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  • Working with Tile Notifications in Windows 8 Store Apps – Part I

    - by dwahlin
    One of the features that really makes Windows 8 apps stand out from others is the tile functionality on the start screen. While icons allow a user to start an application, tiles provide a more engaging way to engage the user and draw them into an application. Examples of “live” tiles on part of my current start screen are shown next: I’ll admit that if you get enough of these tiles going the start screen can actually be a bit distracting. Fortunately, a user can easily disable a live tile by right-clicking on it or pressing and holding a tile on a touch device and then selecting Turn live tile off from the AppBar: The can also make a wide tile smaller (into a square tile) or make a square tile bigger assuming the application supports both squares and rectangles. In this post I’ll walk through how to add tile notification functionality into an application. Both XAML/C# and HTML/JavaScript apps support live tiles and I’ll show the code for both options.   Understanding Tile Templates The first thing you need to know if you want to add custom tile functionality (live tiles) into your application is that there is a collection of tile templates available out-of-the-box. Each tile template has XML associated with it that you need to load, update with your custom data, and then feed into a tile update manager. By doing that you can control what shows in your app’s tile on the Windows 8 start screen. So how do you learn more about the different tile templates and their respective XML? Fortunately, Microsoft has a nice documentation page in the Windows 8 Store SDK. Visit http://msdn.microsoft.com/en-us/library/windows/apps/hh761491.aspx to see a complete list of square and wide/rectangular tile templates that you can use. Looking through the templates you’ll It has the following XML template associated with it:  <tile> <visual> <binding template="TileSquareBlock"> <text id="1">Text Field 1</text> <text id="2">Text Field 2</text> </binding> </visual> </tile> An example of a wide/rectangular tile template is shown next:    <tile> <visual> <binding template="TileWideImageAndText01"> <image id="1" src="image1.png" alt="alt text"/> <text id="1">Text Field 1</text> </binding> </visual> </tile>   To use these tile templates (or others you find interesting), update their content, and get them to show for your app’s tile on the Windows 8 start screen you’ll need to perform the following steps: Define the tile template to use in your app Load the tile template’s XML into memory Modify the children of the <binding> tag Feed the modified tile XML into a new TileNotification instance Feed the TileNotification instance into the Update() method of the TileUpdateManager In the remainder of the post I’ll walk through each of the steps listed above to provide wide and square tile notifications for an application. The wide tile that’s shown will show an image and text while the square tile will only show text. If you’re going to provide custom tile notifications it’s recommended that you provide wide and square tiles since users can switch between the two of them directly on the start screen. Note: When working with tile notifications it’s possible to manipulate and update a tile’s XML template without having to know XML parsing techniques. This can be accomplished using some C# notification extension classes that are available. In this post I’m going to focus on working with tile notifications using an XML parser so that the focus is on the steps required to add notifications to the Windows 8 start screen rather than on external extension classes. You can access the extension classes in the Windows 8 samples gallery if you’re interested.   Steps to Create Custom App Tile Notifications   Step 1: Define the tile template to use in your app Although you can cut-and-paste a tile template’s XML directly into your C# or HTML/JavaScript Windows store app and then parse it using an XML parser, it’s easier to use the built-in TileTemplateType enumeration from the Windows.UI.Notifications namespace. It provides direct access to the XML for the various templates so once you locate a template you like in the documentation (mentioned above), simplify reference it:HTML/JavaScript var notifications = Windows.UI.Notifications; var template = notifications.TileTemplateType.tileWideImageAndText01; .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   XAML/C# var template = TileTemplateType.TileWideImageAndText01;   Step 2: Load the tile template’s XML into memory Once the target template’s XML is identified, load it into memory using the TileUpdateManager’s GetTemplateContent() method. This method parses the template XML and returns an XmlDocument object:   HTML/JavaScript   var tileXml = notifications.TileUpdateManager.getTemplateContent(template); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   XAML/C#  var tileXml = TileUpdateManager.GetTemplateContent(template);   Step 3: Modify the children of the <binding> tag Once the XML for a given template is loaded into memory you need to locate the appropriate <image> and/or <text> elements in the XML and update them with your app data. This can be done using standard XML DOM manipulation techniques. The example code below locates the image folder and loads the path to an image file located in the project into it’s inner text. The code also creates a square tile that consists of text, updates it’s <text> element, and then imports and appends it into the wide tile’s XML.   HTML/JavaScript var image = tileXml.selectSingleNode('//image[@id="1"]'); image.setAttribute('src', 'ms-appx:///images/' + imageFile); image.setAttribute('alt', 'Live Tile'); var squareTemplate = notifications.TileTemplateType.tileSquareText04; var squareTileXml = notifications.TileUpdateManager.getTemplateContent(squareTemplate); var squareTileTextAttributes = squareTileXml.selectSingleNode('//text[@id="1"]'); squareTileTextAttributes.appendChild(squareTileXml.createTextNode(content)); var node = tileXml.importNode(squareTileXml.selectSingleNode('//binding'), true); tileXml.selectSingleNode('//visual').appendChild(node); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   XAML/C#var tileXml = TileUpdateManager.GetTemplateContent(template); var text = tileXml.SelectSingleNode("//text[@id='1']"); text.AppendChild(tileXml.CreateTextNode(content)); var image = (XmlElement)tileXml.SelectSingleNode("//image[@id='1']"); image.SetAttribute("src", "ms-appx:///Assets/" + imageFile); image.SetAttribute("alt", "Live Tile"); Debug.WriteLine(image.GetXml()); var squareTemplate = TileTemplateType.TileSquareText04; var squareTileXml = TileUpdateManager.GetTemplateContent(squareTemplate); var squareTileTextAttributes = squareTileXml.SelectSingleNode("//text[@id='1']"); squareTileTextAttributes.AppendChild(squareTileXml.CreateTextNode(content)); var node = tileXml.ImportNode(squareTileXml.SelectSingleNode("//binding"), true); tileXml.SelectSingleNode("//visual").AppendChild(node);  Step 4: Feed the modified tile XML into a new TileNotification instance Now that the XML data has been updated with the desired text and images, it’s time to load the XmlDocument object into a new TileNotification instance:   HTML/JavaScript var tileNotification = new notifications.TileNotification(tileXml); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   XAML/C#var tileNotification = new TileNotification(tileXml);  Step 5: Feed the TileNotification instance into the Update() method of the TileUpdateManager Once the TileNotification instance has been created and the XmlDocument has been passed to its constructor, it needs to be passed to the Update() method of a TileUpdator in order to be shown on the Windows 8 start screen:   HTML/JavaScript notifications.TileUpdateManager.createTileUpdaterForApplication().update(tileNotification); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   XAML/C#TileUpdateManager.CreateTileUpdaterForApplication().Update(tileNotification);    Once the tile notification is updated it’ll show up on the start screen. An example of the wide and square tiles created with the included demo code are shown next:     Download the HTML/JavaScript and XAML/C# sample application here. In the next post in this series I’ll walk through how to queue multiple tiles and clear a queue.

