object relationships - Page 517

How are value types implemented in .NET

- by Michael

Been looking around the net and can't find any articles about how value types are actually implemented. For instance, an Int32 is a struct and it's direct parent is System.ValueType and that's ultimate parent is System.Object. Object is a class - I imagine ValueType is a class? What's the class hierarchy? What part does the CLR have to play? At what stage and how does the CLR know to allocate value types to the stack? (FYI, I am aware that value types are stored where they are declared).

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Is it safe to unset PHP super-globals if this behavior is documented?

- by Stephen

I'm building a PHP framework, and in it I have a request object that parses the url as well as the $_GET, $_POST and $_FILE superglobals. I want to encourage safe web habits, so I'm protecting the data against SQL injection, etc. In order to ensure users of this framework are accessing the safe, clean data through the request object, I plan to use unset($_GET, $_POST, $_REQUEST); after parsing those variables. I will document this in the method comments, and explain in the framework documentation that this is happening. My question is: Would this be desirable behavior? What are the potential pitfalls that I have not foreseen?

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Browser not handling exception from AJAX panel, ASP.NET c#

- by Grant

Hi, i am having trouble catching errors in an AJAX panel. Even when i throw an exception in the c# code behind the front end completely ignores it. Here is the code i have setup, can anyone see why? I ideally want to show a js alert window on error. Code Behind: protected void btnX_Click(object sender, EventArgs e) { throw new ApplicationException("test"); } protected void ScriptManager_AsyncPostBackError(object sender, AsyncPostBackErrorEventArgs e) { ScriptManager.AsyncPostBackErrorMessage = e.Exception.Message; } Markup: <script type="text/javascript" language="javascript"> Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler); function EndRequestHandler(sender, e) { window.alert(e.get_error().name); } </script> <asp:ScriptManager ID="ScriptManager" runat="server" AllowCustomErrorsRedirect="true" OnAsyncPostBackError="ScriptManager_AsyncPostBackError" />

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Java: Reflection against casting when you know superclass

- by Ema

I don't know exactly how to define my doubt so please be patient if the question has already been asked. Let's say I have to dinamically instantiate an object. This object will surely be instance of a subclass of a known, immutable class A. I can obtain dinamically the specific implementation class. Would it be better to use reflection exactly as if I didn't know anything about the target class, or would it be preferrable/possible to do something like: A obj = (Class.forName("com.package.Sub-A")) new A(); where Sub-A extends A ? The purpose would be to avoid reflection overhead times... Thank you in advance.

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Is It Safe to Cast Away volatile?

- by Yan Cheng CHEOK

Most of the time, I am doing this way. class a { public: ~ a() { i = 100; // OK delete (int *)j; // Compiler happy. But, is it safe? // Error : delete j; } private: volatile int i; volatile int *j; }; int main() { a aa; } However, I saw an article here: https://www.securecoding.cert.org/confluence/display/seccode/EXP32-C.+Do+not+access+a+volatile+object+through+a+non-volatile+reference Casting away volatile allows access to an object through a non-volatile reference. This can result in undefined and perhaps unintended program behavior. So, what will be the workaround for my above code example?

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Pass parameter from page to ActiveX

- by nCdy

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Java template classes using generator or similar?

- by Hugh Perkins

Is there some library or generator that I can use to generate multiple templated java classes from a single template? Obviously Java does have a generics implementation itself, but since it uses type-erasure, there are lots of situations where it is less than adequate. For example, if I want to make a self-growing array like this: class EasyArray { T[] backingarray; } (where T is a primitive type), then this isn't possible. This is true for anything which needs an array, for example high-performance templated matrix and vector classes. It should probably be possible to write a code generator which takes a templated class and generates multiple instantiations, for different types, eg for 'double' and 'float' and 'int' and 'String'. Is there something that already exists that does this? Edit: note that using an array of Object is not what I'm looking for, since it's no longer an array of primitives. An array of primitives is very fast, and uses only as much space a sizeof(primitive) * length-of-array. An array of object is an array of pointers/references, that points to Double objects, or similar, which could be scattered all over the place in memory, require garbage collection, allocation, and imply a double-indirection for access. Edit2: good god, voted down for asking for something that probably doesn't currently exist, but is technically possible and feasible? Does that mean that people looking for ways to improve things have already left the java community? Edit3: Here is code to show the difference in performance between primitive and boxed arrays: int N = 10*1000*1000; double[]primArray = new double[N]; for( int i = 0; i < N; i++ ) { primArray[i] = 123.0; } Object[] objArray = new Double[N]; for( int i = 0; i < N; i++ ) { objArray[i] = 123.0; } tic(); primArray = new double[N]; for( int i = 0; i < N; i++ ) { primArray[i] = 123.0; } toc(); tic(); objArray = new Double[N]; for( int i = 0; i < N; i++ ) { objArray[i] = 123.0; } toc(); Results: double[] array: 148 ms Double[] array: 4614 ms Not even close!

