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• How to produce precisely-timed tone and silence in C#

  - by Bob Denny

  I have a C# project that plays Morse code for RSS feeds. I write it using Managed DirectX, only to discover that Managed DirectX is old and deprecated. The task I have is to play pure sine wave bursts interspersed with silence periods (the code) which are precisely timed as to their duration. I need to be able to call a function which plays a pure tone for so many milliseconds, then Thread.Sleep() then play another, etc. At its fastest, the tones and spaces can be as short as 40ms. It's working quite well in Managed DirectX. To get the precisely timed tone I create 1 sec. of sine wave into a secondary buffer, then to play a tone of a certain duration I seek forward to within x milliseconds of the end of the buffer then play. I've tried System.Media.SoundPlayer. It's a loser because you have to Play(), Sleep(), then Stop() for arbitrary tone lengths. The result is a tone that is too long, variable by CPU load. It takes an indeterminate amount of time to actually stop the tone. I then embarked on a lengthy attempt to use NAudio 1.3. I ended up with a memory resident stream providing the tone data, and again seeking forward leaving the desired length of tone remaining in the stream, then playing. This worked OK on the DirectSoundOut class for a while (see below) but the WaveOut class quickly dies with an internal assert saying that buffers are still on the queue despite PlayerStopped = true. This is odd since I play to the end then put a wait of the same duration between the end of the tone and the start of the next. You'd think that 80ms after starting Play of a 40 ms tone that it wouldn't have buffers on the queue. DirectSoundOut works well for a while, but its problem is that for every tone burst Play() it spins off a separate thread. Eventually (5 min or so) it just stops working. You can see thread after thread after thread exiting in the Output window while running the project in VS2008 IDE. I don't create new objects during playing, I just Seek() the tone stream then call Play() over and over, so I don't think it's a problem with orphaned buffers/whatever piling up till it's choked. I'm out of patience on this one, so I'm asking in the hopes that someone here has faced a similar requirement and can steer me in a direction with a likely solution. Thanks in advance...

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• Mock static method Activator.CreateInstance to return a mock of another class

  - by Jeep87c

  I have this factory class and I want to test it correctly. Let's say I have an abstract class which have many child (inheritance). As you can see in my Factory class the method BuildChild, I want to be able to create an instance of a child class at Runtime. I must be able to create this instance during Runtime because the type won't be know before runtime. And, I can NOT use Unity for this project (if so, I would not ask how to achieve this). Here's my Factory class that I want to test: public class Factory { public AnAbstractClass BuildChild(Type childType, object parameter) { AnAbstractClass child = (AnAbstractClass) Activator.CreateInstance(childType); child.Initialize(parameter); return child; } } To test this, I want to find a way to Mock Activator.CreateInstance to return my own mocked object of a child class. How can I achieve this? Or maybe if you have a better way to do this without using Activator.CreateInstance (and Unity), I'm opened to it if it's easier to test and mock! I'm currently using Moq to create my mocks but since Activator.CreateInstance is a static method from a static class, I can't figure out how to do this (I already know that Moq can only create mock instances of objects). I took a look at Fakes from Microsoft but without success (I had some difficulties to understand how it works and to find some well explained examples). Please help me! EDIT: I need to mock Activator.CreateInstance because I want to force this method to return another mocked object. The correct thing I want is only to stub this method (not to mock it). So when I test BuildChild like this: [TestMethod] public void TestBuildChild() { var mockChildClass = new Mock(AChildClass); // TODO: Stub/Mock Activator.CreateInstance to return mockChildClass when called with "type" and "parameter" as follow. var type = typeof(AChildClass); var parameter = "A parameter"; var child = this._factory.BuildChild(type, parameters); } Activator.CreateInstance called with type and parameter will return my mocked object instead of creating a new instance of the real child class (not yet implemented).

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• How do I serialize an object to xml but not have it be the root element of the xml document

  - by mezoid

  I have the following object: public class MyClass { public int Id { get; set;} public string Name { get; set; } } I'm wanting to serialize this to the following xml string: <MyClass> <Id>1</Id> <Name>My Name</Name> </MyClass> Unfortunately, when I use the XMLSerializer I get a string which looks like: <?xml version="1.0" encoding="utf-8"?> <MyClass xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <Id>1</Id> <Name>My Name</Name> </MyClass> I'm not wanting MyClass to be the root element the document, rather I'm eventually wanting to add the string with other similar serialized objects which will be within a larger xml document. i.e. Eventually I'll have a xml string which looks like this: <Classes> <MyClass> <Id>1</Id> <Name>My Name</Name> </MyClass> <MyClass> <Id>1</Id> <Name>My Name</Name> </MyClass> </Classes>" My first thought was to create a class as follows: public class Classes { public List<MyClass> MyClasses { get; set; } } ...but that just addes an additional node called MyClasses to wrap the list of MyClass.... My gut feeling is that I'm approaching this the wrong way and that my lack of experience with creating xml files isn't helping to point me to some part of the .NET framework or some other library that simplifies this.

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• Winform radiobutton data binding

  - by Rajarshi

  I am following the "Presentation Model" design pattern suggested by Martin Fowler for my GUI architecture in a Windows Forms project. "The essence of a Presentation Model is of a fully self-contained class that represents all the data and behavior of the UI window, but without any of the controls used to render that UI on the screen. A view then simply projects the state of the presentation model onto the glass...." - Martin Fowler Read more about this pattern at www.martinfowler.com/eaaDev/PresentationModel.html I am finding the concept very fluid and easy to understand except this one issue of data binding RadioButtons to properties on the Data/Domain object. Suposing I have a Windows Form with 3 radio buttons to depict some "Mode" options as - Auto Manual Import How can I use boolean properties on Data/Domain Objects to DataBind to these buttons? I have tried many ways but to no avail. For example I would like to code like - rbtnAutoMode.DataBindings.Add("Text", myBusinessObject, "IsAutoMode"); rbtnManualMode.DataBindings.Add("Text", myBusinessObject, "IsManualMode"); rbtnImportMode.DataBindings.Add("Text", myBusinessObject, "IsImportMode"); There should be a fourth property like "SelectedMode" on the data/domain object which at the end should depict a single value like "SelectedMode = Auto". I am trying to update this property when any of the "IsAutoMode", "IsManualMode" or "IsImportMode" is changed, e.g. through the property setters. I have INotifyPropertyChanged implemented on my data/domain object so, updating any data/domain object property automatically updates my UI controls, that's not an issue. There is a good example of binding 2 radio buttons here - http://stackoverflow.com/questions/344964/how-do-i-use-databinding-with-windows-forms-radio-buttons but I am missing the link while implementing the same with 3 buttons. I am having very erratic behaviors for the Radio Buttons. I hope I was able to explain reasonably. I am actually in a hurry and could not put a detailed code on post, but any help in this regard is appreciated. There is a simple solution to this issue by exposing a method like - public void SetMode(Modes mode) { this._selectedMode = mode; } which could be called from the "CheckedChanged" event of the Radio Buttons from the UI and would perfectly set the "SelectedMode" on the business object, but I need to stretch the limits to verify whether this can be done by DataBinding.

