, except that arguments are always evaluated in the order they appear, so in the last example the 3 is evaluated before the 1. Optional and named arguments can be used not only with methods but also with indexers and constructors. Overload resolution Named and optional arguments affect overload resolution, but the changes are relatively simple: A signature is applicable if all its parameters are either optional or have exactly one corresponding argument (by name or position) in the call which is convertible to the parameter type. Betterness rules on conversions are only applied for arguments that are explicitly given – omitted optional arguments are ignored for betterness purposes. If two signatures are equally good, one that does not omit optional parameters is preferred. M(string s, int i = 1); M(object o); M(int i, string s = “Hello”); M(int i); M(5); Given these overloads, we can see the working of the rules above. M(string,int) is not applicable because 5 doesn’t convert to string. M(int,string) is applicable because its second parameter is optional, and so, obviously are M(object) and M(int). M(int,string) and M(int) are both better than M(object) because the conversion from 5 to int is better than the conversion from 5 to object. Finally M(int) is better than M(int,string) because no optional arguments are omitted. Thus the method that gets called is M(int). Features for COM interop Dynamic lookup as well as named and optional parameters greatly improve the experience of interoperating with COM APIs such as the Office Automation APIs. In order to remove even more of the speed bumps, a couple of small COM-specific features are also added to C# 4.0. 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 from context, but explicitly has to perform a cast on the returned value to make use of that knowledge. These casts are so common that they constitute a major nuisance. In order to facilitate a smoother experience, you can now choose to import these COM APIs in such a way that variants are instead represented using the type dynamic. In other words, from your point of view, COM signatures now have occurrences of dynamic instead of object in them. This means that you can easily access members directly off a returned object, or you can assign it to a strongly typed local variable without having to cast. To illustrate, you can now say excel.Cells[1, 1].Value = "Hello"; instead of ((Excel.Range)excel.Cells[1, 1]).Value2 = "Hello"; and Excel.Range range = excel.Cells[1, 1]; instead of Excel.Range range = (Excel.Range)excel.Cells[1, 1]; Compiling without PIAs Primary Interop Assemblies are large .NET assemblies generated from COM interfaces to facilitate strongly typed interoperability. They provide great support at design time, where your experience of the interop is as good as if the types where really defined in .NET. However, at runtime these large assemblies can easily bloat your program, and also cause versioning issues because they are distributed independently of your application. The no-PIA feature allows you to continue to use PIAs at design time without having them around at runtime. Instead, the C# compiler will bake the small part of the PIA that a program actually uses directly into its assembly. At runtime the PIA does not have to be loaded. Omitting ref Because of a different programming model, many COM APIs contain a lot of reference parameters. Contrary to refs in C#, these are typically not meant to mutate a passed-in argument for the subsequent benefit of the caller, but are simply another way of passing value parameters. It therefore seems unreasonable that a C# programmer should have to create temporary variables for all such ref parameters and pass these by reference. Instead, specifically for COM methods, the C# compiler will allow you to pass arguments by value to such a method, and will automatically generate temporary variables to hold the passed-in values, subsequently discarding these when the call returns. In this way the caller sees value semantics, and will not experience any side effects, but the called method still gets a reference. Open issues A few COM interface features still are not surfaced in C#. Most notably these include indexed properties and default properties. As mentioned above these will be respected if you access COM dynamically, but statically typed C# code will still not recognize them. There are currently no plans to address these remaining speed bumps in C# 4.0. Variance An aspect of generics that often comes across as surprising is that the following is illegal: IList<string> strings = new List<string>(); IList<object> objects = strings; The second assignment is disallowed because strings does not have the same element type as objects. There is a perfectly good reason for this. If it were allowed you could write: objects[0] = 5; string s = strings[0]; Allowing an int to be inserted into a list of strings and subsequently extracted as a string. This would be a breach of type safety. However, there are certain interfaces where the above cannot occur, notably where there is no way to insert an object into the collection. Such an interface is IEnumerable<T>. If instead you say: IEnumerable<object> objects = strings; There is no way we can put the wrong kind of thing into strings through objects, because objects doesn’t have a