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VB6 debugging- doesn't go to error handling code.

- by Can Ho

Hi, I'm maintaining a vb6 project(ActiveX DLL). When debugging, the app run into the following function: Public Function HasValue(ByVal vValue) As Boolean On Error GoTo Err If IsMissing(vValue) Then HasValue = False ElseIf IsNull(vValue) Or Len(vValue) = 0 Then HasValue = False ElseIf isEmpty(vValue) Then HasValue = False Else HasValue = True End If Exit Function Err: If IsArray(vValue) Or IsObject(vValue) Then HasValue = True Else HasValue = False End If End Function and it stops at the line ElseIf IsNull(vValue) Or Len(vValue) = 0 Then vValue is a custom object, contains some properties(obviously, not null). Although I didn't put any break point there, the app stopped there and alerted error dialog saying that "Run-time error '438': Object doesn't support this property or method". We had error handling code but the app didn't run to error handling code. It just stopped at the line causing the error and I had to stop the application. Do you have any idea about that? Thank you very much.

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How to create an image from canvas data?

- by Jakub Hampl

In my application I am trying to save an arbitrary part of a rendered HTML canvas to an image file. In my Javascript I call ctx.getImageData(x, y, w, h) and pass the resulting object to my macruby code (though if you know a solution in objc I am also very interested). There I'm trying to create a NSBitmapImageRep object so that I can then save to an image format the user desires. This is my code so far (the function gets a WebScriptObject as it's argument): def setimagedata(d) w = d.valueForKey("width").to_i h = d.valueForKey("height").to_i data = Pointer.new(:char, d.valueForKey("data").valueForKey("length").to_i) d.valueForKey("data").valueForKey("length").to_i.times do |i| data[i] = d.valueForKey("data").webScriptValueAtIndex(i).to_i end puts "data complete" # get's called @exported_image = NSBitmapImageRep.alloc.initWithBitmapDataPlanes(data, pixelsWide: w, pixelsHigh:h, bitsPerSample: 32, samplesPerPixel: 4, hasAlpha: true, isPlanar: false, colorSpaceName: NSCalibratedRGBColorSpace, bitmapFormat: NSAlphaNonpremultipliedBitmapFormat, bytesPerRow: 0, bitsPerPixel: 0) puts "done" # doesn't get called end The code doesn't seem to get through the initWithBitmapDataPlanes function but gives no error. My question is: what am I doing wrong? Is this approach reasonable (if not, what would be better?).

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Data persistance with BufferedReader and PrintWriter?

- by Nazgulled

I have this simple application with a couple of classes which are all related. There's one, the main one, for which there is only one instance of. I need to save save and load that using a text stream. My instructor requirement is BufferedReader to load the stream and PrintWriter to save it. But is this even possible? To persist a data object/class with a text stream? I know how to do it with and object, using serialization. But I don't see how am I supposed to do it using text streams. Suggestions?

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C# Event routing in code behind

- by Nate

I'm building a WPF MVVM-ish application. I want to be able to display an event log containing items in a collection that exists in my viewmodel. I want any of the objects in the model to be able to add data to the event log. Therefore every object needs to be able to pass data back to one central collection for databinding in the view. I could implement an event in every one of my data classes and manually pass the events up the object heirarchy but this seems super clumsy. On the visual tree a Routed Event would take care of this, is there some equivelent in the model scope? Any other ideas?