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• Is this (Lock-Free) Queue Implementation Thread-Safe?

  - by Hosam Aly

  I am trying to create a lock-free queue implementation in Java, mainly for personal learning. The queue should be a general one, allowing any number of readers and/or writers concurrently. Would you please review it, and suggest any improvements/issues you find? Thank you. import java.util.concurrent.atomic.AtomicReference; public class LockFreeQueue<T> { private static class Node<E> { E value; volatile Node<E> next; Node(E value) { this.value = value; } } private AtomicReference<Node<T>> head, tail; public LockFreeQueue() { // have both head and tail point to a dummy node Node<T> dummyNode = new Node<T>(null); head = new AtomicReference<Node<T>>(dummyNode); tail = new AtomicReference<Node<T>>(dummyNode); } /** * Puts an object at the end of the queue. */ public void putObject(T value) { Node<T> newNode = new Node<T>(value); Node<T> prevTailNode = tail.getAndSet(newNode); prevTailNode.next = newNode; } /** * Gets an object from the beginning of the queue. The object is removed * from the queue. If there are no objects in the queue, returns null. */ public T getObject() { Node<T> headNode, valueNode; // move head node to the next node using atomic semantics // as long as next node is not null do { headNode = head.get(); valueNode = headNode.next; // try until the whole loop executes pseudo-atomically // (i.e. unaffected by modifications done by other threads) } while (valueNode != null && !head.compareAndSet(headNode, valueNode)); T value = (valueNode != null ? valueNode.value : null); // release the value pointed to by head, keeping the head node dummy if (valueNode != null) valueNode.value = null; return value; }

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• Use native HBitmap in C# while preserving alpha channel/transparency. Please check this code, it works on my computer...

  - by David

  Let's say I get a HBITMAP object/handle from a native Windows function. I can convert it to a managed bitmap using Bitmap.FromHbitmap(nativeHBitmap), but if the native image has transparency information (alpha channel), it is lost by this conversion. There are a few questions on Stack Overflow regarding this issue. Using information from the first answer of this question (How to draw ARGB bitmap using GDI+?), I wrote a piece of code that I've tried and it works. It basically gets the native HBitmap width, height and the pointer to the location of the pixel data using GetObject and the BITMAP structure, and then calls the managed Bitmap constructor: Bitmap managedBitmap = new Bitmap(bitmapStruct.bmWidth, bitmapStruct.bmHeight, bitmapStruct.bmWidth * 4, PixelFormat.Format32bppArgb, bitmapStruct.bmBits); As I understand (please correct me if I'm wrong), this does not copy the actual pixel data from the native HBitmap to the managed bitmap, it simply points the managed bitmap to the pixel data from the native HBitmap. And I don't draw the bitmap here on another Graphics (DC) or on another bitmap, to avoid unnecessary memory copying, especially for large bitmaps. I can simply assign this bitmap to a PictureBox control or the the Form BackgroundImage property. And it works, the bitmap is displayed correctly, using transparency. When I no longer use the bitmap, I make sure the BackgroundImage property is no longer pointing to the bitmap, and I dispose both the managed bitmap and the native HBitmap. The Question: Can you tell me if this reasoning and code seems correct. I hope I will not get some unexpected behaviors or errors. And I hope I'm freeing all the memory and objects correctly. private void Example() { IntPtr nativeHBitmap = IntPtr.Zero; /* Get the native HBitmap object from a Windows function here */ // Create the BITMAP structure and get info from our nativeHBitmap NativeMethods.BITMAP bitmapStruct = new NativeMethods.BITMAP(); NativeMethods.GetObjectBitmap(nativeHBitmap, Marshal.SizeOf(bitmapStruct), ref bitmapStruct); // Create the managed bitmap using the pointer to the pixel data of the native HBitmap Bitmap managedBitmap = new Bitmap( bitmapStruct.bmWidth, bitmapStruct.bmHeight, bitmapStruct.bmWidth * 4, PixelFormat.Format32bppArgb, bitmapStruct.bmBits); // Show the bitmap this.BackgroundImage = managedBitmap; /* Run the program, use the image */ MessageBox.Show("running..."); // When the image is no longer needed, dispose both the managed Bitmap object and the native HBitmap this.BackgroundImage = null; managedBitmap.Dispose(); NativeMethods.DeleteObject(nativeHBitmap); } internal static class NativeMethods { [StructLayout(LayoutKind.Sequential)] public struct BITMAP { public int bmType; public int bmWidth; public int bmHeight; public int bmWidthBytes; public ushort bmPlanes; public ushort bmBitsPixel; public IntPtr bmBits; } [DllImport("gdi32", CharSet = CharSet.Auto, EntryPoint = "GetObject")] public static extern int GetObjectBitmap(IntPtr hObject, int nCount, ref BITMAP lpObject); [DllImport("gdi32.dll")] internal static extern bool DeleteObject(IntPtr hObject); }

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• More advanced usage of interfaces

  - by owca

  To be honest I'm not quite sure if I understand the task myself :) I was told to create class MySimpleIt, that implements Iterator and Iterable and will allow to run the provided test code. Arguments and variables of objects cannot be either Collections or arrays. The code : MySimpleIt msi=new MySimple(10,100, MySimpleIt.PRIME_NUMBERS); for(int el: msi) System.out.print(el+" "); System.out.println(); msi.setType(MySimpleIterator.ODD_NUMBERS); msi.setLimits(15,30); for(int el: msi) System.out.print(el+" "); System.out.println(); msi.setType(MySimpleIterator.EVEN_NUMBERS); for(int el: msi) System.out.print(el+" "); System.out.println(); The result I should obtain : 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 15 17 19 21 23 25 27 29 16 18 20 22 24 26 28 30 And here's my code : import java.util.Iterator; interface MySimpleIterator{ static int ODD_NUMBERS=0; static int EVEN_NUMBERS = 1; static int PRIME_NUMBERS = 2; int setType(int i); } public class MySimpleIt implements Iterable, Iterator, MySimpleIterator { public MySimple my; public MySimpleIt(MySimple m){ my = m; } public int setType(int i){ my.numbers = i; return my.numbers; } public void setLimits(int d, int u){ my.down = d; my.up = u; } public Iterator iterator(){ Iterator it = this.iterator(); return it; } public void remove(){ } public Object next(){ Object o = new Object(); return o; } public boolean hasNext(){ return true; } } class MySimple { public int down; public int up; public int numbers; public MySimple(int d, int u, int n){ down = d; up = u; numbers = n; } } In the test code I have error in line when creating MySimpleIt msi object, as it finds MySimple instead of MySimpleIt. Also I have errors in for-each loops, because compiler wants 'ints' there instead of Object. Anyone has any idea on how to solve it ?