method that takes an element in. Variance is about allowing assignments such as this in cases where it is safe. The result is that a lot of situations that were previously surprising now just work. Covariance In .NET 4.0 the IEnumerable<T> interface will be declared in the following way: public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> : IEnumerator { bool MoveNext(); T Current { get; } } The “out” in these declarations signifies that the T can only occur in output position in the interface – the compiler will complain otherwise. In return for this restriction, the interface becomes “covariant” in T, which means that an IEnumerable<A> is considered an IEnumerable<B> if A has a reference conversion to B. As a result, any sequence of strings is also e.g. a sequence of objects. This is useful e.g. in many LINQ methods. Using the declarations above: var result = strings.Union(objects); // succeeds with an IEnumerable<object> This would previously have been disallowed, and you would have had to to some cumbersome wrapping to get the two sequences to have the same element type. Contravariance Type parameters can also have an “in” modifier, restricting them to occur only in input positions. An example is IComparer<T>: public interface IComparer<in T> { public int Compare(T left, T right); } The somewhat baffling result is that an IComparer<object> can in fact be considered an IComparer<string>! It makes sense when you think about it: If a comparer can compare any two objects, it can certainly also compare two strings. This property is referred to as contravariance. A generic type can have both in and out modifiers on its type parameters, as is the case with the Func<…> delegate types: public delegate TResult Func<in TArg, out TResult>(TArg arg); Obviously the argument only ever comes in, and the result only ever comes out. Therefore a Func<object,string> can in fact be used as a Func<string,object>. Limitations Variant type parameters can only be declared on interfaces and delegate types, due to a restriction in the CLR. Variance only applies when there is a reference conversion between the type arguments. For instance, an IEnumerable<int> is not an IEnumerable<object> because the conversion from int to object is a boxing conversion, not a reference conversion. Also please note that the CTP does not contain the new versions of the .NET types mentioned above. In order to experiment with variance you have to declare your own variant interfaces and delegate types. COM Example Here is a larger Office automation example that shows many of the new C# features in action. using System; using System.Diagnostics; using System.Linq; using Excel = Microsoft.Office.Interop.Excel; using Word = Microsoft.Office.Interop.Word; class Program { static void Main(string[] args) { var excel = new Excel.Application(); excel.Visible = true; excel.Workbooks.Add(); // optional arguments omitted excel.Cells[1, 1].Value = "Process Name"; // no casts; Value dynamically excel.Cells[1, 2].Value = "Memory Usage"; // accessed var processes = Process.GetProcesses() .OrderByDescending(p =&gt; p.WorkingSet) .Take(10); int i = 2; foreach (var p in processes) { excel.Cells[i, 1].Value = p.ProcessName; // no casts excel.Cells[i, 2].Value = p.WorkingSet; // no casts i++; } Excel.Range range = excel.Cells[1, 1]; // no casts Excel.Chart chart = excel.ActiveWorkbook.Charts. Add(After: excel.ActiveSheet); // named and optional arguments chart.ChartWizard( Source: range.CurrentRegion, Title: "Memory Usage in " + Environment.MachineName); //named+optional chart.ChartStyle = 45; chart.CopyPicture(Excel.XlPictureAppearance.xlScreen, Excel.XlCopyPictureFormat.xlBitmap, Excel.XlPictureAppearance.xlScreen); var word = new Word.Application(); word.Visible = true; word.Documents.Add(); // optional arguments word.Selection.Paste(); } } The code is much more terse and readable than the C# 3.0 counterpart. Note especially how the Value property is accessed dynamically. This is actually an indexed property, i.e. a property that takes an argument; something which C# does not understand. However the argument is optional. Since the access is dynamic, it goes through the runtime COM binder which knows to substitute the default value and call the indexed property. Thus, dynamic COM allows you to avoid accesses to the puzzling Value2 property of Excel ranges. Relationship with Visual Basic A number of the features introduced to C# 4.0 already exist or will be introduced in some form or other in Visual Basic: · Late binding in VB is similar in many ways to dynamic lookup in C#, and can be expected to make more use of the DLR in the future, leading to further parity with C#. · Named and optional arguments have been part of Visual Basic for a long time, and the C# version of the feature is explicitly engineered with maximal VB interoperability in mind. · NoPIA and variance are both being introduced to VB and C# at the same time. VB in turn is adding a number of features that have hitherto been a mainstay of C#. As a result future versions of C# and VB will have much better feature parity, for the benefit of everyone. Resources All available resources concerning C# 4.0 can be accessed through the C# Dev Center. Specifically, this white paper and other resources can be found at the Code Gallery site. Enjoy! span.fullpost {display:none;}