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  • Connecting SceneBuilder edited FXML to Java code

    - by daniel
    Recently I had to answer several questions regarding how to connect an UI built with the JavaFX SceneBuilder 1.0 Developer Preview to Java Code. So I figured out that a short overview might be helpful. But first, let me state the obvious. What is FXML? To make it short, FXML is an XML based declaration format for JavaFX. JavaFX provides an FXML loader which will parse FXML files and from that construct a graph of Java object. It may sound complex when stated like that but it is actually quite simple. Here is an example of FXML file, which instantiate a StackPane and puts a Button inside it: -- <?xml version="1.0" encoding="UTF-8"?> <?import java.lang.*?> <?import java.util.*?> <?import javafx.scene.control.*?> <?import javafx.scene.layout.*?> <?import javafx.scene.paint.*?> <StackPane prefHeight="150.0" prefWidth="200.0" xmlns:fx="http://javafx.com/fxml"> <children> <Button mnemonicParsing="false" text="Button" /> </children> </StackPane> ... and here is the code I would have had to write if I had chosen to do the same thing programatically: import javafx.scene.control.*; import javafx.scene.layout.*; ... final Button button = new Button("Button"); button.setMnemonicParsing(false); final StackPane stackPane = new StackPane(); stackPane.setPrefWidth(200.0); stackPane.setPrefHeight(150.0); stacPane.getChildren().add(button); As you can see - FXML is rather simple to understand - as it is quite close to the JavaFX API. So OK FXML is simple, but why would I use it?Well, there are several answers to that - but my own favorite is: because you can make it with SceneBuilder. What is SceneBuilder? In short SceneBuilder is a layout tool that will let you graphically build JavaFX user interfaces by dragging and dropping JavaFX components from a library, and save it as an FXML file. SceneBuilder can also be used to load and modify JavaFX scenegraphs declared in FXML. Here is how I made the small FXML file above: Start the JavaFX SceneBuilder 1.0 Developer Preview In the Library on the left hand side, click on 'StackPane' and drag it on the content view (the white rectangle) In the Library, select a Button and drag it onto the StackPane on the content view. In the Hierarchy Panel on the left hand side - select the StackPane component, then invoke 'Edit > Trim To Selected' from the menubar That's it - you can now save, and you will obtain the small FXML file shown above. Of course this is only a trivial sample, made for the sake of the example - and SceneBuilder will let you create much more complex UIs. So, I have now an FXML file. But what do I do with it? How do I include it in my program? How do I write my main class? Loading an FXML file with JavaFX Well, that's the easy part - because the piece of code you need to write never changes. You can download and look at the SceneBuilder samples if you need to get convinced, but here is the short version: Create a Java class (let's call it 'Main.java') which extends javafx.application.Application In the same directory copy/save the FXML file you just created using SceneBuilder. Let's name it "simple.fxml" Now here is the Java code for the Main class, which simply loads the FXML file and puts it as root in a stage's scene. /* * Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved. */ package simple; import java.util.logging.Level; import java.util.logging.Logger; import javafx.application.Application; import javafx.fxml.FXMLLoader; import javafx.scene.Scene; import javafx.scene.layout.StackPane; import javafx.stage.Stage; public class Main extends Application { /** * @param args the command line arguments */ public static void main(String[] args) { Application.launch(Main.class, (java.lang.String[])null); } @Override public void start(Stage primaryStage) { try { StackPane page = (StackPane) FXMLLoader.load(Main.class.getResource("simple.fxml")); Scene scene = new Scene(page); primaryStage.setScene(scene); primaryStage.setTitle("FXML is Simple"); primaryStage.show(); } catch (Exception ex) { Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex); } } } Great! Now I only have to use my favorite IDE to compile the class and run it. But... wait... what does it do? Well nothing. It just displays a button in the middle of a window. There's no logic attached to it. So how do we do that? How can I connect this button to my application logic? Here is how: Connection to code First let's define our application logic. Since this post is only intended to give a very brief overview - let's keep things simple. Let's say that the only thing I want to do is print a message on System.out when the user clicks on my button. To do that, I'll need to register an action handler with my button. And to do that, I'll need to somehow get a handle on my button. I'll need some kind of controller logic that will get my button and add my action handler to it. So how do I get a handle to my button and pass it to my controller? Once again - this is easy: I just need to write a controller class for my FXML. With each FXML file, it is possible to associate a controller class defined for that FXML. That controller class will make the link between the UI (the objects defined in the FXML) and the application logic. To each object defined in FXML we can associate an fx:id. The value of the id must be unique within the scope of the FXML, and is the name of an instance variable inside the controller class, in which the object will be injected. Since I want to have access to my button, I will need to add an fx:id to my button in FXML, and declare an @FXML variable in my controller class with the same name. In other words - I will need to add fx:id="myButton" to my button in FXML: -- <Button fx:id="myButton" mnemonicParsing="false" text="Button" /> and declare @FXML private Button myButton in my controller class @FXML private Button myButton; // value will be injected by the FXMLLoader Let's see how to do this. Add an fx:id to the Button object Load "simple.fxml" in SceneBuilder - if not already done In the hierarchy panel (bottom left), or directly on the content view, select the Button object. Open the Properties sections of the inspector (right panel) for the button object At the top of the section, you will see a text field labelled fx:id. Enter myButton in that field and validate. Associate a controller class with the FXML file Still in SceneBuilder, select the top root object (in our case, that's the StackPane), and open the Code section of the inspector (right hand side) At the top of the section you should see a text field labelled Controller Class. In the field, type simple.SimpleController. This is the name of the class we're going to create manually. If you save at this point, the FXML will look like this: -- <?xml version="1.0" encoding="UTF-8"?> <?import java.lang.*?> <?import java.util.*?> <?import javafx.scene.control.*?> <?import javafx.scene.layout.*?> <?import javafx.scene.paint.*?> <StackPane prefHeight="150.0" prefWidth="200.0" xmlns:fx="http://javafx.com/fxml" fx:controller="simple.SimpleController"> <children> <Button fx:id="myButton" mnemonicParsing="false" text="Button" /> </children> </StackPane> As you can see, the name of the controller class has been added to the root object: fx:controller="simple.SimpleController" Coding the controller class In your favorite IDE, create an empty SimpleController.java class. Now what does a controller class looks like? What should we put inside? Well - SceneBuilder will help you there: it will show you an example of controller skeleton tailored for your FXML. In the menu bar, invoke View > Show Sample Controller Skeleton. A popup appears, displaying a suggestion for the controller skeleton: copy the code displayed there, and paste it into your SimpleController.java: /** * Sample Skeleton for "simple.fxml" Controller Class * Use copy/paste to copy paste this code into your favorite IDE **/ package simple; import java.net.URL; import java.util.ResourceBundle; import javafx.fxml.FXML; import javafx.fxml.Initializable; import javafx.scene.control.Button; public class SimpleController implements Initializable { @FXML // fx:id="myButton" private Button myButton; // Value injected by FXMLLoader @Override // This method is called by the FXMLLoader when initialization is complete public void initialize(URL fxmlFileLocation, ResourceBundle resources) { assert myButton != null : "fx:id=\"myButton\" was not injected: check your FXML file 'simple.fxml'."; // initialize your logic here: all @FXML variables will have been injected } } Note that the code displayed by SceneBuilder is there only for educational purpose: SceneBuilder does not create and does not modify Java files. This is simply a hint of what you can use, given the fx:id present in your FXML file. You are free to copy all or part of the displayed code and paste it into your own Java class. Now at this point, there only remains to add our logic to the controller class. Quite easy: in the initialize method, I will register an action handler with my button: () { @Override public void handle(ActionEvent event) { System.out.println("That was easy, wasn't it?"); } }); ... -- ... // initialize your logic here: all @FXML variables will have been injected myButton.setOnAction(new EventHandler<ActionEvent>() { @Override public void handle(ActionEvent event) { System.out.println("That was easy, wasn't it?"); } }); ... That's it - if you now compile everything in your IDE, and run your application, clicking on the button should print a message on the console! Summary What happens is that in Main.java, the FXMLLoader will load simple.fxml from the jar/classpath, as specified by 'FXMLLoader.load(Main.class.getResource("simple.fxml"))'. When loading simple.fxml, the loader will find the name of the controller class, as specified by 'fx:controller="simple.SimpleController"' in the FXML. Upon finding the name of the controller class, the loader will create an instance of that class, in which it will try to inject all the objects that have an fx:id in the FXML. Thus, after having created '<Button fx:id="myButton" ... />', the FXMLLoader will inject the button instance into the '@FXML private Button myButton;' instance variable found on the controller instance. This is because The instance variable has an @FXML annotation, The name of the variable exactly matches the value of the fx:id Finally, when the whole FXML has been loaded, the FXMLLoader will call the controller's initialize method, and our code that registers an action handler with the button will be executed. For a complete example, take a look at the HelloWorld SceneBuilder sample. Also make sure to follow the SceneBuilder Get Started guide, which will guide you through a much more complete example. Of course, there are more elegant ways to set up an Event Handler using FXML and SceneBuilder. There are also many different ways to work with the FXMLLoader. But since it's starting to be very late here, I think it will have to wait for another post. I hope you have enjoyed the tour! --daniel

