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• IEnumerator: Is it normal to have an empty Dispose method?

  - by C. Ross

  I'm writing an IEnumerator<T> class to iterate over a COM collection I'm wrappering. I've noticed that IEnumerator<T> extends IDisposable, so I'm required to implement the Dispose method. However, I can't think of anything I would put there, as I only have a reference to the collection (which I wouldn't want being disposed at the end of a foreach), and an int for the index. Is it normal to leave the Dispose method empty?

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• Why are my connections not closed even if I explicitly dispose of the DataContext?

  - by Chris Simpson

  I encapsulate my linq to sql calls in a repository class which is instantiated in the constructor of my overloaded controller. The constructor of my repository class creates the data context so that for the life of the page load, only one data context is used. In my destructor of the repository class I explicitly call the dispose of the DataContext though I do not believe this is necessary. Using performance monitor, if I watch my User Connections count and repeatedly load a page, the number increases once per page load. Connections do not get closed or reused (for about 20 minutes). I tried putting Pooling=false in my config to see if this had any effect but it did not. In any case with pooling I wouldn't expect a new connection for every load, I would expect it to reuse connections. I've tried putting a break point in the destructor to make sure the dispose is being hit and sure enough it is. So what's happening? Some code to illustrate what I said above: The controller: public class MyController : Controller { protected MyRepository rep; public MyController () { rep = new MyRepository(); } } The repository: public class MyRepository { protected MyDataContext dc; public MyRepository() { dc = getDC(); } ~MyRepository() { if (dc != null) { //if (dc.Connection.State != System.Data.ConnectionState.Closed) //{ // dc.Connection.Close(); //} dc.Dispose(); } } // etc } Note: I add a number of hints and context information to the DC for auditing purposes. This is essentially why I want one connection per page load

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• Method returns an IDisposable - Should I dispose of the result, even if it's not assigned to anythin

  - by mjd79

  This seems like a fairly straightforward question, but I couldn't find this particular use-case after some searching around. Suppose I have a simple method that, say, determines if a file is opened by some process. I can do this (not 100% correctly, but fairly well) with this: public bool IsOpen(string fileName) { try { File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None); } catch { // if an exception is thrown, the file must be opened by some other process return true; } } (obviously this isn't the best or even correct way to determine this - File.Open throws a number of different exceptions, all with different meanings, but it works for this example) Now the File.Open call returns a FileStream, and FileStream implements IDisposable. Normally we'd want to wrap the usage of any FileStream instantiations in a using block to make sure they're disposed of properly. But what happens in the case where we don't actually assign the return value to anything? Is it still necessary to dispose of the FileStream, like so: try { using (File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None)); { /* nop */ } } catch { return true; } Should I create a FileStream instance and dispose of that? try { using (FileStream fs = File.Open(fileName, FileMode.Open, FileAccess.Read, FileShare.None)); } ... Or are these totally unnecessary? Can we simply call File.Open and not assign it to anything (first code example), and let the GC dispose of it right away?

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• Implementing IDisposable on a subclass when the parent also implements IDisposable

  - by Tanzelax

  I have a parent and child class that both need to implement IDisposable. Where should virtual (and base.Dispose()?) calls come into play? When I just override the Dispose(bool disposing) call, it feels really strange stating that I implement IDisposable without having an explicit Dispose() function (just utilizing the inherited one), but having everything else. What I had been doing (trivialized quite a bit): internal class FooBase : IDisposable { Socket baseSocket; private void SendNormalShutdown() { } public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } private bool _disposed = false; protected virtual void Dispose(bool disposing) { if (!_disposed) { if (disposing) { SendNormalShutdown(); } baseSocket.Close(); } } ~FooBase() { Dispose(false); } } internal class Foo : FooBase, IDisposable { Socket extraSocket; private bool _disposed = false; protected override void Dispose(bool disposing) { if (!_disposed) { extraSocket.Close(); } base.Dispose(disposing); } ~Foo() { Dispose(false); } }

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• What's the purpose of GC.SuppressFinalize(this) in Dispose() method?

