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  • Unable to assign command output to a variable

    - by Harish Maralihalli
    I am trying to assign the latest file name obtained from the below ls command but getting some error, it would be very nice if someone can answer how can I fix this! fn=`ls -lrt pur_bom_interface_daily*.log | cut -c59-102 | tail -1` or fn=$(ls -lrt pur_bom_interface_daily*.log | cut -c59-102 | tail -1) Error got: ls: 0653-341 The file pur_bom_interface_daily*.log does not exist Note: pur_bom_interface_daily*.log I am using * since there are multiple files starting their name with pur_bom_interface_daily and concatanated with the date on which they have got created.

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  • Subterranean IL: Fault exception handlers

    - by Simon Cooper
    Fault event handlers are one of the two handler types that aren't available in C#. It behaves exactly like a finally, except it is only run if control flow exits the block due to an exception being thrown. As an example, take the following method: .method public static void FaultExample(bool throwException) { .try { ldstr "Entering try block" call void [mscorlib]System.Console::WriteLine(string) ldarg.0 brfalse.s NormalReturn ThrowException: ldstr "Throwing exception" call void [mscorlib]System.Console::WriteLine(string) newobj void [mscorlib]System.Exception::.ctor() throw NormalReturn: ldstr "Leaving try block" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } fault { ldstr "Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } Return: ldstr "Returning from method" call void [mscorlib]System.Console::WriteLine(string) ret } If we pass true to this method the following gets printed: Entering try block Throwing exception Fault handler and the exception gets passed up the call stack. So, the exception gets thrown, the fault handler gets run, and the exception propagates up the stack afterwards in the normal way. If we pass false, we get the following: Entering try block Leaving try block Returning from method Because we are leaving the .try using a leave.s instruction, and not throwing an exception, the fault handler does not get called. Fault handlers and C# So why were these not included in C#? It seems a pretty simple feature; one extra keyword that compiles in exactly the same way, and with the same semantics, as a finally handler. If you think about it, the same behaviour can be replicated using a normal catch block: try { throw new Exception(); } catch { // fault code goes here throw; } The catch block only gets run if an exception is thrown, and the exception gets rethrown and propagates up the call stack afterwards; exactly like a fault block. The only complications that occur is when you want to add a fault handler to a try block with existing catch handlers. Then, you either have to wrap the try in another try: try { try { // ... } catch (DirectoryNotFoundException) { // ... // leave.s as normal... } catch (IOException) { // ... throw; } } catch { // fault logic throw; } or separate out the fault logic into another method and call that from the appropriate handlers: try { // ... } catch (DirectoryNotFoundException ) { // ... } catch (IOException ioe) { // ... HandleFaultLogic(); throw; } catch (Exception e) { HandleFaultLogic(); throw; } To be fair, the number of times that I would have found a fault handler useful is minimal. Still, it's quite annoying knowing such functionality exists, but you're not able to access it from C#. Fortunately, there are some easy workarounds one can use instead. Next time: filter handlers.

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  • ubuntu 12.04 installation problem on windows 7 64bit

    - by zakariya
    06-26 20:57 ERROR TaskList: Extraction failed with code: 2 Traceback (most recent call last): File "\lib\wubi\backends\common\tasklist.py", line 197, in __call__ File "\lib\wubi\backends\win32\backend.py", line 450, in extract_diskimage Exception: Extraction failed with code: 2 06-26 20:57 DEBUG TaskList: # Cancelling tasklist 06-26 20:57 DEBUG TaskList: # Finished tasklist 06-26 20:57 ERROR root: Extraction failed with code: 2 Traceback (most recent call last): File "\lib\wubi\application.py", line 58, in run File "\lib\wubi\application.py", line 132, in select_task File "\lib\wubi\application.py", line 158, in run_installer File "\lib\wubi\backends\common\tasklist.py", line 197, in __call__ File "\lib\wubi\backends\win32\backend.py", line 450, in extract_diskimage Exception: Extraction failed with code: 2

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  • ????????: EXACHK - EXADATA?????? (Exachk???????)