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  • C#/.NET Little Wonders: Interlocked CompareExchange()

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Two posts ago, I discussed the Interlocked Add(), Increment(), and Decrement() methods (here) for adding and subtracting values in a thread-safe, lightweight manner.  Then, last post I talked about the Interlocked Read() and Exchange() methods (here) for safely and efficiently reading and setting 32 or 64 bit values (or references).  This week, we’ll round out the discussion by talking about the Interlocked CompareExchange() method and how it can be put to use to exchange a value if the current value is what you expected it to be. Dirty reads can lead to bad results Many of the uses of Interlocked that we’ve explored so far have centered around either reading, setting, or adding values.  But what happens if you want to do something more complex such as setting a value based on the previous value in some manner? Perhaps you were creating an application that reads a current balance, applies a deposit, and then saves the new modified balance, where of course you’d want that to happen atomically.  If you read the balance, then go to save the new balance and between that time the previous balance has already changed, you’ll have an issue!  Think about it, if we read the current balance as $400, and we are applying a new deposit of $50.75, but meanwhile someone else deposits $200 and sets the total to $600, but then we write a total of $450.75 we’ve lost $200! Now, certainly for int and long values we can use Interlocked.Add() to handles these cases, and it works well for that.  But what if we want to work with doubles, for example?  Let’s say we wanted to add the numbers from 0 to 99,999 in parallel.  We could do this by spawning several parallel tasks to continuously add to a total: 1: double total = 0; 2:  3: Parallel.For(0, 10000, next => 4: { 5: total += next; 6: }); Were this run on one thread using a standard for loop, we’d expect an answer of 4,999,950,000 (the sum of all numbers from 0 to 99,999).  But when we run this in parallel as written above, we’ll likely get something far off.  The result of one of my runs, for example, was 1,281,880,740.  That is way off!  If this were banking software we’d be in big trouble with our clients.  So what happened?  The += operator is not atomic, it will read in the current value, add the result, then store it back into the total.  At any point in all of this another thread could read a “dirty” current total and accidentally “skip” our add.   So, to clean this up, we could use a lock to guarantee concurrency: 1: double total = 0.0; 2: object locker = new object(); 3:  4: Parallel.For(0, count, next => 5: { 6: lock (locker) 7: { 8: total += next; 9: } 10: }); Which will give us the correct result of 4,999,950,000.  One thing to note is that locking can be heavy, especially if the operation being locked over is trivial, or the life of the lock is a high percentage of the work being performed concurrently.  In the case above, the lock consumes pretty much all of the time of each parallel task – and the task being locked on is relatively trivial. Now, let me put in a disclaimer here before we go further: For most uses, lock is more than sufficient for your needs, and is often the simplest solution!    So, if lock is sufficient for most needs, why would we ever consider another solution?  The problem with locking is that it can suspend execution of your thread while it waits for the signal that the lock is free.  Moreover, if the operation being locked over is trivial, the lock can add a very high level of overhead.  This is why things like Interlocked.Increment() perform so well, instead of locking just to perform an increment, we perform the increment with an atomic, lockless method. As with all things performance related, it’s important to profile before jumping to the conclusion that you should optimize everything in your path.  If your profiling shows that locking is causing a high level of waiting in your application, then it’s time to consider lighter alternatives such as Interlocked. CompareExchange() – Exchange existing value if equal some value So let’s look at how we could use CompareExchange() to solve our problem above.  The general syntax of CompareExchange() is: T CompareExchange<T>(ref T location, T newValue, T expectedValue) If the value in location == expectedValue, then newValue is exchanged.  Either way, the value in location (before exchange) is returned. Actually, CompareExchange() is not one method, but a family of overloaded methods that can take int, long, float, double, pointers, or references.  It cannot take other value types (that is, can’t CompareExchange() two DateTime instances directly).  Also keep in mind that the version that takes any reference type (the generic overload) only checks for reference equality, it does not call any overridden Equals(). So how does this help us?  Well, we can grab the current total, and exchange the new value if total hasn’t changed.  This would look like this: 1: // grab the snapshot 2: double current = total; 3:  4: // if the total hasn’t changed since I grabbed the snapshot, then 5: // set it to the new total 6: Interlocked.CompareExchange(ref total, current + next, current); So what the code above says is: if the amount in total (1st arg) is the same as the amount in current (3rd arg), then set total to current + next (2nd arg).  This check and exchange pair is atomic (and thus thread-safe). This works if total is the same as our snapshot in current, but the problem, is what happens if they aren’t the same?  Well, we know that in either case we will get the previous value of total (before the exchange), back as a result.  Thus, we can test this against our snapshot to see if it was the value we expected: 1: // if the value returned is != current, then our snapshot must be out of date 2: // which means we didn't (and shouldn't) apply current + next 3: if (Interlocked.CompareExchange(ref total, current + next, current) != current) 4: { 5: // ooops, total was not equal to our snapshot in current, what should we do??? 6: } So what do we do if we fail?  That’s up to you and the problem you are trying to solve.  It’s possible you would decide to abort the whole transaction, or perhaps do a lightweight spin and try again.  Let’s try that: 1: double current = total; 2:  3: // make first attempt... 