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How to add Items to GridView in C# Windows Store App (Win8)

- by flexage

To keep things simple let's just say I have a c# Windows Store Project for Windows 8 that has the following items: GridView (PlatformsGrid) List«PlatformSearchResult» (allPlatforms) DataTemplate (PlatformDataTemplate) in standardstyles.xaml allPlatforms is a collection of "PlatformSearchResult"objects populated from an online API, and has the following 3 properties: ID Name Alias I am able to add a new item to the gridview for each object that exists in my allPlatforms collection, however the items are blank and do not show the data from my objects. A quick summary of the current code looks like this: XAML Markup:  <GridView x:Name="PlatformsGrid" Grid.Row="1" CanReorderItems="True" CanDragItems="True" ItemTemplate="{StaticResource PlatformDataTemplate}" > <GridView.ItemsPanel> <ItemsPanelTemplate> <WrapGrid MaximumRowsOrColumns="2" VerticalChildrenAlignment="Top" HorizontalChildrenAlignment="Center" /> </ItemsPanelTemplate> </GridView.ItemsPanel> </GridView> Data Template  <DataTemplate x:Key="PlatformDataTemplate"> <Grid Background="#FF939598" Height="250" Width="250"> <Image Source="/SampleImage.png" Stretch="UniformToFill"/> <StackPanel Orientation="Vertical" Background="#CC000000" Height="90" VerticalAlignment="Bottom"> <TextBlock Text="{Binding Name}" Margin="10,3,0,0" Width="242" Height="62" TextTrimming="WordEllipsis" TextWrapping="Wrap" HorizontalAlignment="Left"/> <TextBlock Text="{Binding Alias}" Margin="10,2,0,0" Width="186" Height="14" TextTrimming="WordEllipsis" HorizontalAlignment="Left" FontSize="9" Opacity="0.49"/> </StackPanel> </Grid> </DataTemplate> Controlling Function private async void FetchItemInfo_Loaded(object sender, RoutedEventArgs e) { // Get List of Top Games List<PlatformSearchResult> allPlatforms = new List<PlatformSearchResult>(); allPlatforms = await GamesDB.GetPlatforms(); // Dynamically Create Platform Tiles foreach (PlatformSearchResult platform in allPlatforms) { PlatformsGrid.DataContext = platform; PlatformsGrid.Items.Add(platform); } } How do I get the added items to show the appropriate object properties (ignoring the image for now), I'm just interested in populating the content of the TextBlocks. I appreciate any help anyone can provide! Thanks, Alex.

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Can I have fixed typed ArrayList in C#, just like C++?

- by Kazoom

I have an ArrayList which contains fixed type of objects. However everytime I need to extract an object a particular index, I need to typecast it to my user defined type from object type. Is there a way in C# to declare ArrayList of fixed types just like Java and C++, or is there a work around to avoid the typecasting everytime? Edit: I apologize I forgot mentioning that I require the datastructure to be thread-safe, which List is not. Otherwise I would have just used a normal Array. But I want to save myself from the effort of explicitly locking and unlocking while writing the array. So I thought of using ArrayList, synchronize it, but it requires typecasting every time.

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Can I use Cassandra to store objects?

- by Sandeep

Hi, My application works like this. A database(Mysql) where there is a command. The command is an object(consists of fields many fields like ints ans strings). There is a webservice which interact with the database and get the command from the db and performs some operation. The way how I am storing the command into db is by stripping all the fields and inserting them in to the db. Can I use cassandra in place of mysql and store the command object?

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Does this simple cache class need thread synchronization?

- by DayOne

Does this simple cache class need thread synchronization ... if I remove the lock _syncLock statement will encounter any problems? I think i can remove the locks as the references should be updated correctly right? ... BUt i'm think whar happens if client code is iterating over the GetMyDataStructure method and it get replaced? Thanks! public sealed class Cache { private readonly object _syncLock = new object(); private IDictionary<int, MyDataStructure> _cache; public Cache() { Refresh(); } public void Refresh() { lock (_syncLock) { _cache = DAL.GetMyDataStructure(); } } public IDictionary<int, MyDataStructure> **GetMyDataStructure**() { lock (_syncLock) { return _cache; } } }

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Powershell - remote folder availability while counting files