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  • Reconciling a new BindingList into a master BindingList using LINQ

    - by Neo
    I have a seemingly simple problem whereby I wish to reconcile two lists so that an 'old' master list is updated by a 'new' list containing updated elements. Elements are denoted by a key property. These are my requirements: All elements in either list that have the same key results in an assignment of that element from the 'new' list over the original element in the 'old' list only if any properties have changed. Any elements in the 'new' list that have keys not in the 'old' list will be added to the 'old' list. Any elements in the 'old' list that have keys not in the 'new' list will be removed from the 'old' list. I found an equivalent problem here - http://stackoverflow.com/questions/161432/ - but it hasn't really been answered properly. So, I came up with an algorithm to iterate through the old and new lists and perform the reconciliation as per the above. Before anyone asks why I'm not just replacing the old list object with the new list object in its entirety, it's for presentation purposes - this is a BindingList bound to a grid on a GUI and I need to prevent refresh artifacts such as blinking, scrollbars moving, etc. So the list object must remain the same, only its updated elements changed. Another thing to note is that the objects in the 'new' list, even if the key is the same and all the properties are the same, are completely different instances to the equivalent objects in the 'old' list, so copying references is not an option. Below is what I've come up with so far - it's a generic extension method for a BindingList. I've put comments in to demonstrate what I'm trying to do. public static class BindingListExtension { public static void Reconcile<T>(this BindingList<T> left, BindingList<T> right, string key) { PropertyInfo piKey = typeof(T).GetProperty(key); // Go through each item in the new list in order to find all updated and new elements foreach (T newObj in right) { // First, find an object in the new list that shares its key with an object in the old list T oldObj = left.First(call => piKey.GetValue(call, null).Equals(piKey.GetValue(newObj, null))); if (oldObj != null) { // An object in each list was found with the same key, so now check to see if any properties have changed and // if any have, then assign the object from the new list over the top of the equivalent element in the old list foreach (PropertyInfo pi in typeof(T).GetProperties()) { if (!pi.GetValue(oldObj, null).Equals(pi.GetValue(newObj, null))) { left[left.IndexOf(oldObj)] = newObj; break; } } } else { // The object in the new list is brand new (has a new key), so add it to the old list left.Add(newObj); } } // Now, go through each item in the old list to find all elements with keys no longer in the new list foreach (T oldObj in left) { // Look for an element in the new list with a key matching an element in the old list if (right.First(call => piKey.GetValue(call, null).Equals(piKey.GetValue(oldObj, null))) == null) { // A matching element cannot be found in the new list, so remove the item from the old list left.Remove(oldObj); } } } } It can be called like this: _oldBindingList.Reconcile(newBindingList, "MyKey") However, I'm looking for perhaps a method of doing the same using LINQ type methods such as GroupJoin<, Join<, Select<, SelectMany<, Intersect<, etc. So far, the problem I've had is that each of these LINQ type methods result in brand new intermediary lists (as a return value) and really, I only want to modify the existing list for all the above reasons. If anyone can help with this, would be most appreciated. If not, no worries, the above method (as it were) will suffice for now. Thanks, Jason

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  • A Closer Look at the HiddenInput Attribute in MVC 2