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• VB6 app not executing as scheduled task unless user is logged on

  - by Tedd Hansen

  Hi Would greatly apprechiate some help on this one! It may be a tricky one. :) Problem I have an VB6 application which is set up as scheduled task. It starts every time, but when executing CreateObject it fails if user is not logged on to computer. I am looking for information on what could cause this. Primary suspicion is that some Windows API fails. Key points Behaviour confirmed on Windows 2000, 2003, 2008 and Vista. The application executes as user X at scheduled time, executed by Windows Task Scheduler. It executes every time. Application does start! -- If user X is logged on via RDP it runs perfectly. (Note that user doesn't need to be connected, only logged on) -- If user X is not logged on to computer the application fails. Failure point Application fails when using CreateObject() to instansiate a DCOM object which is also part of the application. The DCOM objects declare .dll-references at startup (globally/on top of .bas-file) and run a small startup function. Failure must be during startup, possibly in one of the .dll-declarations. Thoughts After some Googling my initial suspicion was directed at MAPI. From what I could see MAPI required user to be logged on. The application has MAPI references. But even with all MAPI references removed it still does not work. What is the difference if an user is logged on? Registry mapping? Environment? explorer.exe is running. Isn't the user logged on when application executes as the user? What info would help? A definitive answer would be truly great. Any information regarding any VB6 feature/Windows API that could act differently depending on wether user is logged on or not would definitively help. Similar experiences may lead me in the right direction. Tips on debuggin this. Thanks! :)

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• WPF - How do I get an object that is bound to a ListBoxItem back

  - by JonBlumfeld

  Hi there here is what I would like to do. I get a List of objects from a database and bind this list to a ListBox Control. The ListBoxItems consist of a textbox and a button. Here is what I came up with. Up to this point it works as intended. The object has a number of Properties like ID, Name. If I click on the button in the ListBoxItem the Item should be erased from the ListBox and also from the database... <ListBox x:Name="taglistBox"> <ListBox.ItemContainerStyle> <Style TargetType="{x:Type ListBoxItem}"> <Setter Property="HorizontalAlignment" Value="Stretch"/> <Setter Property="Template"> <Setter.Value> <ControlTemplate TargetType="ListBoxItem"> <ContentPresenter HorizontalAlignment="Stretch"/> </ControlTemplate> </Setter.Value> </Setter> <Setter Property="Tag" Value="{Binding TagSelf}"></Setter> </Style> </ListBox.ItemContainerStyle> <ListBox.ItemTemplate> <DataTemplate> <Grid HorizontalAlignment="Stretch"> <Grid.ColumnDefinitions> <ColumnDefinition Width="Auto"/> <ColumnDefinition/> </Grid.ColumnDefinitions> <Button Grid.Column="0" Name="btTag" VerticalAlignment="Center" Click="btTag_Click" HorizontalAlignment="Left"> <Image Width="16" Height="16" Source="/WpfApplication1;component/Resources/104.png"/> </Button> <TextBlock Name="tbtagBoxTagItem" Margin="5" Grid.Column="1" Text="{Binding Name}" VerticalAlignment="Center" /> </Grid> </DataTemplate> </ListBox.ItemTemplate> </ListBox> The Textblock.Text is bound to object.Name and the ListBoxItem.Tag to object.TagSelf (which is just a copy of the object itself). Now my questions If I click the button in the listboxItem how do I get the listboxitem and the object bound to it back. In order to delete the object from the database I have to retrieve it somehow. I tried something like ListBoxItem lbi1 = (ListBoxItem)(taglistBox.ItemContainerGenerator.ContainerFromItem(taglistBox.Items.CurrentItem)); ObjectInQuestion t = (ObjectInQuestion) lbi1.Tag; Is there a way to automatically update the contents of the ListBox if the Itemssource changes? Right now I'm achieving that by taglistBox.ItemsSource = null; taglistBox.ItemsSource = ObjectInQuestion; I'd appreciate any help you can give :D Thanks in advance

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• RSpec mocking a nested model in Rails - ActionController problem

  - by emson

  Hi All I am having a problem in RSpec when my mock object is asked for a URL by the ActionController. The URL is a Mock one and not a correct resource URL. I am running RSpec 1.3.0 and Rails 2.3.5 Basically I have two models. Where a subject has many notes. class Subject < ActiveRecord::Base validates_presence_of :title has_many :notes end class Note < ActiveRecord::Base validates_presence_of :title belongs_to :subject end My routes.rb file nests these two resources as such: ActionController::Routing::Routes.draw do |map| map.resources :subjects, :has_many => :notes end The NotesController.rb file looks like this: class NotesController < ApplicationController # POST /notes # POST /notes.xml def create @subject = Subject.find(params[:subject_id]) @note = @subject.notes.create!(params[:note]) respond_to do |format| format.html { redirect_to(@subject) } end end end Finally this is my RSpec spec which should simply post my mocked objects to the NotesController and be executed... which it does: it "should create note and redirect to subject without javascript" do # usual rails controller test setup here subject = mock(Subject) Subject.stub(:find).and_return(subject) notes_proxy = mock('association proxy', { "create!" => Note.new }) subject.stub(:notes).and_return(notes_proxy) post :create, :subject_id => subject, :note => { :title => 'note title', :body => 'note body' } end The problem is that when the RSpec post method is called. The NotesController correctly handles the Mock Subject object, and create! the new Note object. However when the NoteController#Create method tries to redirect_to I get the following error: NoMethodError in 'NotesController should create note and redirect to subject without javascript' undefined method `spec_mocks_mock_url' for #<NotesController:0x1034495b8> Now this is caused by a bit of Rails trickery that passes an ActiveRecord object (@subject, in our case, which isn't ActiveRecord but a Mock object), eventually to url_for who passes all the options to the Rails' Routing, which then determines the URL. My question is how can I mock Subject so that the correct options are passed so that I my test passes. I've tried passing in :controller = 'subjects' options but no joy. Is there some other way of doing this? Thanks...