- by ziklop

I´m trying to make a Powershell script that reports if there´s a file older than x minutes on remote folder. I make this: $strfolder = 'folder1 ..................' $pocet = (Get-ChildItem \\server1\edi1\folder1\*.* ) | where-object {($_.LastWriteTime -lt (Get-Date).AddDays(-0).AddHours(-0).AddMinutes(-20))} | Measure-Object if($pocet.count -eq 0){Write-Host $strfolder "OK" -foreground Green} else {Write-Host $strfolder "ERROR" -foreground Red} But there´s one huge problem. The folder is often unavailable for me bacause of the high load and I found out when there is no connection it doesn´t report an error but continues with zero in $pocet.count. It means it reports everything is ok when the folder is unavailable. I was thinking about using if(Test-Path..) but what about it became unavailable just after passing Test-Path? Does anyone has a solution please? Thank you in advance

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Form graphics not set when form loads

- by Jimmy

My form has a group box which contains two overlapping rectangles. The form's other controls are two sets of four numeric up down controls to set the rectangles' colors. (nudF1,2,3 and 4 set the rectangle that's in front, and nudB1,2,3 and 4 set the rectangle that's behind.) Everything works fine, except that the rectangles do not display the colors set in the numeric up downs when the form first loads. The numeric up down controls' ChangeValue events all call the ShowColors() method. The form's Load event calls the csColorsForm_Load() method. Any suggestions? namespace csColors { public partial class csColorsForm : Form { public csColorsForm() { InitializeComponent(); } private void csColorsForm_Load(object sender, EventArgs e) { this.BackColor = System.Drawing.Color.DarkBlue; SetColors(sender, e); } private void SetColors(object sender, EventArgs e) { Control control = (Control)sender; String ctrlName = control.Name; Graphics objGraphics; Rectangle rect1, rect2; int colorBack, colorFore; objGraphics = this.grpColor.CreateGraphics(); // If calling control is not a forecolor control, paint backcolor rectangle if (ctrlName.Substring(0,4)!="nudF") { colorBack = int.Parse(SetColorsB("nudB"), NumberStyles.HexNumber); SolidBrush BrushB = new SolidBrush(Color.FromArgb(colorBack)); rect1 = new Rectangle(this.grpColor.Left, this.grpColor.Top, this.grpColor.Width, this.grpColor.Height); objGraphics.FillRectangle(BrushB, rect1); } // Always paint forecolor rectangle colorFore = int.Parse(SetColorsB("nudF"), NumberStyles.HexNumber); SolidBrush BrushF = new SolidBrush(Color.FromArgb(colorFore)); rect2 = new Rectangle(this.grpColor.Left, this.grpColor.Top, this.grpColor.Width, this.grpColor.Height); objGraphics.FillRectangle(BrushF, rect2); objGraphics.Dispose(); } private string SetColorsB(string nam) { string txt=""; for (int n = 1; n <= 4; ++n) { var ud = Controls[nam + n] as NumericUpDown; int hex = (int)ud.Value; txt += hex.ToString("X2"); } return txt; } private void btnClose_Click(object sender, EventArgs e) { this.Close(); } } }

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Where do I put the Current user query so as to not repeat per controller?

- by Kevin

I have a standard query that gets the current user object: @user = User.find_by_email(session[:email]) but I'm putting it as the first line in every single controller action which is obviously not the best way to do this. What is the best way to refactor this? Do I put this as a method in the Application controller (and if so, can you just show me a quick example)? Do I put the entire @user object into the session (has about 50 columns and some sensitive ones like is_admin)? Or is there another way to remove this kind of redundancy?

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Using locks inside a loop

- by Xaqron

// Member Variable private readonly object _syncLock = new object(); // Now inside a static method foreach (var lazyObject in plugins) { if ((string)lazyObject.Metadata["key"] = "something") { lock (_syncLock) { if (!lazyObject.IsValueCreated) lazyObject.value.DoSomething(); } return lazyObject.value; } } Here I need synchronized access per loop. There are many threads iterating this loop and based on the key they are looking for, a lazy instance is created and returned. lazyObject should not be created more that one time. Although Lazy class is for doing so and despite of the used lock, under high threading I have more than one instance created (I track this with a Interlocked.Increment on a volatile shared int and log it somewhere). The problem is I don't have access to definition of Lazy and MEF defines how the Lazy class create objects. My questions: 1) Why the lock doesn't work ? 2) Should I use an array of locks instead of one lock for performance improvement ?