    - by Steve Michelotti
    MVC 2 includes an attribute for model metadata called the HiddenInput attribute. The typical usage of the attribute looks like this (line #3 below): 1: public class PersonViewModel 2: { 3: [HiddenInput(DisplayValue = false)] 4: public int? Id { get; set; } 5: public string FirstName { get; set; } 6: public string LastName { get; set; } 7: } So if you displayed your PersonViewModel with Html.EditorForModel() or Html.EditorFor(m => m.Id), the framework would detect the [HiddenInput] attribute metadata and produce HTML like this: 1: <input id="Id" name="Id" type="hidden" value="21" /> This is pretty straight forward and allows an elegant way to keep the technical key for your model (e.g., a Primary Key from the database) in the HTML so that everything will be wired up correctly when the form is posted to the server and of course not displaying this value visually to the end user. However, when I was giving a recent presentation, a member of the audience asked me (quite reasonably), “When would you ever set DisplayValue equal to true when using a HiddenInput?” To which I responded, “Well, it’s an edge case. There are sometimes when…er…um…people might want to…um…display this value to the user.” It was quickly apparent to me (and I’m sure everyone else in the room) what a terrible answer this was. I realized I needed to have a much better answer here. First off, let’s look at what is produced if we change our view model to use “true” (which is equivalent to use specifying [HiddenInput] since “true” is the default) on line #3: 1: public class PersonViewModel 2: { 3: [HiddenInput(DisplayValue = true)] 4: public int? Id { get; set; } 5: public string FirstName { get; set; } 6: public string LastName { get; set; } 7: } Will produce the following HTML if rendered from Htm.EditorForModel() in your view: 1: <div class="editor-label"> 2: <label for="Id">Id</label> 3: </div> 4: <div class="editor-field"> 5: 21<input id="Id" name="Id" type="hidden" value="21" /> 6: <span class="field-validation-valid" id="Id_validationMessage"></span> 7: </div> The key is line #5. We get the text of “21” (which happened to be my DB Id in this instance) and also a hidden input element (again with “21”). So the question is, why would one want to use this? The best answer I’ve found is contained in this MVC 2 whitepaper: When a view lets users edit the ID of an object and it is necessary to display the value as well as to provide a hidden input element that contains the old ID so that it can be passed back to the controller. Well, that actually makes sense. Yes, it seems like something that would happen *rarely* but, for those instances, it would enable them easily. It’s effectively equivalent to doing this in your view: 1: <%: Html.LabelFor(m => m.Id) %> 2: <%: Model.Id %> 3: <%: Html.HiddenFor(m => m.Id) %> But it’s allowing you to specify it in metadata on your view model (and thereby take advantage of templated helpers like Html.EditorForModel() and Html.EditorFor()) rather than having to explicitly specifying everything in your view.

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  • Creating my first F# program in my new &ldquo;Expert F# Book&rdquo;

    - by MarkPearl
    So I have a brief hour or so that I can dedicate today to reading my F# book. It’s a public holiday and my wife’s birthday and I have a ton of assignments for UNISA that I need to complete – but I just had to try something in F#. So I read chapter 1 – pretty much an introduction to the rest of the book – it looks good so far. Then I get to chapter 2, called “Getting Started with F# and .NET”. Great, there is a code sample on the first page of the chapter. So I open up VS2010 and create a new F# console project and type in the code which was meant to analyze a string for duplicate words… #light let wordCount text = let words = Split [' '] text let wordset = Set.ofList words let nWords = words.Length let nDups = words.Length - wordSet.Count (nWords, nDups) let showWordCount text = let nWords,nDups = wordCount text printfn "--> %d words in text" nWords printfn "--> %d duplicate words" nDups   So… bad start - VS does not like the “Split” method. It gives me an error message “The value constructor ‘Split’ is not defined”. It also doesn’t like wordSet.Count telling me that the “namespace or module ‘wordSet’ is not defined”. ??? So a bit of googling and it turns out that there was a bit of shuffling of libraries between the CTP of F# and the Beta 2 of F#. To have access to the Split function you need to download the F# PowerPack and hen reference it in your code… I download and install the powerpack and then add the reference to FSharp.Core and FSharp.PowerPack in my project. Still no luck! Some more googling and I get the suggestions I got were something like this…#r "FSharp.PowerPack.dll";; #r "FSharp.PowerPack.Compatibility.dll";; So I add the code above to the top of my Program.fs file and still no joy… I now get an error message saying… Error    1    #r directives may only occur in F# script files (extensions .fsx or .fsscript). Either move this code to a script file, add a '-r' compiler option for this reference or delimit the directive with '#if INTERACTIVE'/'#endif'. So what does that mean? If I put the code straight into the F# interactive it works – but I want to be able to use it in a project. The C# equivalent I would think would be the “Using” keyword. The #r doesn’t seem like it should be in the FSharp code. So I try what the compiler suggests by doing the following…#if INTERACTIVE #r "FSharp.PowerPack.dll";; #r "FSharp.PowerPack.Compatibility.dll";; #endif No luck, the Split method is still not recognized. So wait a second, it mentioned something about FSharp.PowerPack.Compatibility.dll – I haven’t added this as a reference to my project so I add it and remove the two lines of #r code. Partial success – the Split method is now recognized and not underlined, but wordSet.Count is still not working. I look at my code again and it was a case error – the original wordset was mistyped comapred to the wordSet. Some case correction and the compiler is no longer complaining. So the code now seems to work… listed below…#light let wordCount text = let words = String.split [' '] text let wordSet = Set.ofList words let nWords = words.Length let nDups = words.Length - wordSet.Count (nWords, nDups) let showWordCount text = let nWords,nDups = wordCount text printfn "--> %d words in text" nWords printfn "--> %d duplicate words" nDups  So recap – if I wanted to use the interactive compiler then I need to put the #r code. In my mind this is the equivalent of me adding the the references to my project. If however I want to use the powerpack in a project – I just need to make sure that the correct references are there. I feel like a noob once again!