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• IoC/DI in the face of winforms and other generated code

  - by Kaleb Pederson

  When using dependency injection (DI) and inversion of control (IoC) objects will typically have a constructor that accepts the set of dependencies required for the object to function properly. For example, if I have a form that requires a service to populate a combo box you might see something like this: // my files public interface IDataService { IList<MyData> GetData(); } public interface IComboDataService { IList<MyComboData> GetComboData(); } public partial class PopulatedForm : BaseForm { private IDataService service; public PopulatedForm(IDataService service) { //... InitializeComponent(); } } This works fine at the top level, I just use my IoC container to resolve the dependencies: var form = ioc.Resolve<PopulatedForm>(); But in the face of generated code, this gets harder. In winforms a second file composing the rest of the partial class is generated. This file references other components, such as custom controls, and uses no-args constructors to create such controls: // generated file: PopulatedForm.Designer.cs public partial class PopulatedForm { private void InitializeComponent() { this.customComboBox = new UserCreatedComboBox(); // customComboBox has an IComboDataService dependency } } Since this is generated code, I can't pass in the dependencies and there's no easy way to have my IoC container automatically inject all the dependencies. One solution is to pass in the dependencies of each child component to PopulatedForm even though it may not need them directly, such as with the IComboDataService required by the UserCreatedComboBox. I then have the responsibility to make sure that the dependencies are provided through various properties or setter methods. Then, my PopulatedForm constructor might look as follows: public PopulatedForm(IDataService service, IComboDataService comboDataService) { this.service = service; InitializeComponent(); this.customComboBox.ComboDataService = comboDataService; } Another possible solution is to have the no-args constructor to do the necessary resolution: public class UserCreatedComboBox { private IComboDataService comboDataService; public UserCreatedComboBox() { if (!DesignMode && IoC.Instance != null) { comboDataService = Ioc.Instance.Resolve<IComboDataService>(); } } } Neither solution is particularly good. What patterns and alternatives are available to more capably handle dependency-injection in the face of generated code? I'd love to see both general solutions, such as patterns, and ones specific to C#, Winforms, and Autofac.

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• Silverlight ControlTemplate and F#

  - by akaphenom

  Has anybody had any success incorporating a Silverlight ControlTemplate into an F# Silverlight application. I am trying to add transitions to the Navgiation.Frame element and following along on with a C# example: http://www.davidpoll.com/2009/07/19/silverlight-3-navigation-adding-transitions-to-the-frame-control The downloaded source uses the MSBUILD:Compile option on the template XAML and the file is included as a "Page"... ILDASM doesn't show any object created for the XAML; In my project I incldued it as a "Resource" (same as I have done for my pages) and referenced it in app.xaml: <Application xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" x:Class="Module1.MyApp"> <Application.Resources> <ResourceDictionary> <ResourceDictionary.MergedDictionaries> <ResourceDictionary Source="/FSSilverlightApp;component/TransitioningFrame.xaml"/> </ResourceDictionary.MergedDictionaries> </ResourceDictionary> </Application.Resources> </Application> the TransitioningFrame.xaml is as follows: <ResourceDictionary xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:navigation="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Navigation" xmlns:toolkit="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Layout.Toolkit"> <ControlTemplate x:Key="TransitioningFrame" TargetType="navigation:Frame"> <Border Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}"> <toolkit:TransitioningContentControl Content="{TemplateBinding Content}" Cursor="{TemplateBinding Cursor}" Margin="{TemplateBinding Padding}" HorizontalAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalAlignment="{TemplateBinding VerticalContentAlignment}" HorizontalContentAlignment="{TemplateBinding HorizontalContentAlignment}" VerticalContentAlignment="{TemplateBinding VerticalContentAlignment}" Transition="DefaultTransition" /> </Border> </ControlTemplate> </ResourceDictionary> My page objects all load their respective xaml with the follwoing code: type Page1() as this = inherit UriUserControl("/FSSilverlightApp;component/Page1.xaml") do Application.LoadComponent(this, base.uri) and somewhere in app startup: let p1 = new Page1() I donot have a comparable piece for the ControlTemplate - though I was hoping the application object and App.xaml would pull it in magically (as an aside, the reliance on this magic has made setting up a 100% f# silverlight application rather tricky - as nearly all the published articles I find are based around wizards and short cuts - very little on the acual plumbing - ugh). Any advice or thougts on the subject are appreciated.

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• Facing Memory Leaks in AES Encryption Method.

  - by Mubashar Ahmad

  Can anyone please identify is there any possible memory leaks in following code. I have tried with .Net Memory Profiler and it says "CreateEncryptor" and some other functions are leaving unmanaged memory leaks as I have confirmed this using Performance Monitors. but there are already dispose, clear, close calls are placed wherever possible please advise me accordingly. its a been urgent. public static string Encrypt(string plainText, string key) { //Set up the encryption objects byte[] encryptedBytes = null; using (AesCryptoServiceProvider acsp = GetProvider(Encoding.UTF8.GetBytes(key))) { byte[] sourceBytes = Encoding.UTF8.GetBytes(plainText); using (ICryptoTransform ictE = acsp.CreateEncryptor()) { //Set up stream to contain the encryption using (MemoryStream msS = new MemoryStream()) { //Perform the encrpytion, storing output into the stream using (CryptoStream csS = new CryptoStream(msS, ictE, CryptoStreamMode.Write)) { csS.Write(sourceBytes, 0, sourceBytes.Length); csS.FlushFinalBlock(); //sourceBytes are now encrypted as an array of secure bytes encryptedBytes = msS.ToArray(); //.ToArray() is important, don't mess with the buffer csS.Close(); } msS.Close(); } } acsp.Clear(); } //return the encrypted bytes as a BASE64 encoded string return Convert.ToBase64String(encryptedBytes); } private static AesCryptoServiceProvider GetProvider(byte[] key) { AesCryptoServiceProvider result = new AesCryptoServiceProvider(); result.BlockSize = 128; result.KeySize = 256; result.Mode = CipherMode.CBC; result.Padding = PaddingMode.PKCS7; result.GenerateIV(); result.IV = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }; byte[] RealKey = GetKey(key, result); result.Key = RealKey; // result.IV = RealKey; return result; } private static byte[] GetKey(byte[] suggestedKey, SymmetricAlgorithm p) { byte[] kRaw = suggestedKey; List<byte> kList = new List<byte>(); for (int i = 0; i < p.LegalKeySizes[0].MaxSize; i += 8) { kList.Add(kRaw[(i / 8) % kRaw.Length]); } byte[] k = kList.ToArray(); return k; }

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• Confused as to how to validate spring mvc form, what are my options?