4: if (Interlocked.CompareExchange(ref total, current + i, current) != current) 5: { 6: // if we fail, go into a spin wait, spin, and try again until succeed 7: var spinner = new SpinWait(); 8:  9: do 10: { 11: spinner.SpinOnce(); 12: current = total; 13: } 14: while (Interlocked.CompareExchange(ref total, current + i, current) != current); 15: } 16:  This is not trivial code, but it illustrates a possible use of CompareExchange().  What we are doing is first checking to see if we succeed on the first try, and if so great!  If not, we create a SpinWait and then repeat the process of SpinOnce(), grab a fresh snapshot, and repeat until CompareExchnage() succeeds.  You may wonder why not a simple do-while here, and the reason it’s more efficient to only create the SpinWait until we absolutely know we need one, for optimal efficiency. Though not as simple (or maintainable) as a simple lock, this will perform better in many situations.  Comparing an unlocked (and wrong) version, a version using lock, and the Interlocked of the code, we get the following average times for multiple iterations of adding the sum of 100,000 numbers: 1: Unlocked money average time: 2.1 ms 2: Locked money average time: 5.1 ms 3: Interlocked money average time: 3 ms So the Interlocked.CompareExchange(), while heavier to code, came in lighter than the lock, offering a good compromise of safety and performance when we need to reduce contention. CompareExchange() - it’s not just for adding stuff… So that was one simple use of CompareExchange() in the context of adding double values -- which meant we couldn’t have used the simpler Interlocked.Add() -- but it has other uses as well. If you think about it, this really works anytime you want to create something new based on a current value without using a full lock.  For example, you could use it to create a simple lazy instantiation implementation.  In this case, we want to set the lazy instance only if the previous value was null: 1: public static class Lazy<T> where T : class, new() 2: { 3: private static T _instance; 4:  5: public static T Instance 6: { 7: get 8: { 9: // if current is null, we need to create new instance 10: if (_instance == null) 11: { 12: // attempt create, it will only set if previous was null 13: Interlocked.CompareExchange(ref _instance, new T(), (T)null); 14: } 15:  16: return _instance; 17: } 18: } 19: } So, if _instance == null, this will create a new T() and attempt to exchange it with _instance.  If _instance is not null, then it does nothing and we discard the new T() we created. This is a way to create lazy instances of a type where we are more concerned about locking overhead than creating an accidental duplicate which is not used.  In fact, the BCL implementation of Lazy<T> offers a similar thread-safety choice for Publication thread safety, where it will not guarantee only one instance was created, but it will guarantee that all readers get the same instance.  Another possible use would be in concurrent collections.  Let’s say, for example, that you are creating your own brand new super stack that uses a linked list paradigm and is “lock free”.  We could use Interlocked.CompareExchange() to be able to do a lockless Push() which could be more efficient in multi-threaded applications where several threads are pushing and popping on the stack concurrently. Yes, there are already concurrent collections in the BCL (in .NET 4.0 as part of the TPL), but it’s a fun exercise!  So let’s assume we have a node like this: 1: public sealed class Node<T> 2: { 3: // the data for this node 4: public T Data { get; set; } 5:  6: // the link to the next instance 7: internal Node<T> Next { get; set; } 8: } Then, perhaps, our stack’s Push() operation might look something like: 1: public sealed class SuperStack<T> 2: { 3: private volatile T _head; 4:  5: public void Push(T value) 6: { 7: var newNode = new Node<int> { Data = value, Next = _head }; 8:  9: if (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next) 10: { 11: var spinner = new SpinWait(); 12:  13: do 14: { 15: spinner.SpinOnce(); 16: newNode.Next = _head; 17: } 18: while (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next); 19: } 20: } 21:  22: // ... 23: } Notice a similar paradigm here as with adding our doubles before.  What we are doing is creating the new Node with the data to push, and with a Next value being the original node referenced by _head.  This will create our stack behavior (LIFO – Last In, First Out).  Now, we have to set _head to now refer to the newNode, but we must first make sure it hasn’t changed! So we check to see if _head has the same value we saved in our snapshot as newNode.Next, and if so, we set _head to newNode.  This is all done atomically, and the result is _head’s original value, as long as the original value was what we assumed it was with newNode.Next, then we are good and we set it without a lock!  If not, we SpinWait and try again. Once again, this is much lighter than locking in highly parallelized code with lots of contention.  If I compare the method above with a similar class using lock, I get the following results for pushing 100,000 items: 1: Locked SuperStack average time: 6 ms 2: Interlocked SuperStack average time: 4.5 ms So, once again, we can get more efficient than a lock, though there is the cost of added code complexity.  Fortunately for you, most of the concurrent collection you’d ever need are already created for you in the System.Collections.Concurrent (here) namespace – for more information, see my Little Wonders – The Concurent Collections Part 1 (here), Part 2 (here), and Part 3 (here). Summary We’ve seen before how the Interlocked class can be used to safely and efficiently add, increment, decrement, read, and exchange values in a multi-threaded environment.  In addition to these, Interlocked CompareExchange() can be used to perform more complex logic without the need of a lock when lock contention is a concern. The added efficiency, though, comes at the cost of more complex code.  As such, the standard lock is often sufficient for most thread-safety needs.  But if profiling indicates you spend a lot of time waiting for locks, or if you just need a lock for something simple such as an increment, decrement, read, exchange, etc., then consider using the Interlocked class’s methods to reduce wait. Technorati Tags: C#,CSharp,.NET,Little Wonders,Interlocked,CompareExchange,threading,concurrency