  - by mr.b

  I have code that looks like this: /// <summary> /// Dispose of the instance /// </summary> public void Dispose() { if (_instance != null) { _instance = null; // Call GC.SupressFinalize to take this object off the finalization // queue and prevent finalization code for this object from // executing a second time. GC.SuppressFinalize(this); } } Although there is a comment that explains purpose of that GC-related call, I still don't understand why it's there. Isn't object destined for garbage collection once all instances cease from existence (like, when used in using() block)? What's the use case scenario where this would play important role? Thanks!

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• How do I unit test a finalizer?

  - by GraemeF

  I have the following class which is a decorator for an IDisposable object (I have omitted the stuff it adds) which itself implements IDisposable using a common pattern: public class DisposableDecorator : IDisposable { private readonly IDisposable _innerDisposable; public DisposableDecorator(IDisposable innerDisposable) { _innerDisposable = innerDisposable; } #region IDisposable Members public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } #endregion ~DisposableDecorator() { Dispose(false); } protected virtual void Dispose(bool disposing) { if (disposing) _innerDisposable.Dispose(); } } I can easily test that innerDisposable is disposed when Dispose() is called: [Test] public void Dispose__DisposesInnerDisposable() { var mockInnerDisposable = new Mock<IDisposable>(); new DisposableDecorator(mockInnerDisposable.Object).Dispose(); mockInnerDisposable.Verify(x => x.Dispose()); } But how do I write a test to make sure innerDisposable does not get disposed by the finalizer? I want to write something like this but it fails, presumably because the finalizer hasn't been called by the GC thread: [Test] public void Finalizer__DoesNotDisposeInnerDisposable() { var mockInnerDisposable = new Mock<IDisposable>(); new DisposableDecorator(mockInnerDisposable.Object); GC.Collect(); mockInnerDisposable.Verify(x => x.Dispose(), Times.Never()); }

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• Exception when click DataGridview tab c#, .Net 4.0

  - by Nguyen Nam

  My winform app have two tab and multi thread, one is main tab and other is log tab. I only use log tab to show logs in a datagridview control. Exception is random occurred when click to log tab (Not click to row or colunm), i have try but can not find anyway to fix it. This is the error log: Message : Object reference not set to an instance of an object. Source : System.Windows.Forms TargetSite : System.Windows.Forms.DataGridViewElementStates GetRowState(Int32) StackTrace : at System.Windows.Forms.DataGridViewRowCollection.GetRowState(Int32 rowIndex) at System.Windows.Forms.DataGridView.ComputeHeightOfFittingTrailingScrollingRows(Int32 totalVisibleFrozenHeight) at System.Windows.Forms.DataGridView.GetOutOfBoundCorrectedHitTestInfo(HitTestInfo& hti, Int32& mouseX, Int32& mouseY, Int32& xOffset, Int32& yOffset) at System.Windows.Forms.DataGridView.OnMouseMove(MouseEventArgs e) at System.Windows.Forms.Control.WmMouseMove(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.DataGridView.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.Callback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) Message : Object reference not set to an instance of an object. Source : System.Windows.Forms TargetSite : Void ClearInternal(Boolean) StackTrace : at System.Windows.Forms.DataGridViewRowCollection.ClearInternal(Boolean recreateNewRow) at System.Windows.Forms.DataGridView.OnClearingColumns() at System.Windows.Forms.DataGridViewColumnCollection.Clear() at System.Windows.Forms.DataGridView.Dispose(Boolean disposing) at System.ComponentModel.Component.Dispose() at System.Windows.Forms.Control.Dispose(Boolean disposing) at System.ComponentModel.Component.Dispose() at System.Windows.Forms.Control.Dispose(Boolean disposing) at System.Windows.Forms.TabControl.Dispose(Boolean disposing) at System.ComponentModel.Component.Dispose() at System.Windows.Forms.Control.Dispose(Boolean disposing) at System.Windows.Forms.Form.Dispose(Boolean disposing) Update status code: private void updateMessage(int index, string message) { try { this.dgForums.Rows[index].Cells["ColStatus"].Value = message; System.Windows.Forms.Application.DoEvents(); } catch { } }

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• If I replace an image in a PictureBox control, should I dispose the original image first? .Net Winfo

  - by Jules

  Following on from my question here http://stackoverflow.com/questions/2548664/long-overdue-for-me-question-about-disposing-managed-objects-in-net-vb-net , If I replace an image in a picture box, should I dispose the original image first? Or, what about this situation: Dim bm As New Bitmap(32,32) bm = New Bitmap(32,32) bm = New Bitmap(32,32) bm = New Bitmap(32,32) Does bm need only to be disposed at the end, or should it be disposed before each re-creation?