    - by Steve He(???)
    ???????: ?? Exachk ????????;???? Exachk ?? Exadata ???????, ??? Oracle ???????????????????, ?????????, ????, ?? Exadata ???????? ??: 2013?1?17???????3:00 ??: https://oracleaw.webex.com/oracleaw/onstage/g.php?d=592264766&t=a ?????????,???????????: ?? ID: 71587530 UK standard International:+44 1452 562 665 South China Free call: 1080 044 111 82 North China Free call: 1080 074 413 29 Taiwan Free call: 0080 104 4259 Hong Kong Free Call: 8009 661 55

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  • Doctrine Build-All Task fails in NetBeans - Class not found! Fatal Error: call to evictAll()

    - by Prasad
    When I build my model with the symfony doctrine:build --all --and-load command I have made no major changes to the model/schema, this is something new. I also tried sub-commands like build-model, build-tables, but they all hang.. I'm trying this in net beans. Any clue what this is? This command will remove all data in the following "dev" connection(s): - doctrine Are you sure you want to proceed? (y/N) y >> doctrine Dropping "doctrine" database >> doctrine Creating "dev" environment "doctrine" database >> doctrine generating model classes >> file+ C:\Documents and Settings\Gupte...\Temp/doctrine_schema_69845.yml >> tokens D:/projects/cim/lib/model/doctrine/base/BaseAffiliate.class.php >> tokens D:/projects/cim/lib/model/doctrine/base/BaseContact.class.php >> tokens D:/projects/cim/lib/model/doctr...e/BaseContactLocation.class.php >> tokens D:/projects/cim/lib/model/doctr...se/BaseGroupAffiliate.class.php >> tokens D:/projects/cim/lib/model/doctrine/base/BaseGrouping.class.php >> tokens D:/projects/cim/lib/model/doctrine/base/BaseLocation.class.php >> tokens D:/projects/cim/lib/model/doctr.../base/BasePhonenumber.class.php >> tokens D:/projects/cim/lib/model/doctrine/base/BaseTenant.class.php >> tokens D:/projects/cim/lib/model/doctr...base/BasesfGuardGroup.class.php >> tokens D:/projects/cim/lib/model/doctr...fGuardGroupPermission.class.php >> tokens D:/projects/cim/lib/model/doctr...BasesfGuardPermission.class.php >> tokens D:/projects/cim/lib/model/doctr...asesfGuardRememberKey.class.php >> tokens D:/projects/cim/lib/model/doctr.../base/BasesfGuardUser.class.php >> tokens D:/projects/cim/lib/model/doctr.../BasesfGuardUserGroup.class.php >> tokens D:/projects/cim/lib/model/doctr...sfGuardUserPermission.class.php >> autoload Resetting application autoloaders >> file- D:/projects/cim/cache/frontend/.../config/config_autoload.yml.php >> file- D:/projects/cim/cache/backend/dev/config/config_autoload.yml.php >> doctrine generating form classes [?php /** * Contact form base class. * * @method Contact getObject() Returns the current form's model object * * @package ##PROJECT_NAME## * @subpackage form * @author ##AUTHOR_NAME## * @version SVN: $Id: sfDoctrineFormGeneratedTemplate.php 24171 2009-11-19 16:37:50Z Kris.Wallsmith $ */ abstract class BaseContactForm extends BaseFormDoctrine { public function setup() { $this->setWidgets(array( 'id' Fatal error: Call to a member function evictAll() on a non-object in D:\projects\cim\lib\vendor\symfony\lib\plugins\sfDoctrinePlugin\lib\vendor\doctrine\Doctrine\Connection.php on line 1239 Call Stack: 0.9552 322760 1. {main}() D:\projects\cim\symfony:0 0.9594 587208 2. include('D:\projects\cim\lib\vendor\symfony\lib\command\cli.php') D:\projects\cim\symfony:14 11.9775 17118936 3. sfDatabaseManager->shutdown() D:\projects\cim\lib\vendor\symfony\lib\database\sfDatabaseManager.class.php:0 11.9775 17118936 4. sfDoctrineDatabase->shutdown() D:\projects\cim\lib\vendor\symfony\lib\database\sfDatabaseManager.class.php:134 11.9775 17118936 5. Doctrine_Manager->closeConnection() D:\projects\cim\lib\vendor\symfony\lib\plugins\sfDoctrinePlugin\lib\database\sfDoctrineDatabase.class.php:165 11.9775 17118936 6. Doctrine_Connection->close() D:\projects\cim\lib\vendor\symfony\lib\plugins\sfDoctrinePlugin\lib\vendor\doctrine\Doctrine\Manager.php:579 11.9776 17120160 7. Doctrine_Connection->clear() D:\projects\cim\lib\vendor\symfony\lib\plugins\sfDoctrinePlugin\lib\vendor\doctrine\Doctrine\Connection.php:1268 Couldn't find class Similar thing is mentioned here: http://osdir.com/ml/symfony-users/2010-01/msg00642.html