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  • Parsing Concerns

    - by Jesse
    If you’ve ever written an application that accepts date and/or time inputs from an external source (a person, an uploaded file, posted XML, etc.) then you’ve no doubt had to deal with parsing some text representing a date into a data structure that a computer can understand. Similarly, you’ve probably also had to take values from those same data structure and turn them back into their original formats. Most (all?) suitably modern development platforms expose some kind of parsing and formatting functionality for turning text into dates and vice versa. In .NET, the DateTime data structure exposes ‘Parse’ and ‘ToString’ methods for this purpose. This post will focus mostly on parsing, though most of the examples and suggestions below can also be applied to the ToString method. The DateTime.Parse method is pretty permissive in the values that it will accept (though apparently not as permissive as some other languages) which makes it pretty easy to take some text provided by a user and turn it into a proper DateTime instance. Here are some examples (note that the resulting DateTime values are shown using the RFC1123 format): DateTime.Parse("3/12/2010"); //Fri, 12 Mar 2010 00:00:00 GMT DateTime.Parse("2:00 AM"); //Sat, 01 Jan 2011 02:00:00 GMT (took today's date as date portion) DateTime.Parse("5-15/2010"); //Sat, 15 May 2010 00:00:00 GMT DateTime.Parse("7/8"); //Fri, 08 Jul 2011 00:00:00 GMT DateTime.Parse("Thursday, July 1, 2010"); //Thu, 01 Jul 2010 00:00:00 GMT Dealing With Inaccuracy While the DateTime struct has the ability to store a date and time value accurate down to the millisecond, most date strings provided by a user are not going to specify values with that much precision. In each of the above examples, the Parse method was provided a partial value from which to construct a proper DateTime. This means it had to go ahead and assume what you meant and fill in the missing parts of the date and time for you. This is a good thing, especially when we’re talking about taking input from a user. We can’t expect that every person using our software to provide a year, day, month, hour, minute, second, and millisecond every time they need to express a date. That said, it’s important for developers to understand what assumptions the software might be making and plan accordingly. I think the assumptions that were made in each of the above examples were pretty reasonable, though if we dig into this method a little bit deeper we’ll find that there are a lot more assumptions being made under the covers than you might have previously known. One of the biggest assumptions that the DateTime.Parse method has to make relates to the format of the date represented by the provided string. Let’s consider this example input string: ‘10-02-15’. To some people. that might look like ‘15-Feb-2010’. To others, it might be ‘02-Oct-2015’. Like many things, it depends on where you’re from. This Is America! Most cultures around the world have adopted a “little-endian” or “big-endian” formats. (Source: Date And Time Notation By Country) In this context,  a “little-endian” date format would list the date parts with the least significant first while the “big-endian” date format would list them with the most significant first. For example, a “little-endian” date would be “day-month-year” and “big-endian” would be “year-month-day”. It’s worth nothing here that ISO 8601 defines a “big-endian” format as the international standard. While I personally prefer “big-endian” style date formats, I think both styles make sense in that they follow some logical standard with respect to ordering the date parts by their significance. Here in the United States, however, we buck that trend by using what is, in comparison, a completely nonsensical format of “month/day/year”. Almost no other country in the world uses this format. I’ve been fortunate in my life to have done some international travel, so I’ve been aware of this difference for many years, but never really thought much about it. Until recently, I had been developing software for exclusively US-based audiences and remained blissfully ignorant of the different date formats employed by other countries around the world. The web application I work on is being rolled out to users in different countries, so I was recently tasked with updating it to support different date formats. As it turns out, .NET has a great mechanism for dealing with different date formats right out of the box. Supporting date formats for different cultures is actually pretty easy once you understand this mechanism. Pulling the Curtain Back On the Parse Method Have you ever taken a look at the different flavors (read: overloads) that the DateTime.Parse method comes in? In it’s simplest form, it takes a single string parameter and returns the corresponding DateTime value (if it can divine what the date value should be). You can optionally provide two additional parameters to this method: an ‘System.IFormatProvider’ and a ‘System.Globalization.DateTimeStyles’. Both of these optional parameters have some bearing on the assumptions that get made while parsing a date, but for the purposes of this article I’m going to focus on the ‘System.IFormatProvider’ parameter. The IFormatProvider exposes a single method called ‘GetFormat’ that returns an object to be used for determining the proper format for displaying and parsing things like numbers and dates. This interface plays a big role in the globalization capabilities that are built into the .NET Framework. The cornerstone of these globalization capabilities can be found in the ‘System.Globalization.CultureInfo’ class. To put it simply, the CultureInfo class is used to encapsulate information related to things like language, writing system, and date formats for a certain culture. Support for many cultures are “baked in” to the .NET Framework and there is capacity for defining custom cultures if needed (thought I’ve never delved into that). While the details of the CultureInfo class are beyond the scope of this post, so for now let me just point out that the CultureInfo class implements the IFormatInfo interface. This means that a CultureInfo instance created for a given culture can be provided to the DateTime.Parse method in order to tell it what date formats it should expect. So what happens when you don’t provide