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• How does one Dispose an object that is set in foreach?

  - by Greg Ogle

  foreach(var someDisposableObject in listOfDisposableObjects) { //some code someDisposableObject.Dispose(); //current code contains something like this. } Is there safe way, like a using clause to use in this scenario?

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• Do you still need to dispose attachments in .net v4 System.Net.Mail?

  - by JL

  With .net v3.5 or less it was required to manually dispose attachments after sending an email using SMTP client, is this still required in .net v4?

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• .NET CF 2.0: Stream implements IDisposable ... kind of?

  - by mvanbem

  I've run into something odd in a .NET CF 2.0 project for Pocket PC 2003 (Visual Studio 2005). I was dealing with a System.IO.Stream object and found that the IDE wouldn't auto-complete the Dispose() method. I typed it in manually and received: 'System.IO.Stream.Dispose(bool)' is inaccessible due to its protection level The error is referring to the protected Dispose(bool) method. Dispose() is either private or not present. Question 1: How is this possible? Stream implements IDisposable: public abstract class Stream : MarshalByRefObject, IDisposable ... and IDisposable requires a Dispose() method: public interface IDisposable { void Dispose(); } I know the compiler won't let me get away with that in my code. Question 2: Will I cause problems by working around and disposing my streams directly? IDisposable idisp = someStream; idisp.Dispose(); The implicit cast is accepted by the compiler.

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• Avoid Memory Leaks in SharePoint2010 Development

  - by ybbest

  When you develop SharePoint solution using code, you need to Dispose SPWeb appropriately to avoid memory Leaks. The general guideline for this are: Dispose Not to dispose OpenWebEnumerating Webs or AllWebs ParentWebRootWeb SPWeb from SPContext There are more rules than the one list above and as a smart SharePoint developer, you do not have to memories all the rules .There is a tool called SharePoint Dispose Checker which can help you to find potential memory leak. To use SPDisposeChecker in you solution, you need to download the tool from MSDN Code Gallery and install it in your development machine as follow. 1. Run the installer with elevated privilege. 2. Accept the agreement and click next. 3. Select those two options and click next. 4. Select Everyone and click Next. 5. Go to Toolsà SharePoint Dispose Check to Configure the SPDisposeCheck. 6. You can change the Treat problems as Errors to Warnings. 7. after clicking Save, you are all set to use the tool.Recompile my project , I can get the result below. References: SharePoint 2007/2010 “Do Not Dispose Guidance” + SPDisposeCheck

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• this.Dispose() Don't release memory used by Form after Closing it .

  - by Ehab Sutan

  Hello, in C# Application. I've a windows form application in which clicking certain button make object from a 2nd Form. On closing this 2nd From by user Memory used by this form not released (from Task Manager). I Tried using this.dispose() on exit button ,tried this.close() , tried form2 =null in the main code ,and tried clearing all controls from this form by code before Disposing and every time the clicks the button memory usage by the application increases more and memory used by previous instance not released. What shall i use to solve this problem ?

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• Disposing the members that implement IDisposable.

  - by Amby

  In my Dispose methods (like the one below), everytime i want to call someObj.Dispose() i also have a check for someObj!=null. Is that because of bad design on my part? Is their a cleaner way to ascertain that Dispose of all the members (implementing IDisposable) being used in an object is called without having a risk of NullReference exception ? protected void Dispose(bool disposing) { if (disposing) { if (_splitTradePopupManager != null) { _splitTradePopupManager.Dispose(); } } } Thanks for your interest.

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• What is a safe way to dispose of personal info on an old laptop and what to do with said laptop?