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problem-configure-jboss-to-work-with-jndi(3)

- by Spiderman

Sorry for opening new thread every time for the same problem. It's just that I'd like to refine my question during my investigation and it's hard to do it in stackoverflow structure on the same question (maybe on purpose). Anyway, in continuation to this thread http://stackoverflow.com/questions/2843218/problem-configure-jboss-to-work-with-jndi2 I discovered that when running an application that is deployed on my JBoss 4.2.3.GA, when I perform: Context initialContext = new InitialContext(); Object dataSource = initialContext.lookup("java:/DefaultDS"); I get null as a return value even though DefaultDS is the default datasource that comes with Jboss installation. and generally, how come initialContext return null value? if the datasource is not found it should throw NamingException and in other case it should return real object. What can I do with null? isn't it a bad error handling of javax.naming.InitialContext ???

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What jQuery is triggered when a user selects a "drop down list" option

- by Ankur

I want to display a different form for different selections of this drop down list: <label> <select name="type" id="type"> <option value="object" selected="selected">Object</option> <option value="number">Number</option> <option value="text">Text</option> <option value="date">Date</option> <option value="time">Time</option> <option value="geo">Geospatial</option> <option value="currency">Currency</option> </select> </label> What would be the jQuery event that is triggered when a user selects one of these options. Would the .click() event be triggered in this case as well?

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Lifetime of implicitly casted temporaries

- by Answeror

I have seen this question. It seems that regardless of the cast, the temporary object(s) will "survive" until the fullexpression evaluated. But in the following scenario: void foo(boost::tuple<const double&> n) { printf("%lf\n", n.get<0>()); } int main() { foo(boost::tuple<const double&>(2));//#1 foo(boost::make_tuple(2));//#2 return 0; } 1 run well, but 2 do not. And MSVC gave me a warning about 2: "reference member is initialized to a temporary that doesn't persist after the constructor exits" Now I am wondering why they both make a temporary "double" object and pass it to boost::tuple<const double&> and only 2 failed.

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Multi-threading concept and lock in c#

- by Neeraj

I read about lock, though not understood nothing at all. My question is why do we use a un-used object and lock that and how this makes something thread-safe or how this helps in multi-threading ? Isn't there other way to make thread-safe code. public class test { private object Lock { get; set; } ... lock (this.Lock) { ... } ... } Sorry is my question is very stupid, but i don't understand, although i've used it many times.

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C# Asynchronous Sockets questions.

- by ccppjava

Based on my reading and testing, with asynchronous sockets, the socket itself can be passed using state object (IAsyncResult result), also if store the socket as a private field, it would be captured by the callback methods. I am wondering how the IAysnResult is kepted between the BeginXXX and ReceiveXXX? It looks to me that after the BeginXXX call and the method ends, the state object would be disposed by GC if there is no reference to it. In the case of private field, how the private field is shared between threads? (As far as I know, a callback is executed using a thread from the default thread pool, which would be considered as a new thread.) Many thanks, hope the questions themselves are clear.

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Help understanding this stack trace

- by user80632

Hi I have health monitoring turned on, and i have the following error i'm trying to understand: Exception: Exception information: Exception type: System.InvalidCastException Exception message: Specified cast is not valid. Thread information: Thread ID: 5 Thread account name: NT AUTHORITY\NETWORK SERVICE Is impersonating: False Stack trace: at _Default.Repeater1_ItemDataBound(Object sender, RepeaterItemEventArgs e) at System.Web.UI.WebControls.Repeater.CreateControlHierarchy(Boolean useDataSource) at System.Web.UI.WebControls.Repeater.OnDataBinding(EventArgs e) at _Default.up1_Load() at _Default.Timer1_Tick(Object sender, EventArgs e) at System.Web.UI.Timer.OnTick(EventArgs e) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) I'm just trying to figure out exactly where the problem is happening and what it is - is it happening in the Repeater1_ItemDataBound sub routine, or in the Timer1_Tick sub routine? Is the last thing that happened before the error occured at the top or bottom of the trace? any help much appreciated thanks

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- by Michael

- by Stephen

- by Grant

- by Ema

- by Yan Cheng CHEOK

- by nCdy

- by Hugh Perkins

- by Can Ho

- by Jakub Hampl

- by Nazgulled

- by Nate

- by flexage

- by Kazoom

- by Sandeep

- by DayOne

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- by Jimmy

- by Kevin

- by Xaqron

- by Spiderman

- by Ankur

- by Answeror

- by Neeraj

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