  - by Blankman

  Latest spring mvc, using freemarker. Hoping someone could tell me what my options are in terms of validating a form with spring mvc, and what the recommend way would be to do this. I have a form that doesn't map directly to a model, it has input fields that when posted, will be used to initialze 2 model objects which I will then need to validate, and if they pass I will save them. If they fail, I want to return back to the form, pre-fill the values with what the user entered and display the error messages. I have read here and there about 2 methods, once of which I have done and understand how it works: @RequestMapping(...., method = RequestMethod.POST) public ModelAndView myMethod(@Valid MyModel, BindingResult bindingResult) { ModelAndView mav = new ModelAndView("some/view"); mav.addObject("mymodel", myModel); if(bindingResult.hasErrors()) { return mav; } } Now this worked if my form mapped directly to the form, but in my situation I have: form fields that don't map to any specific model, they have a few properties from 2 models. before validation occurrs, I need to create the 2 models manually, set the values from the values from the form, and manually set some properties also: Call validate on both models (model1, model2), and append these error messages to the errors collection which I need to pass back to the same view page if things don't work. when the form posts, I have to do some database calls, and based on those results may need to add additional messages to the errors collection Can someone tell me how to do this sort of validation? Pseudo code below: Model1 model1 = new Model1(); Model2 model2 = new Model2(); // manually or somehow automatically set the posted form values to model1 and model2. // set some fields manually, not from posted form model1.setProperty10(GlobalSettings.getDefaultProperty10()); model2.setProperty11(GlobalSettings.getDefaultProperty11()); // db calls, if they fail, add to errors collection if(bindingResult.hasErrors()) { return mav; } // validation passed, save Model1Service.save(model1); Model2Service.save(model2); redirect to another view Update I have using the JSR 303 annotations on my models right now, and it would great if I can use those still. Update II Please read the bounty description below for a summary of what I am looking for.

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• Tomcat JNDI Connection Pool docs - Random Connection Closed Exceptions

  - by Andy Faibishenko

  I found this in the Tomcat documentation here What I don't understand is why they close all the JDBC objects twice - once in the try{} block and once in the finally{} block. Why not just close them once in the finally{} clause? This is the relevant docs: Random Connection Closed Exceptions These can occur when one request gets a db connection from the connection pool and closes it twice. When using a connection pool, closing the connection just returns it to the pool for reuse by another request, it doesn't close the connection. And Tomcat uses multiple threads to handle concurrent requests. Here is an example of the sequence of events which could cause this error in Tomcat: Request 1 running in Thread 1 gets a db connection. Request 1 closes the db connection. The JVM switches the running thread to Thread 2 Request 2 running in Thread 2 gets a db connection (the same db connection just closed by Request 1). The JVM switches the running thread back to Thread 1 Request 1 closes the db connection a second time in a finally block. The JVM switches the running thread back to Thread 2 Request 2 Thread 2 tries to use the db connection but fails because Request 1 closed it. Here is an example of properly written code to use a db connection obtained from a connection pool: Connection conn = null; Statement stmt = null; // Or PreparedStatement if needed ResultSet rs = null; try { conn = ... get connection from connection pool ... stmt = conn.createStatement("select ..."); rs = stmt.executeQuery(); ... iterate through the result set ... rs.close(); rs = null; stmt.close(); stmt = null; conn.close(); // Return to connection pool conn = null; // Make sure we don't close it twice } catch (SQLException e) { ... deal with errors ... } finally { // Always make sure result sets and statements are closed, // and the connection is returned to the pool if (rs != null) { try { rs.close(); } catch (SQLException e) { ; } rs = null; } if (stmt != null) { try { stmt.close(); } catch (SQLException e) { ; } stmt = null; } if (conn != null) { try { conn.close(); } catch (SQLException e) { ; } conn = null; } }

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• SHAREPOINT: Custom Field type property storage defined for custom field

  - by Eric Rockenbach

  ok here is a great question. I have a set of generic custom fields that are highly configurable from an end user perspective and the configuration is getting overbearing as there are nearly 100 plus items each custom field allows you to perform in the areas of Server/Client Validation, Server/Client Events/Actions, Server/Client Bindings parent/child, display properties for form/control, etc, etc. Right now I'm storing most of these values as "Text" in my field xml for my propertyschema. I'm very familiar with the multi column value, but this is not a complex custom type in sense it's an array. I also considered creating serilzable objects and stuffing them into the text field and then pulling out and de-serilizing them when editing through the field editor or acting on the rules through the custom spfield. So I'm trying to take the following for example <PropertySchema> <Fields> <Field Name="EntityColumnName" Hidden="TRUE" DisplayName="EntityColumnName" MaxLength="500" DisplaySize="200" Type="Text"> <default></default> </Field> <Field Name="EntityColumnParentPK" Hidden="TRUE" DisplayName="EntityColumnParentPK" MaxLength="500" DisplaySize="200" Type="Text"> <default></default> </Field> <Field Name="EntityColumnValueName" Hidden="TRUE" DisplayName="EntityColumnValueName" MaxLength="500" DisplaySize="200" Type="Text"> <default></default> </Field> <Field Name="EntityListName" Hidden="TRUE" DisplayName="EntityListName" MaxLength="500" DisplaySize="200" Type="Text"> <default></default> </Field> <Field Name="EntitySiteUrl" Hidden="TRUE" DisplayName="EntitySiteUrl" MaxLength="500" DisplaySize="200" Type="Text"> <default></default> </Field> </Fields> <PropertySchema> And turn it into this... <PropertySchema> <Fields> <Field Name="ServerValidationRules" Hidden="TRUE" DisplayName="ServerValidationRules" Type="ServerValidationRulesType"> <default></default> </Field> </Fields> <PropertySchema> Ideas?????