  - by MikeN

  I have an old laptop someone gave me that only has 64Megs of RAM on it and runs WIN XP. I wanted to wipe the drive clean by installing Ubuntu Desktop to remove any shred of personal information on it and to make it useful to someone else. But the Ubuntu installer keeps failing because there is not enough RAM. Is there another version of Linux that would easily install on a 64 Megs of RAM system? 2nd part of question, what do I do with this old laptop? It doesn't have a battery anymore and has to be plugged into the wall to run. Assuming I can install a good Linux distro on it, who do I give it to? Salvation Army? I'm looking to just have it be useful to someone or some organization for spare parts or some basic computer usage.

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• Excel I have a .Net object compiled as a tlb but cant not access any methods apart from Dispose.

  - by Mark O'Grady

  Hi This is ongoing issue to something I posted yesterday. I have a .net object that I want to use in Excel. I have an existing VBA script that i need to alter to call this the object from. I have then converted the object to a TLB. I've not really touched on this area before so any help will be appreciated. I have created an interface [Guid("0F700B48-E0CA-446b-B87E-555BCC317D74"),InterfaceType(ComInterfaceType.InterfaceIsDual)] [ComVisible(true)] public interface IOfficeCOMInterface { [DispId(1)] void ResetOrder(); [DispId(2)] void SetDeliveryAddress(string PostalName, string AddressLine1, string AddressLine2, string AddressLine3, string AddressLine4, string PostCode, string CountryCode, string TelephoneNo, string FaxNo, string EmailAddress); } I have also created an class that inherits that object. [ClassInterface(ClassInterfaceType.None), ProgId("NAMESPACE.OfficeCOMInterface"), Guid("9D9723F9-8CF1-4834-BE69-C3FEAAAAB530"), ComVisible(true)] public class OfficeCOMInterface : IOfficeCOMInterface, IDisposable { public void ResetSOPOrder() { } public void SetDeliveryAddress(string PostalName, string AddressLine1, string AddressLine2, string AddressLine3, string AddressLine4, string PostCode, string CountryCode, string TelephoneNo, string FaxNo, string EmailAddress) { try { SalesOrder.AmendDeliveryAddress(PostalName, AddressLine1, AddressLine2, AddressLine3, AddressLine4, PostCode); MessageBox.Show("Delivery address set"); } catch (Exception ex) { throw ex; } } } I can't access the object methods apart from dispose, I guess IDisposable is working fine. Is there anything I need to my Interface?