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  • Call an member function implementing the {{#linkTo ...}} helper from javascript code

    - by gonvaled
    I am trying to replace this navigation menu: <nav> {{#linkTo "nodes" }}<i class="icon-fixed-width icon-cloud icon-2x"></i>&nbsp;&nbsp;{{t generic.nodes}} {{grayOut "(temporal)"}}{{/linkTo}} {{#linkTo "services" }}<i class="icon-fixed-width icon-phone icon-2x"></i>&nbsp;&nbsp;{{t generic.services}}{{/linkTo}} {{#linkTo "agents" }}<i class="icon-fixed-width icon-headphones icon-2x"></i>&nbsp;&nbsp;{{t generic.agents}}{{/linkTo}} {{#linkTo "extensions" }}<i class="icon-fixed-width icon-random icon-2x"></i>&nbsp;&nbsp;{{t generic.extensions}}{{/linkTo}} {{#linkTo "voiceMenus" }}<i class="icon-fixed-width icon-sitemap icon-2x"></i>&nbsp;&nbsp;{{t generic.voicemenus}}{{/linkTo}} {{#linkTo "queues" }}<i class="icon-fixed-width icon-tasks icon-2x"></i>&nbsp;&nbsp;{{t generic.queues}}{{/linkTo}} {{#linkTo "contacts" }}<i class="icon-fixed-width icon-user icon-2x"></i>&nbsp;&nbsp;{{t generic.contacts}}{{/linkTo}} {{#linkTo "accounts" }}<i class="icon-fixed-width icon-building icon-2x"></i>&nbsp;&nbsp;{{t generic.accounts}}{{/linkTo}} {{#linkTo "locators" }}<i class="icon-fixed-width icon-phone-sign icon-2x"></i>&nbsp;&nbsp;{{t generic.locators}}{{/linkTo}} {{#linkTo "phonelocations" }}<i class="icon-fixed-width icon-globe icon-2x"></i>&nbsp;&nbsp;{{t generic.phonelocations}}{{/linkTo}} {{#linkTo "billing" }}<i class="icon-fixed-width icon-euro icon-2x"></i>&nbsp;&nbsp;{{t generic.billing}}{{/linkTo}} {{#linkTo "profile" }}<i class="icon-fixed-width icon-cogs icon-2x"></i>&nbsp;&nbsp;{{t generic.profile}}{{/linkTo}} {{#linkTo "audio" }}<i class="icon-fixed-width icon-music icon-2x"></i>&nbsp;&nbsp;{{t generic.audio}}{{/linkTo}} {{#linkTo "editor" }}<i class="icon-fixed-width icon-puzzle-piece icon-2x"></i>&nbsp;&nbsp;{{t generic.node_editor}}{{/linkTo}} </nav> With a more dynamic version. What I am trying to do is to reproduce the html inside Ember.View.render, but I would like to reuse as much Ember functionality as possible. Specifically, I would like to reuse the {{#linkTo ...}} helper, with two goals: Reuse existing html rendering implemented in the {{#linkTo ...}} helper Get the same routing support that using the {{#linkTo ...}} in a template provides. How can I call this helper from within javascript code? This is my first (incomplete) attempt. The template: {{view SettingsApp.NavigationView}} And the view: var trans = Ember.I18n.t; var MAIN_MENU = [ { 'linkTo' : 'nodes', 'i-class' : 'icon-cloud', 'txt' : trans('generic.nodes') }, { 'linkTo' : 'services', 'i-class' : 'icon-phone', 'txt' : trans('generic.services') }, ]; function getNavIcon (data) { var linkTo = data.linkTo, i_class = data['i-class'], txt = data.txt; var html = '<i class="icon-fixed-width icon-2x ' + i_class + '"></i>&nbsp;&nbsp;' + txt; return html; } SettingsApp.NavigationView = Ember.View.extend({ menu : MAIN_MENU, render: function(buffer) { for (var i=0, l=this.menu.length; i<l; i++) { var data = this.menu[i]; // TODO: call the ember function implementing the {{#linkTo ...}} helper buffer.push(getNavIcon(data)); } return buffer; } });

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  • How can I hit my database with an AJAX call using javascript?