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• Unexpected behavior of IntentService

  - by kknight

  I used IntentService in my code instead of Service because IntentService creates a thread for me in onHandleIntent(Intent intent), so I don't have to create a Thead myself in the code of my service. I expected that two intents to the same IntentSerivce will execute in parallel because a thread is generated in IntentService for each invent. But my code turned out that the two intents executed in sequential way. This is my IntentService code: public class UpdateService extends IntentService { public static final String TAG = "HelloTestIntentService"; public UpdateService() { super("News UpdateService"); } protected void onHandleIntent(Intent intent) { String userAction = intent .getStringExtra("userAction"); Log.v(TAG, "" + new Date() + ", In onHandleIntent for userAction = " + userAction + ", thread id = " + Thread.currentThread().getId()); if ("1".equals(userAction)) { try { Thread.sleep(20 * 1000); } catch (InterruptedException e) { Log.e(TAG, "error", e); } Log.v(TAG, "" + new Date() + ", This thread is waked up."); } } } And the code call the service is below: public class HelloTest extends Activity { //@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Intent selectIntent = new Intent(this, UpdateService.class); selectIntent.putExtra("userAction", "1"); this.startService(selectIntent); selectIntent = new Intent(this, UpdateService.class); selectIntent.putExtra("userAction", "2"); this.startService(selectIntent); } } I saw this log message in the log: V/HelloTestIntentService( 848): Wed May 05 14:59:37 PDT 2010, In onHandleIntent for userAction = 1, thread id = 8 D/dalvikvm( 609): GC freed 941 objects / 55672 bytes in 99ms V/HelloTestIntentService( 848): Wed May 05 15:00:00 PDT 2010, This thread is waked up. V/HelloTestIntentService( 848): Wed May 05 15:00:00 PDT 2010, In onHandleIntent for userAction = 2, thread id = 8 I/ActivityManager( 568): Stopping service: com.example.android/.UpdateService The log shows that the second intent waited the first intent to finish and they are in the same thread. It there anything I misunderstood of IntentService. To make two service intents execute in parallel, do I have to replace IntentService with service and start a thread myself in the service code? Thanks.

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• Rails: Passing new child object placeholder (build) to parent view

  - by Meltemi

  I've got 2 classes of objects... Magician has_many Rabbits and Rabbit belongs_to Magician. When viewing a Magician (show.html) I'd like to list all the associated Rabbits and then have some blank fields with a submit button to add a new Rabbit. To do so I build a new rabbit (associated to the current magician) in the Magician's show method (below). Edit2: found way to make it work but not sure if it's the "Rails way"? see comments inline (below): If I build the rabbit in Magician's show method then when show is rendered an empty (and invalid) rabbit ends the list before the new rabbit form fields are then shown. If I build it in the view itself then everything works & renders correctly. I was led to believe that we should not be doing this type of stuff in the view...if so, what's the proper way to address this? #/app/controllers/magicians_controller.rb class MagiciansController < ApplicationController respond_to :html, :json def show @magician = Magician.find(params[:id]) @rabbit = @magician.rabbits.build # <=== build here and empty rabbit gets # included in @magician.rabbits when they're rendered... # but is NOT included in @magician.rabbits.count for some reason?!?!? respond_with(@magician) end ... end #view/magicians/show.html.haml %p %b Name: = @magician.name %h2 Rabbits = "There are #{pluralize(@magician.rabbits.count, "rabbit")}" = render @magician.rabbits, :target => @magician %h2 Add a rabbit: - @rabbit = @clown.rabbits.build -# <=== build here and everything SEEMS to work = render :partial =>"rabbits/form", :locals => { :parent => @magician, :foreign_key => :magician_id, :flash => flash } Edit1: Adding generated html from partial as per request: <p> <b>Rabbit:</b> <b>Color:</b> | <b>ID:</b> <a href="/magicians/2/rabbits" data-confirm="Sure? A bunny will die" data-method="delete" rel="nofollow">Kill Rabbit</a> </p> And I suppose you probably want to see the partial that generates this: %p %b Rabbit: = rabbit.name %b Color: = rabbit.color | %b ID: = rabbit.id = link_to("Kill Rabbit", [target, rabbit], :method => :delete, :confirm => "Sure? A bunny will die")

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• TcpListener is queuing connections faster than I can clear them

  - by Matthew Brindley

  As I understand it, TcpListener will queue connections once you call Start(). Each time you call AcceptTcpClient (or BeginAcceptTcpClient), it will dequeue one item from the queue. If we load test our TcpListener app by sending 1,000 connections to it at once, the queue builds far faster than we can clear it, leading (eventually) to timeouts from the client because it didn't get a response because its connection was still in the queue. However, the server doesn't appear to be under much pressure, our app isn't consuming much CPU time and the other monitored resources on the machine aren't breaking a sweat. It feels like we're not running efficiently enough right now. We're calling BeginAcceptTcpListener and then immediately handing over to a ThreadPool thread to actually do the work, then calling BeginAcceptTcpClient again. The work involved doesn't seem to put any pressure on the machine, it's basically just a 3 second sleep followed by a dictionary lookup and then a 100 byte write to the TcpClient's stream. Here's the TcpListener code we're using: // Thread signal. private static ManualResetEvent tcpClientConnected = new ManualResetEvent(false); public void DoBeginAcceptTcpClient(TcpListener listener) { // Set the event to nonsignaled state. tcpClientConnected.Reset(); listener.BeginAcceptTcpClient( new AsyncCallback(DoAcceptTcpClientCallback), listener); // Wait for signal tcpClientConnected.WaitOne(); } public void DoAcceptTcpClientCallback(IAsyncResult ar) { // Get the listener that handles the client request, and the TcpClient TcpListener listener = (TcpListener)ar.AsyncState; TcpClient client = listener.EndAcceptTcpClient(ar); if (inProduction) ThreadPool.QueueUserWorkItem(state => HandleTcpRequest(client, serverCertificate)); // With SSL else ThreadPool.QueueUserWorkItem(state => HandleTcpRequest(client)); // Without SSL // Signal the calling thread to continue. tcpClientConnected.Set(); } public void Start() { currentHandledRequests = 0; tcpListener = new TcpListener(IPAddress.Any, 10000); try { tcpListener.Start(); while (true) DoBeginAcceptTcpClient(tcpListener); } catch (SocketException) { // The TcpListener is shutting down, exit gracefully CheckBuffer(); return; } } I'm assuming the answer will be related to using Sockets instead of TcpListener, or at least using TcpListener.AcceptSocket, but I wondered how we'd go about doing that? One idea we had was to call AcceptTcpClient and immediately Enqueue the TcpClient into one of multiple Queue<TcpClient> objects. That way, we could poll those queues on separate threads (one queue per thread), without running into monitors that might block the thread while waiting for other Dequeue operations. Each queue thread could then use ThreadPool.QueueUserWorkItem to have the work done in a ThreadPool thread and then move onto dequeuing the next TcpClient in its queue. Would you recommend this approach, or is our problem that we're using TcpListener and no amount of rapid dequeueing is going to fix that?