this value? Let’s crack this method open in Reflector: When no IFormatInfo parameter is provided (i.e. we use the simple DateTime.Parse(string) overload), the ‘DateTimeFormatInfo.CurrentInfo’ is used instead. Drilling down a bit further we can see the implementation of the DateTimeFormatInfo.CurrentInfo property: From this property we can determine that, in the absence of an IFormatProvider being specified, the DateTime.Parse method will assume that the provided date should be treated as if it were in the format defined by the CultureInfo object that is attached to the current thread. The culture specified by the CultureInfo instance on the current thread can vary depending on several factors, but if you’re writing an application where a single instance might be used by people from different cultures (i.e. a web application with an international user base), it’s important to know what this value is. Having a solid strategy for setting the current thread’s culture for each incoming request in an internationally used ASP .NET application is obviously important, and might make a good topic for a future post. For now, let’s think about what the implications of not having the correct culture set on the current thread. Let’s say you’re running an ASP .NET application on a server in the United States. The server was setup by English speakers in the United States, so it’s configured for US English. It exposes a web page where users can enter order data, one piece of which is an anticipated order delivery date. Most users are in the US, and therefore enter dates in a ‘month/day/year’ format. The application is using the DateTime.Parse(string) method to turn the values provided by the user into actual DateTime instances that can be stored in the database. This all works fine, because your users and your server both think of dates in the same way. Now you need to support some users in South America, where a ‘day/month/year’ format is used. The best case scenario at this point is a user will enter March 13, 2011 as ‘25/03/2011’. This would cause the call to DateTime.Parse to blow up since that value doesn’t look like a valid date in the US English culture (Note: In all likelihood you might be using the DateTime.TryParse(string) method here instead, but that method behaves the same way with regard to date formats). “But wait a minute”, you might be saying to yourself, “I thought you said that this was the best case scenario?” This scenario would prevent users from entering orders in the system, which is bad, but it could be worse! What if the order needs to be delivered a day earlier than that, on March 12, 2011? Now the user enters ‘12/03/2011’. Now the call to DateTime.Parse sees what it thinks is a valid date, but there’s just one problem: it’s not the right date. Now this order won’t get delivered until December 3, 2011. In my opinion, that kind of data corruption is a much bigger problem than having the Parse call fail. What To Do? My order entry example is a bit contrived, but I think it serves to illustrate the potential issues with accepting date input from users. There are some approaches you can take to make this easier on you and your users: Eliminate ambiguity by using a graphical date input control. I’m personally a fan of a jQuery UI Datepicker widget. It’s pretty easy to setup, can be themed to match the look and feel of your site, and has support for multiple languages and cultures. Be sure you have a way to track the culture preference of each user in your system. For a web application this could be done using something like a cookie or session state variable. Ensure that the current user’s culture is being applied correctly to DateTime formatting and parsing code. This can be accomplished by ensuring that each request has the handling thread’s CultureInfo set properly, or by using the Format and Parse method overloads that accept an IFormatProvider instance where the provided value is a CultureInfo object constructed using the current user’s culture preference. When in doubt, favor formats that are internationally recognizable. Using the string ‘2010-03-05’ is likely to be recognized as March, 5 2011 by users from most (if not all) cultures. Favor standard date format strings over custom ones. So far we’ve only talked about turning a string into a DateTime, but most of the same “gotchas” apply when doing the opposite. Consider this code: someDateValue.ToString("MM/dd/yyyy"); This will output the same string regardless of what the current thread’s culture is set to (with the exception of some cultures that don’t use the Gregorian calendar system, but that’s another issue all together). For displaying dates to users, it would be better to do this: someDateValue.ToString("d"); This standard format string of “d” will use the “short date format” as defined by the culture attached to the current thread (or provided in the IFormatProvider instance in the proper method overload). This means that it will honor the proper month/day/year, year/month/day, or day/month/year format for the culture. Knowing Your Audience The examples and suggestions shown above can go a long way toward getting an application in shape for dealing with date inputs from users in multiple cultures. There are some instances, however, where taking approaches like these would not be appropriate. In some cases, the provider or consumer of date values that pass through your application are not people, but other applications (or other portions of your own application). For example, if your site has a page that accepts a date as a query string parameter, you’ll probably want to format that date using invariant date format. Otherwise, the same URL could end up evaluating to a different page depending on the user that is viewing it. In addition, if your application exports data for consumption by other systems, it’s best to have an agreed upon format that all systems can use and that will not vary depending upon whether or not the users of the systems on either side prefer a month/day/year or day/month/year format. I’ll look more at some approaches for dealing with these situations in a future post. If you take away one thing from this post, make it an understanding of the importance of knowing where the dates that pass through your system come from and are going to. You will likely want to vary your parsing and formatting approach depending on your audience.