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  • Remote Desktop (Vino-Server) connects but display doesn't work?

    - by kmassada
    Ubuntu comes default with vino-server, I can remote into my machine, and connect to it, however, the display inside my remote client, is a mirror of my own desktop. I tried using one monitor, thinking that's what is the issue but still won't work. (vino-server:3608): EggSMClient-CRITICAL **: egg_sm_client_set_mode: assertion `global_client == NULL || global_client_mode == EGG_SM_CLIENT_MODE_DISABLED' failed 25/07/2012 12:23:58 PM Autoprobing TCP port in (all) network interface 25/07/2012 12:23:58 PM Listening IPv6://[::]:5900 25/07/2012 12:23:58 PM Listening IPv4://0.0.0.0:5900 25/07/2012 12:23:58 PM Autoprobing selected port 5900 25/07/2012 12:23:58 PM Advertising security type: 'TLS' (18) 25/07/2012 12:23:58 PM Re-binding socket to listen for VNC connections on TCP port 5900 in (all) interface 25/07/2012 12:23:58 PM Listening IPv6://[::]:5900 25/07/2012 12:23:58 PM Listening IPv4://0.0.0.0:5900 25/07/2012 12:23:58 PM Clearing securityTypes 25/07/2012 12:23:58 PM Advertising security type: 'TLS' (18) 25/07/2012 12:23:58 PM Clearing securityTypes 25/07/2012 12:23:58 PM Advertising security type: 'TLS' (18) 25/07/2012 12:23:58 PM Advertising authentication type: 'No Authentication' (1) 25/07/2012 12:23:58 PM Re-binding socket to listen for VNC connections on TCP port 5900 in (all) interface 25/07/2012 12:23:58 PM Listening IPv6://[::]:5900 25/07/2012 12:23:58 PM Listening IPv4://0.0.0.0:5900 25/07/2012 12:23:58 PM Clearing securityTypes 25/07/2012 12:23:58 PM Clearing authTypes 25/07/2012 12:23:58 PM Advertising security type: 'TLS' (18) 25/07/2012 12:23:58 PM Advertising authentication type: 'VNC Authentication' (2) 25/07/2012 12:23:58 PM Clearing securityTypes 25/07/2012 12:23:58 PM Clearing authTypes 25/07/2012 12:23:58 PM Advertising security type: 'TLS' (18) 25/07/2012 12:23:58 PM Advertising authentication type: 'VNC Authentication' (2) 25/07/2012 12:23:58 PM Advertising security type: 'VNC Authentication' (2) (vino-server:3608): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent. (vino-server:3608): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent. 25/07/2012 12:24:16 PM [IPv4] Got connection from client static-XXXX.bltmmd.fios.verizon.net 25/07/2012 12:24:16 PM other clients: 25/07/2012 12:24:29 PM Client Protocol Version 3.7 25/07/2012 12:24:29 PM Advertising security type 18 25/07/2012 12:24:29 PM Advertising security type 2 25/07/2012 12:24:30 PM Client returned security type 18 25/07/2012 12:24:30 PM Advertising authentication type 2 25/07/2012 12:24:30 PM Client returned authentication type 2 25/07/2012 12:24:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -258 25/07/2012 12:24:37 PM Enabling NewFBSize protocol extension for client static-XXXX.bltmmd.fios.verizon.net 25/07/2012 12:24:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type 1464686185 25/07/2012 12:24:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -259 25/07/2012 12:24:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -257 (vino-server:3608): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent. 25/07/2012 12:24:55 PM Client static-XXXX.bltmmd.fios.verizon.net gone 25/07/2012 12:24:55 PM Statistics: 25/07/2012 12:24:55 PM key events received 0, pointer events 80 25/07/2012 12:24:55 PM framebuffer updates 