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• Activate a (COM Interop based) ActiveX contol using registration free com

  - by embnut

  I have a (COM Interop based) ActiveX contol that I am trying to use with registration free com. When the control loads the control is inactive (does not responds to events, control not fully rendered etc). After much search I discovered that COM objects using reg-free-com use the miscStatus attribute to set the initial state to get correctly activated. I know how to use it with a comClass which corresponds to a native COM Object. 1) What is the equivalent of the following for clrClass element which corresponds to a COM-interop object? <comClass clsid="{qqqqqqqq-wwww-eeee-rrrr-00C0F0283628}" tlbid="{xxxxxxxx-yyyy-zzzz-aaaa-0000F8754DA1}" threadingModel="Both" progid="SomeCompany.SomeOleControl" description="Some ActiveX Control" miscStatus="recomposeonresize,insideout,activatewhenvisible,nouiactivate" > 2) The COM client I am using is Visual FoxPro. If the (1) is not possible what can I do in VFP to activate the inactive ActiveX control. (I dont mind VB or C# input too if I can use it to find the equivalent foxpro) Currently I tried the following this.AddObject('OleControl1', 'oleControl', 'SomeCompany.SomeOleControl') this.OleControl1.AutoActivate = 3 this.OleControl1.Visible = .T. this.OleControl1.SetFocus But I the OleControl1 gets focus before passing events like mouse click to its subelements. So I have to click twice on it to do the necessary action, any time it does not have focus. I would like the control to act as if the "nouiactivate" of the miscStatus value is set. 3) Is there any other way of accomplishing what I want to do? Hans Passant, here is the listing of current Assembly.dll.manifest. The formatting in the comment made it unreadable. <?xml version="1.0" encoding="UTF-8" standalone="yes"?> <assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0"> <assemblyIdentity name="Assembly" version="1.0.0.0" type="win32" publicKeyToken="wwwwwwwwwwwwwwww"/> <clrClass name="SomeCompany.SomeOleControl" clsid="{qqqqqqqq-wwww-eeee-rrrr-00C0F0283628}" progid="SomeCompany.SomeOleControl" threadingModel="Both"/> <file name="Assembly.tlb"> <typelib tlbid="{xxxxxxxx-yyyy-zzzz-aaaa-0000F8754DA1}" version="1.0" helpdir="" flags="hasdiskimage"/> </file> </assembly>

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• F# Equivalent to Enumerable.OfType<'a>

  - by Joel Mueller

  ...or, how do I filter a sequence of classes by the interfaces they implement? Let's say I have a sequence of objects that inherit from Foo, a seq<#Foo>. In other words, my sequence will contain one or more of four different subclasses of Foo. Each subclass implements a different independent interface that shares nothing with the interfaces implemented by the other subclasses. Now I need to filter this sequence down to only the items that implement a particular interface. The C# version is simple: void MergeFoosIntoList<T>(IEnumerable<Foo> allFoos, IList<T> dest) where T : class { foreach (var foo in allFoos) { var castFoo = foo as T; if (castFoo != null) { dest.Add(castFoo); } } } I could use LINQ from F#: let mergeFoosIntoList (foos:seq<#Foo>) (dest:IList<'a>) = System.Linq.Enumerable.OfType<'a>(foos) |> Seq.iter dest.Add However, I feel like there should be a more idiomatic way to accomplish it. I thought this would work... let mergeFoosIntoList (foos:seq<#Foo>) (dest:IList<'a>) = foos |> Seq.choose (function | :? 'a as x -> Some(x) | _ -> None) |> Seq.iter dest.Add However, the complier complains about :? 'a - telling me: This runtime coercion or type test from type 'b to 'a involves an indeterminate type based on information prior to this program point. Runtime type tests are not allowed on some types. Further type annotations are needed. I can't figure out what further type annotations to add. There's no relationship between the interface 'a and #Foo except that one or more subclasses of Foo implement that interface. Also, there's no relationship between the different interfaces that can be passed in as 'a except that they are all implemented by subclasses of Foo. I eagerly anticipate smacking myself in the head as soon as one of you kind people points out the obvious thing I've been missing.

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• How is IObservable<double>.Average supposed to work?

  - by Dan Tao

  Update Looks like Jon Skeet was right (big surprise!) and the issue was with my assumption about the Average extension providing a continuous average (it doesn't). For the behavior I'm after, I wrote a simple ContinuousAverage extension method, the implementation of which I am including here for the benefit of others who may want something similar: public static class ObservableExtensions { private class ContinuousAverager { private double _mean; private long _count; public ContinuousAverager() { _mean = 0.0; _count = 0L; } // undecided whether this method needs to be made thread-safe or not // seems that ought to be the responsibility of the IObservable (?) public double Add(double value) { double delta = value - _mean; _mean += (delta / (double)(++_count)); return _mean; } } public static IObservable<double> ContinousAverage(this IObservable<double> source) { var averager = new ContinuousAverager(); return source.Select(x => averager.Add(x)); } } I'm thinking of going ahead and doing something like the above for the other obvious candidates as well -- so, ContinuousCount, ContinuousSum, ContinuousMin, ContinuousMax ... perhaps ContinuousVariance and ContinuousStandardDeviation as well? Any thoughts on that? Original Question I use Rx Extensions a little bit here and there, and feel I've got the basic ideas down. Now here's something odd: I was under the impression that if I wrote this: var ticks = Observable.FromEvent<QuoteEventArgs>(MarketDataProvider, "MarketTick"); var bids = ticks .Where(e => e.EventArgs.Quote.HasBid) .Select(e => e.EventArgs.Quote.Bid); var bidsSubscription = bids.Subscribe( b => Console.WriteLine("Bid: {0}", b) ); var avgOfBids = bids.Average(); var avgOfBidsSubscription = avgOfBids.Subscribe( b => Console.WriteLine("Avg Bid: {0}", b) ); I would get two IObservable<double> objects (bids and avgOfBids); one would basically be a stream of all the market bids from my MarketDataProvider, the other would be a stream of the average of these bids. So something like this: Bid Avg Bid 1 1 2 1.5 1 1.33 2 1.5 It seems that my avgOfBids object isn't doing anything. What am I missing? I think I've probably misunderstood what Average is actually supposed to do. (This also seems to be the case for all of the aggregate-like extension methods on IObservable<T> -- e.g., Max, Count, etc.)