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  • Linux VirtualBox inside Windows VirtualBox doesn't boot

    - by Tobbe
    I'm trying to run a Linux VirtualBox instance inside a Windows 7 VirtualBox instance, but Linux (tried both Puppy and Mint) doesn't boot. My research says that this should be possible, see here for example: Can you run one virtual machine inside another? but I can't get it to work. Here are a couple of screenshots showing where the boot process stops for Linux Mint and Puppy Linux. What am I doing wrong?

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  • Bind an ip address to Postfix as outgoing ip

    - by jack
    Is that possible to bind all available public ip addresses on a server to one Postfix instance as its outgoing ip pool and let it choose a random ip or specified ip from the pool each time it sends out an email? If above is not possible, can it be configured to listen on one public ip address per instance and each time it delivers a message, it use the binded one as outgoing ip address.

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  • Can IBM IHS server support more than one Websphere Application Server plug-in location?

    - by Spike Williams
    We want http://webserver.com/foo to point to an instance of WAS 6.0, and http://webserver.com/foo2 to point to an instance of WAS 7.0, running on the same server, but with different port numbers. This is a temporary thing, as we need to have both servers running as we transition our applications from running on 6.0 to 7.0. The webserver is IBMIHS (an Apache variant), and it needs to use the WebSphere plugin to connect to the WAS servers. Will this work? Any drawbacks?

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  • robocopy transfer file and not folder

    - by Bill McKay
    I'm trying to use robocopy to tranfer a single file from one location to another but robocopy seems to think I'm always specifying a folder. Here is an example: robocopy "c:\transfer_this.txt" "z:\transferred.txt" But I get this error instead: 2009/08/11 15:21:57 ERROR 123 (0x0000007B) Accessing Source Directory c:\transfer_this.txt\ (note the '\' at the end of transfer_this.txt) But if I treat it like an entire folder: robocopy "c:\folder" "z:\folder" It works but then I have to transfer everything in the folder. How can I only transfer a single file with robocopy?

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  • How do I create multiple instances of Certificate Server on the same Windows installation?

    - by makerofthings7
    The following URLs describe a new feature of Windows Certificate server is the ability to install multiple instances on the same server. (see end of "transcript" link it's a zip file) http://www.digitalsupporttech.com/mskb/896/896733_TechNet_Support_WebCast:_Best_Practices_for_Public_Key_Infrastructure:_Steps_to_build_an_offline_root_certification_authority_%28part_1_of_2%29.htm Quote: "Multiple Certificate Server instances on a single physical server" http://winintro.ru/certsvr.en/html/cf5622e1-daa9-42cc-8b43-14953e34f8b6.htm Quote: "Multiple instances of the Certificate Enrollment Web Service can be installed on a single computer in order to support multiple CAs." Question How can I actually implement multiple CA instances on a Windows 2008R2 server?

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  • How do you transfer AWS RDS snap shot to a different AWS account

    - by Webmonger
    Hi I have an RDS database that I need to transfer a snapshot of to another AWS account. I understand there are issues being able to do this between availability zones so I'm really unsure if this is possible. The RDS instance is mySql. If it's not possible to transfer the snapshot please could you explain how to transfer the data from one RDS instance to another without downloading any if the contents(The DB is over 200GB). Thanks in advance

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  • Prevent gnome from automatically mounting partition when clicked in nautilus

    - by bjarkef
    Hi, I have two partitions on a hard drive in my machine that are formatted as ntfs, but must under no circumstance be mounted by my Ubuntu installation (unless I do some preparation first). However nautilus happily displays the partitions, and a single click will mount them automatically. This is very dangerous behaviour, how can I hide the partitions from nautilus and prevent accidentally mounting them by a single stray mouse click? Thanks

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  • Using multiple domain names on same server

    - by TheVillageIdiot
    Hi, I'm developing a website where users will be able to aggregate their RSS feeds and create custom pages. I want to give each user separate domain name like jonhdoe.com, xyz.org. I'll be keeping files on single server in one web application (I don't want to replace all the api for all users). Now the question: How can I make multiple domain names point to single web site?

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  • How to see if turbo boost is working on I7 860 CPU?

    - by Jan Derk
    I just build myself a new system with a Intel I7 860 CPU. When loading it using a single threaded application like Super PI, CPU-Z shows 2.933Ghz as speed. Now I understood that the I7 goes into turbo boost mode up to 3.46GHz for a single core. How can I check that? Is there a utility to monitor CPU speed per core?

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  • How do I stop VMware Workstation 6.5 from giving up input focus for no reason on Ubuntu 10.4?

    - by Matt
    After patching some kernel modules, I got VMware Workstation 6.5.4 running on my Ubuntu 10.4 x86_64 machine. However, now my Windows XP SP3 guest instance cannot keep mouse input captured for any length of time. I can sometimes activate a control in the guest if a double click very quickly, but it's not reliable (and extremely annoying). Everything appears to be fine in Unity; the problem just appears when I'm running the instance in the VMware window.

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  • SQuirrelSQL redirect ouput to a file?

    - by Oscar Reyes
    Does anybody knows if SQuirrel SQL client may output the of several SQL commands to a single result window in textplain or to a file ( as SQL+ would ) So I can: select * from dual; select * from dual; And have both results in a single "ready to" Ctrl-C format?

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  • Load balancing with 2 wireless cards

    - by user2544786
    I'm thinking about building a wireless load balancer (if that makes sense). For example, the first wireless card will accept all connections for ip 192.168.1.1 and the second card will serve requests for 192.168.1.2. I know that I can assign both IPs to a single card and all requests will be served by a single wireless card. Would it be better (more bandwidth, more stable connection, etc?) to have two physical cards instead?

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  • How do I parse file paths separated by a space in a string?