43, rectangles 152, bytes 292401 25/07/2012 12:24:55 PM tight rectangles 152, bytes 292401 25/07/2012 12:24:55 PM raw bytes equivalent 11621332, compression ratio 39.744502 25/07/2012 12:25:21 PM [IPv4] Got connection from client static-XXXX.bltmmd.fios.verizon.net 25/07/2012 12:25:21 PM other clients: 25/07/2012 12:25:28 PM Client Protocol Version 3.7 25/07/2012 12:25:28 PM Advertising security type 18 25/07/2012 12:25:28 PM Advertising security type 2 25/07/2012 12:25:28 PM Client returned security type 18 25/07/2012 12:25:29 PM Advertising authentication type 2 25/07/2012 12:25:29 PM Client returned authentication type 2 25/07/2012 12:25:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -258 25/07/2012 12:25:37 PM Enabling NewFBSize protocol extension for client static-XXXX.bltmmd.fios.verizon.net 25/07/2012 12:25:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type 1464686185 25/07/2012 12:25:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -259 25/07/2012 12:25:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -257 (vino-server:3608): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent. 25/07/2012 12:25:47 PM Client static-XXXX.bltmmd.fios.verizon.net gone 25/07/2012 12:25:47 PM Statistics: 25/07/2012 12:25:47 PM key events received 0, pointer events 7283 25/07/2012 12:25:47 PM framebuffer updates 27, rectangles 82, bytes 113354 25/07/2012 12:25:47 PM tight rectangles 82, bytes 113354 25/07/2012 12:25:47 PM raw bytes equivalent 5831432, compression ratio 51.444431 couple of things I notice, the following error occurs over and over again. the menu error seems to be caused by ubuntu, similar problems occur http://trac.wxwidgets.org/ticket/14292, (vino-server:3608): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent. the second one also seem to be a display related issue, can't seem to figure out a solution. I really rather try to fix this issue than have to use the other vnc clients most suggest. (vino-server:3608): EggSMClient-CRITICAL **: egg_sm_client_set_mode: assertion `global_client == NULL || global_client_mode == EGG_SM_CLIENT_MODE_DISABLED' failed

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  • Confused about home screen widget size in normal screen and larget screen

    - by kknight
    I am designing a home screen widget. The widget layout file is like below. <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/widget" android:layout_width="240dip" android:layout_height="200dip" android:background="@drawable/base_all" /> I ran this widget on a HTC Hero device, which has a screen of 320 pixels * 480 pixels with mdpi. It ran perfect on HTC Hero. The widget takes 3 cells * 2 cells space, i.e. 240 pixels * 200 pixels. Then I ran this widget on a Nexus One device, which has a screen of 480 pixels * 800 pixels, mdpi. Since Nexus One also is mdpi, so I though 240dip is equivalent to 240 pixels on Nexus One and 200dip is equivalent to 200 pixels on Nexus One, so the widget will not take 3 cells * 2 cells space on Nexus One device. To my surprise, when running on Nexus One device, the widget take exact 3 cells * 2 cells, about 360 pixels * 300 pixels, on Nexus One device. I am confused. The layout xml above specifies 240dip in width and 200dip in height for the widget, but why did it take 360 pixels * 300 pixels on Nexus One Device? What am I missing? Thanks.

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