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• Create links programmatically inside an EmberJS view

  - by Michael Gallego

  I have a pretty complex view to render which involves some kind of recursion (the typical folder/file nested list). The fact that it contains heterogeneous objects (folders and files) make it even harder to write Handlebars templates. Therefore, the only solution I've found is to create a view, and manually fill the render buffer. I came with the following solution: App.LibraryContentList = Ember.View.extend({ tagName: 'ol', classNames: ['project-list', 'dd-list'], nameChanged: function() { this.rerender(); }.observes('[email protected]'), render: function(buffer) { // We only start with depth of zero var content = this.get('content').filterProperty('depth', 0); content.forEach(function(item) { this.renderItem(buffer, item); }, this); }, renderItem: function(buffer, item) { switch (item.constructor.toString()) { case 'Photo.Folder': this.renderFolder(buffer, item); break; case 'Photo.File': this.renderFile(buffer, item); break; } }, renderFolder: function(buffer, folder) { buffer.push('<li class="folder dd-item">'); buffer.push('<span class="dd-handle">' + folder.get('name') + '</span>'); // Merge sub folders and files, and sort them by sort order var content = this.mergeAndSort(); if (content.get('length') > 0) { buffer.push('<ol>'); content.forEach(function(item) { this.renderItem(buffer, item); }, this); buffer.push('</ol>'); } buffer.push('</li>'); }, renderFile: function(buffer, album) { buffer.push('<li class="album dd-item">'); buffer.push('<span class="dd-handle">' + file.get('name') + '</span>'); buffer.push('</li>'); } }); Now, what I'd like is to be able to add links so that each folder and each file is clickable and redirect to another route. But how am I supposed to do that, as I don't have access to the linkTo helper? I've tried to play with the LinkView view, but without any success. Should I register handlers manually for each item? I've also thought about breaking that with a CollectionView instead, and splitting the content by depth so that I could render it using templates, but it seems more complicated. Any thoughts?

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• Implementing INotifyPropertyChanged with PostSharp 1.5

  - by no9

  Hello all. Im new to .NET and WPF so i hope i will ask the question correctly. I am using INotifyPropertyChanged implemented using PostSharp 1.5: [Serializable, DebuggerNonUserCode, AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Class, AllowMultiple = false, Inherited = false), MulticastAttributeUsage(MulticastTargets.Class, AllowMultiple = false, Inheritance = MulticastInheritance.None, AllowExternalAssemblies = true)] public sealed class NotifyPropertyChangedAttribute : CompoundAspect { public int AspectPriority { get; set; } public override void ProvideAspects(object element, LaosReflectionAspectCollection collection) { Type targetType = (Type)element; collection.AddAspect(targetType, new PropertyChangedAspect { AspectPriority = AspectPriority }); foreach (var info in targetType.GetProperties(BindingFlags.Public | BindingFlags.Instance).Where(pi => pi.GetSetMethod() != null)) { collection.AddAspect(info.GetSetMethod(), new NotifyPropertyChangedAspect(info.Name) { AspectPriority = AspectPriority }); } } } [Serializable] internal sealed class PropertyChangedAspect : CompositionAspect { public override object CreateImplementationObject(InstanceBoundLaosEventArgs eventArgs) { return new PropertyChangedImpl(eventArgs.Instance); } public override Type GetPublicInterface(Type containerType) { return typeof(INotifyPropertyChanged); } public override CompositionAspectOptions GetOptions() { return CompositionAspectOptions.GenerateImplementationAccessor; } } [Serializable] internal sealed class NotifyPropertyChangedAspect : OnMethodBoundaryAspect { private readonly string _propertyName; public NotifyPropertyChangedAspect(string propertyName) { if (string.IsNullOrEmpty(propertyName)) throw new ArgumentNullException("propertyName"); _propertyName = propertyName; } public override void OnEntry(MethodExecutionEventArgs eventArgs) { var targetType = eventArgs.Instance.GetType(); var setSetMethod = targetType.GetProperty(_propertyName); if (setSetMethod == null) throw new AccessViolationException(); var oldValue = setSetMethod.GetValue(eventArgs.Instance, null); var newValue = eventArgs.GetReadOnlyArgumentArray()[0]; if (oldValue == newValue) eventArgs.FlowBehavior = FlowBehavior.Return; } public override void OnSuccess(MethodExecutionEventArgs eventArgs) { var instance = eventArgs.Instance as IComposed<INotifyPropertyChanged>; var imp = instance.GetImplementation(eventArgs.InstanceCredentials) as PropertyChangedImpl; imp.OnPropertyChanged(_propertyName); } } [Serializable] internal sealed class PropertyChangedImpl : INotifyPropertyChanged { private readonly object _instance; public PropertyChangedImpl(object instance) { if (instance == null) throw new ArgumentNullException("instance"); _instance = instance; } public event PropertyChangedEventHandler PropertyChanged; internal void OnPropertyChanged(string propertyName) { if (string.IsNullOrEmpty(propertyName)) throw new ArgumentNullException("propertyName"); var handler = PropertyChanged as PropertyChangedEventHandler; if (handler != null) handler(_instance, new PropertyChangedEventArgs(propertyName)); } } } Then i have a couple of classes (user and adress) that implement [NotifyPropertyChanged]. It works fine. But what i want would be that if the child object changes (in my example address) that the parent object gets notified (in my case user). Would it be possible to expand this code so it automaticly creates listeners on parent objects that listen for changes in its child objets?

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• Uses of a C++ Arithmetic Promotion Header

  - by OlduvaiHand

  I've been playing around with a set of templates for determining the correct promotion type given two primitive types in C++. The idea is that if you define a custom numeric template, you could use these to determine the return type of, say, the operator+ function based on the class passed to the templates. For example: // Custom numeric class template <class T> struct Complex { Complex(T real, T imag) : r(real), i(imag) {} T r, i; // Other implementation stuff }; // Generic arithmetic promotion template template <class T, class U> struct ArithmeticPromotion { typedef typename X type; // I realize this is incorrect, but the point is it would // figure out what X would be via trait testing, etc }; // Specialization of arithmetic promotion template template <> class ArithmeticPromotion<long long, unsigned long> { typedef typename unsigned long long type; } // Arithmetic promotion template actually being used template <class T, class U> Complex<typename ArithmeticPromotion<T, U>::type> operator+ (Complex<T>& lhs, Complex<U>& rhs) { return Complex<typename ArithmeticPromotion<T, U>::type>(lhs.r + rhs.r, lhs.i + rhs.i); } If you use these promotion templates, you can more or less treat your user defined types as if they're primitives with the same promotion rules being applied to them. So, I guess the question I have is would this be something that could be useful? And if so, what sorts of common tasks would you want templated out for ease of use? I'm working on the assumption that just having the promotion templates alone would be insufficient for practical adoption. Incidentally, Boost has something similar in its math/tools/promotion header, but it's really more for getting values ready to be passed to the standard C math functions (that expect either 2 ints or 2 doubles) and bypasses all of the integral types. Is something that simple preferable to having complete control over how your objects are being converted? TL;DR: What sorts of helper templates would you expect to find in an arithmetic promotion header beyond the machinery that does the promotion itself?

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