    - by tmedge
    I am pretty new at this stuff, so bear with me. I am using ASP.NET MVC. I have created an overlay to cover the page when someone clicks a button corresponding to a certain database entry. Because of this, ALL of my code for this functionality is in a .js file contained within my project. What I need to do is pull the info corresponding to my entry from the database itself using an AJAX call, and place that into my textboxes. Then, after the end-user has made the desired changes, I need to update that entry's values to match the input. I've been surfing the web for a while, and have failed to find an example that fits my needs effectively. Here is my code in my javascript file thus far: function editOverlay(picId) { //pull up an overlay $('body').append('<div class="overlay" />'); var $overlayClass = $('.overlay'); $overlayClass.append('<div class="dataModal" />'); var $data = $('.dataModal'); overlaySetup($overlayClass, $data); //set up form $data.append('<h1>Edit Picture</h1><br /><br />'); $data.append('Picture name: &nbsp;'); $data.append('<input class="picName" /> <br /><br /><br />'); $data.append('Relative url: &nbsp;'); $data.append('<input class="picRelURL" /> <br /><br /><br />'); $data.append('Description: &nbsp;'); $data.append('<textarea class="picDescription" /> <br /><br /><br />'); var $nameBox = $('.picName'); var $urlBox = $('.picRelURL'); var $descBox = $('.picDescription'); var pic = null; //this is where I need to pull the actual object from the db //var imgList = for (var temp in imgList) { if (temp.Id == picId) { pic= temp; } } /* $nameBox.attr('value', pic.Name); $urlBox.attr('value', pic.RelativeURL); $descBox.attr('value', pic.Description); */ //close buttons $data.append('<input type="button" value="Save Changes" class="saveButton" />'); $data.append('<input type="button" value="Cancel" class="cancelButton" />'); $('.saveButton').click(function() { /* pic.Name = $nameBox.attr('value'); pic.RelativeURL = $urlBox.attr('value'); pic.Description = $descBox.attr('value'); */ //make a call to my Save() method in my repository CloseOverlay(); }); $('.cancelButton').click(function() { CloseOverlay(); }); } The stuff I have commented out is what I need to accomplish and/or is not available until prior issues are resolved. Any and all advice is appreciated! Remember, I am VERY new to this stuff (two weeks, to be exact) and will probably need highly explicit instructions. BTW: overlaySetup() and CloseOverlay() are functions I have living someplace else. Thanks!

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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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  • Why does this call to jQuery's $.ajax() fire an empty request in Chrome and Firefox?

    - by Martin Wiboe
    Hello, I am trying to call a WCF RESTful service from jQuery. I am using JSON to encode both request and response. The following code functions correctly in IE8: url = 'http://ipv4.fiddler:5683/WeatherWCF/NewBinding/MyService/GetValueFloat'; $.ajax({ url: url, data: '{"alias": "Udetemperatur"}', type: "POST", contentType: "application/json; charset=utf-8", dataType: "text", // not "json" we'll parse success: function(res) { alert('Received response: ' + res); } }); However, in both Firefox and Chrome, res contains an empty string. After using Fiddler to monitor the request, it appears that jQuery sends an empty request to the server as shown in this screen dump: http://imgur.com/EJgwS.png This is the successful request: http://imgur.com/S77BA.png What am I doing wrong? Kind regards, Martin

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  • How do i make a "system call to tar files(along with exclude tag)" to work in Perl

    - by superstar
    This is the system call, i am making right now in perl to tar the files system("${tarexe} -pcvf $tarname $includepath") which works fine. $tarexe -> location of my tar.exe file $tarname -> myMock.tar $includepath -> ./input/myMockPacketName ./input/myPacket/my2/*.wav ./input/myPacket/my3 ./input/myPacket/in.html Now i want to exclude some files using exclude tag, which doesnot exclude the files system("${tarexe} -pcvf $tarname $includepath --exclude $excludepath") $excludepath -> ./input/myMockPacketName/my3 The same stament ${tarexe} -pcvf $tarname $includepath --exclude $excludepath works fine when i run it in the command line.