    - by user1130637
    Background: I am working in Automator on a wrapper to a command line utility. I need a way to separate an arbitrary number of file paths delimited by a single space from a single string, so that I may remove all but the first file path to pass to the program. Example input string: /Users/bobby/diddy dum/ding.mp4 /Users/jimmy/gone mia/come back jimmy.mp3 ... Desired output: /Users/bobby/diddy dum/ding.mp4 Part of the problem is the inflexibility on the Automator end of things. I'm using an Automator action which returns unescaped POSIX filepaths delimited by a space (or comma). This is unfortunate because: 1. I cannot ensure file/folder names will not contain either a space or comma, and 2. the only inadmissible character in Mac OS X filenames (as far as I can tell) is :. There are options which allow me to enclose the file paths in double or single quotes, or angle brackets. The program itself accepts the argument of the aforementioned input string, so there must be a way of separating the paths. I just do not have a keen enough eye to see how to do it with sed or awk. At first I thought I'll just use sed to replace every [space]/ with [newline]/ and then trim all but the first line, but that leaves the loophole open for folders whose names end with a space. If I use the comma delimiter, the same happens, just for a comma instead. If I encapsulate in double or single quotation marks, I am opening another can of worms for filenames with those characters. The image/link is the relevant part of my Automator workflow. -- UPDATE -- I was able to achieve what I wanted in a rather roundabout way. It's hardly elegant but here is working generalized code: path="/Users/bobby/diddy dum/ding.mp4 /Users/jimmy/gone mia/come back jimmy.mp3" # using colon because it's an inadmissible Mac OS X # filename character, perfect for separating # also, unlike [space], multiple colons do not collapse IFS=: # replace all spaces with colons colpath=$(echo "$path" | sed 's/ /:/g') # place words from colon-ized file path into array # e.g. three spaces -> three colons -> two empty words j=1 for word in $colpath do filearray[$j]="$word" j=$j+1 done # reconstruct file path word by word # after each addition, check file existence # if non-existent, re-add lost [space] and continue until found name="" for seg in "${filearray[@]}" do name="$name$seg" if [[ -f "$name" ]] then echo "$name" break fi name="$name " done All this trouble because the default IFS doesn't count "emptiness" between the spaces as words, but rather collapses them all.

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  • Merge tabs from 2 session of IE8?

    - by MattSlay
    Sometimes I wind up with two or more instances of IE8 running, and each instance has a few tabs open. Is there a way to merge all the tabs from all the IE8 instances into just one instance of IE8, and close all the other IE8 instances?

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  • Multiple access points for the same SSID ?

    - by krosenvold
    I need to upgrade my existing wireless infrastructure and this time I want 2 access points to cover my house, since I get blind spots no matter what with a single AP, I have physical cabling to my central network available for both access points. But I would really like these two to interoperate seamlessly as a single SSID. How do I do this and what are the features the new AP's I'm buying need to support ? (Product recommendations are welcome ;)

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  • SQL Server Moved Active Directory Domain

    - by Ollie
    I have changed the AD domain on a SQL Server 2008 box which was setup only for Windows Authentication. Now the domain has changed, I can't log into the SQL Server instance even as the domain's Administrator account. Is there a way of updating the server security settings without logging into the SQL instance first through a command switch / registry setting / etc..

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  • How does Windows Task Scheduler detect that a task is already running?

    - by Dan C
    I have an application on Windows Server 2008 that takes different command-line parameters. For example: myapp.exe /A myapp.exe /B I have created a task scheduler task for each of those. While "myapp.exe /A" is running, I want to prevent another instance of it from starting. However, I still want "myapp.exe /B" to be able to run (again, though only one instance of it at a time). How can I set this up?

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  • Are FC and SAS DAS devices standard enough?

    - by user222182
    Before I ask my questions, here is some background info that may or may not be useful: For the first time I find myself needing a DAS solution. My priority is data through-put in a single direction. I can write large blocks, and I don't need to read at the same time. The server (the data producing device) is not really a typical server, its a very powerful single board computer. As such I have limited options when it comes to the add-in cards I can install since it must use the fairly uncommon interface, XMC. Currently I believe I am limited PCIex8 gen 1 which means that the likely bottle neck for me will be this 16gbps connection. XMC Boards I have found so far offer the following connections: a) Dual 10GBE ethernet controller, total throughput 20gbps b) Dual Quad SAS 2.0 Connectors (SFF-8XXX) HBA (no raid), total throughput 48 gbps c) Dual FC 8gb HBA (no raid), total throughput 16gbps My questions for you guys are: 1) Are SAS and/or FC, and by extension their HBAs, standard enough that I could purchase a Dell or Aberdeen storage server with a raid controller that has external SAS or FC ports and expect that I can connect it to my SAS or FC HBA, be presented with a single volume (if I so configured the storage server), all without having to check for HBA compatibility? 2) On a device like a Dell PowerVault (either DAS or NAS) is there an OS on it to concern myself with, or is it meant to be remotely managed? Is there a local interface in case I cant remotely manage it (i.e. if my single board computer uses an OS not supported by Dell OpenManage). Would this be true of nearly any device which calls itself a DAS? 3) If I purchase some sort of Supermicro storage chassis, installed a raid controller with external connections, is there a nice lightweight OS I can run just for management of the controller? Would I even need an OS since the raid card would be configured pre-boot anyway? 4) It is much easier to buy XMC based 10gigabit ethernet cards (generally dual port). In what ways would I be getting into trouble by using iSCSI as a DAS are direct cabling with SFP+ cables? Thanks in advance

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  • mysqld_multi stop doesn't seem to work

    - by gravyface
    mysqld_multi stop 1 followed by (repeatedly, a few moments later) mysqld_multi report 1 returns: Reporting MySQL servers MySQL server from group: mysqld1 is running The instances work fine and when I reboot, I have to start the instances to get them to come back up (a separate issue I need to resolve), but the stop command doesn't seem to do anything. It truly doesn't stop the instance because in the instance log file I see this: 120619 11:12:39 mysqld_safe A mysqld process already exists after trying to run start after.

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