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  • How to Force a Method Call on a Property or Method of an Object in PHP?

    - by Noah Goodrich
    In my View (using Zend_View so the the view is an object), I make calls to object properties and methods to populate the template like so: <?= $this->user->name ?> // Outputs John Doe <br/> <?= $this->user->getCompany()->name ?> // Outputs Acme <br/> <?= $this->method() ?> // Outputs foobar If I make it so that all property requests (like for 'user') go through __get() is there any way that I can catch the subsequent calls so that I can force a method call on the final outputted value? For example so that I could do automatic escaping of output. As I see it right now, I either have to escape the input as it goes into the database or use compiled templates like Smarty does, or switch to assigning every variable to the View object so that it has direct control to force escaping before outputting the data.

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  • Can you handle both json and html datatypes in the same ajax call?

    - by Prabhu
    Is there anyway I can handle both json and html return types when posting jquery ajax: For example, this ajax call expects html back $.ajax({ type: "POST", url: url data: data, dataType: "html", success: function (response) { var $html = "<li class='list-item'>" + response + "</li>"; $('#a').prepend($html); }, error: function (xhr, status, error) { alert(xhr.statusText); } }); but I wanted to modify it so that I can return a json object if there is a model error. so I can do something like this: success: function (response) { if (response.Error){ alert(response.Message); } else { var $html = "<li class='list-item'>" + response + "</li>"; $('#a').prepend($html); } Is this possible?

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  • Why can't I call methods within a class that explicitly implements an interface?

    - by tyrone302
    Here's the story. I created and interface, IVehicle. I explicitly implemented the interface in my class, Vehicle.cs. Here is my interface: Interface IVehicle { int getWheel(); } here is my class: class Vehicle: IVehicle { public int IVehicle.getWheel() { return wheel; } public void printWheel() { Console.WriteLine(getWheel()); } } Notice that "getWheel()" is explicitly implemented. Now, when I try to call that method within my Vehicle class, I receive an error indicating that getWheel() does not exist in the current context. Can someone help me understand what I am doing wrong?

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  • Paypal adaptive payment API call with C# .NET? Preferably with WebServices

    - by Phil
    Okay I might be entirely off track now but here goes: Our "webshop" offers two functions, buying a specific product and selling it back to us. Back-end handles if the user can sell or not. I've decided to use Paypal's adaptive payments for this one as it seems the way to go doing these kinds of transactions. I've never implemented any kind of shop so I'm totally green with this one. I only recently learned ASP.NET and have mainly developed games before moving to this kind of development. HTTP is still some level of magic to me hehe.. I might be confused but I think paypal offers a webservice with their adaptive payment API. My humble request: A nice soul who wants to share an example of implementing an adaptive payment API call with C# .NET. If they don't offer it as a webservice I'll probably find it as a custom .dll or something. Any tips and examples are highly appreciated! Thanks for reading

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  • It is possible to call a servlet from a Java class?

    - by Renan Mozone
    I'm using IBM WebSphere as my servlet container. My application has several servlets and Java classes. My intent is to call one of those servlets directly from a Java class. Doing some research I figured out that is possible to use the RequestDispatcher interface to achieve this. But it is necessary to pass the objects ServletRequest and ServletResponse as arguments to the method forward(). There is some way to bypass this safely and "nicely"? By "nicely" I meant to say preserving good programming and design patterns.

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  • How do I make a PHP call whenever a form element is clicked?

    - by thinkswan
    I have a jQuery colorbox opened over top of my webpage (with a <select> drop down list) and I'd like to make an AJAX call every time a new <option> is selected from the drop down. I have the following code, but it's not picking up the select event. $('#cboxLoadedContent select[name=parent]').live('select', function() { $.get("edit.php", { fn: 'getFormatLevel', parent: $('select[name=parent]').val() }, function(data) { alert("Data Loaded: " + data); }); }); Any ideas why this isn't even recognizing my selector?

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  • In Android: How to Call Function of Activity from a Service?

    - by nex
    Hi folks, I have an Activity (A) and a Service (S) which gets started by A like this: Intent i = new Intent(); i.putExtra("updateInterval", 10); i.setClassName("com.blah", "com.blah.S"); startService(i); A have a function like this one in A: public void someInfoArrived(Info i){...} Now I want to call A.someInfoArrived(i) from within S. Intent.putExtra has no version where I could pass an Object reference etc ... Please help! PS: The other way around (A polling S for new info) is NOT what I need. I found enough info about how to do that.

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  • What is this obscure error in Google Analytics tracking code on a _trackEvent() call?

    - by Laizer
    I am calling the Google Analytics _trackEvent() function on a web page, and get back an error from the obfuscated Google code. In Firebug, it comes back "q is undefined". In Safari developer console: "TypeError: Result of expression 'q' [undefined] is not an object." As a test, I have reduced the page to only this call, and still get the error back. Besides the necessary elements and the standard Google tracking code, my page is: <script> pageTracker._trackEvent('Survey', 'Checkout - Survey', 'Rating', 3); </script> Results is that error. What's going on here?

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  • Reasons why one should not call the garbage collector directly.

    - by Shimrod
    Hi everyone, I'm currently writing a paper for my company, about how to avoid calling the garbage collector directly from the code (when playing with COM objects for instance). I know this is a bad practice, and should be only considered in very rare cases, but I can't seem to find a way to tell why it should be avoided. And I don't want to rely on the "The G.C. is smarter than you" principle (even if it is the truth :-) ) So can you tell me some clues about why you think one should avoid to call the garbage collector directly ? (performance impact?) Or maybe if you have links about this particular topic, they would be very helpful. Thanks in advance !

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  • How to call a wpf singleton service within a wpf singleton service without hanging?

    - by Michael Hedgpeth
    I have two services, one that calls another. Both are marked as singletons as follows: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)] public class Service : IService And I set these up with a ServiceHost as follows: ServiceHost serviceHost = new ServiceHost(singletonElement); serviceHost.Open(); When the parent service tries to call the child service on the same machine, the parent service hangs, waiting for the child service. I'm already considering moving away from the singleton model, but is there anything wrong with my approach? Is there an explanation for this behavior and a way out of it?

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  • How to call method written in C# class library from Silver light application(xaml.cs file) ?

    - by Shyju
    Can a xaml.cs file call the method in a c# class library ? I am trying to add a Silver light control to my Existing ASP.NET project where i used to add reference to my BL Project and acces methods of BL from My UI pages of ASP.NET Web application.Now i have added one Silver light project to my solution.How can i use the already existing BL method which is in a C# class library ? When tried to add reference, it is saying that "You can only add project reference to other silver light projects in the solution". Should i give up ? Is there any way to get rid of this ?

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  • How to call a WCF singleton service within a WCF singleton service without hanging?

    - by Michael Hedgpeth
    I have two services, one that calls another. Both are marked as singletons as follows: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)] public class Service : IService And I set these up with a ServiceHost as follows: ServiceHost serviceHost = new ServiceHost(singletonElement); serviceHost.Open(); When the parent service tries to call the child service on the same machine, the parent service hangs, waiting for the child service. I'm already considering moving away from the singleton model, but is there anything wrong with my approach? Is there an explanation for this behavior and a way out of it?

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  • How to call webservice using same credentials as Sharepoint?

    - by Saab
    Is it possible to do a webservice call from within an Excel sheet that has been downloaded from a sharepoint server, using the same credentials as the ones that are used for accessing the Sharepoint server? We're currently developing an Excel solution, which does webservice request from within the Excel sheet. This works fine, but the user has to log in at least twice : one for downloading/opening the Excel sheet from Sharepoint, and one to be able to execute the webservice using the right credentials. The Sharepoint server and the client machine are not in the same Active Directory domain. So "System.Security.Principal.WindowsIdentity.GetCurrent()" is not an option, since this will return a user that doesn't exist on the server.

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  • Powershell 2.0 error handling - Command line call vs. ISE

    - by Gromix
    Hi, In the context of deployment scripts, I would like to capture any error than happens and stop immediately. I have notice some significant differences between the following calls: powershell.exe -File Script.ps1 powershell.exe -Command "& '.\Script.ps1'" powershell.exe .\Script.ps1 For example, the -File call will handle errors in the exact same way as the ISE. The other two seem to ignore the $ErrorActionPreference variable, and do not seem to catch Write-Error in try/catch blocks. Could someone help me understand the implications of each one, and why they are behaving differently? Thanks, Romain

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