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• C# XP Sound QuickFix

  - by ikurtz

  I have this: ThreadPool.QueueUserWorkItem(new WaitCallback(FireAttackProc), fireResult); and FireAttackProc: private void FireAttackProc(Object stateInfo) { // Process Attack/Fire (local) lock (_procLock) { // build status message String status = "(Away vs. Home)"; // get Fire Result state info FireResult fireResult = (FireResult)stateInfo; // update home grid with attack information GameModel.HomeCellStatusSet(fireResult.FireGridLocation, Cell.cellState.Lock); this.Invoke(new Action(delegate() { RefreshHomeGrid(); })); status = status + "(Attack Coordinate: (" + GameModel.alphaCoords(fireResult.FireGridLocation.Column) + "," + fireResult.FireGridLocation.Row + "))(Result: "; // play audio data if true if (audio) { String Letters; Stream stream; SoundPlayer player; Letters = GameModel.alphaCoords(fireResult.FireGridLocation.Column); stream = Properties.Resources.ResourceManager.GetStream("_" + Letters); player = new System.Media.SoundPlayer(stream); player.PlaySync(); Letters = fireResult.FireGridLocation.Row.ToString(); stream = Properties.Resources.ResourceManager.GetStream("__" + Letters); player = new System.Media.SoundPlayer(stream); player.PlaySync(); stream.Dispose(); player.Dispose(); } if (audio) { SoundPlayer fire = new SoundPlayer(Properties.Resources.fire); fire.PlaySync(); fire.Dispose(); } // deal with hit/miss switch (fireResult.Hit) { case true: this.Invoke(new Action(delegate() { GameModel.HomeCellStatusSet(fireResult.FireGridLocation, Cell.cellState.Hit); status = status + "(Hit)"; })); if (audio) { SoundPlayer hit = new SoundPlayer(Properties.Resources.firehit); hit.PlaySync(); hit.Dispose(); } break; case false: this.Invoke(new Action(delegate() { GameModel.HomeCellStatusSet(fireResult.FireGridLocation, Cell.cellState.Miss); status = status + "(Miss)"; })); GameModel.PlayerNextTurn = NietzscheBattleshipsGameModel.GamePlayers.Home; if (audio) { SoundPlayer miss = new SoundPlayer(Properties.Resources.firemiss); miss.PlaySync(); miss.Dispose(); } break; } // refresh home grid with updated data this.Invoke(new Action(delegate() { RefreshHomeGrid(); })); GameToolStripStatusLabel.Text = status + ")"; // deal with ship destroyed if (fireResult.ShipDestroyed) { status = status + "(Destroyed: " + GameModel.getShipDescription(fireResult.DestroyedShipType) + ")"; if (audio) { Stream stream; SoundPlayer player; stream = Properties.Resources.ResourceManager.GetStream("_home"); player = new System.Media.SoundPlayer(stream); player.PlaySync(); player.Dispose(); stream.Dispose(); string ShipID = fireResult.DestroyedShipType.ToString(); stream = Properties.Resources.ResourceManager.GetStream("_" + ShipID); player = new System.Media.SoundPlayer(stream); player.PlaySync(); player.Dispose(); stream.Dispose(); stream = Properties.Resources.ResourceManager.GetStream("_destroyed"); player = new System.Media.SoundPlayer(stream); player.PlaySync(); player.Dispose(); stream.Dispose(); } } // deal with win condition if (fireResult.Win) { if (audio) { Stream stream; SoundPlayer player; stream = Properties.Resources.ResourceManager.GetStream("_home"); player = new System.Media.SoundPlayer(stream); player.PlaySync(); player.Dispose(); stream = Properties.Resources.ResourceManager.GetStream("_loses"); player = new System.Media.SoundPlayer(stream); player.PlaySync(); player.Dispose(); } GameModel.gameContracts = new GameContracts(); } // update status message if (fireResult.Hit) { if (!fireResult.Win) { status = status + "(Turn: Away)"; LockGUIControls(); } } // deal with turn logic if (GameModel.PlayerNextTurn == NietzscheBattleshipsGameModel.GamePlayers.Home) { this.Invoke(new Action(delegate() { if (!fireResult.Win) { status = status + "(Turn: Home)"; AwayTableLayoutPanel.Enabled = true; } })); } // deal with win condition if (fireResult.Win) { this.Invoke(new Action(delegate() { status = status + "(Game: Home Loses)"; CancelToolStripMenuItem.Enabled = false; NewToolStripMenuItem.Enabled = true; LockGUIControls(); })); } // display completed status message GameToolStripStatusLabel.Text = status + ")"; } } The issue is this: Under Vista/win7 the sound clips in the FireAttackProc plays. But under XP the logic contained within FireAttackProc gets executed but none of the sound clips play. Is there a quick solution to this so the sound will play under XP? I ask for a quick solution because i am happy being able to execute fully in Vista/Win7 but would be great if there was a quick solution so it would be XP compitable also. Thank you.

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• problem disposing class in Dictionary it is Still in the heap memory although using GC.Collect

  - by Bahgat Mashaly

  Hello i have a problem disposing class in Dictionary this is my code private Dictionary<string, MyProcessor> Processors = new Dictionary<string, MyProcessor>(); private void button1_Click(object sender, EventArgs e) { if (!Processors.ContainsKey(textBox1.Text)) { Processors.Add(textBox1.Text, new MyProcessor()); } } private void button2_Click(object sender, EventArgs e) { MyProcessor currnt_processor = Processors[textBox1.Text]; Processors.Remove(textBox2.Text); currnt_processor.Dispose(); currnt_processor = null; GC.Collect(); } public class MyProcessor: IDisposable { private bool isDisposed = false; string x = ""; public MyProcessor() { for (int i = 0; i < 20000; i++) { //this line only to increase the memory usage to know if the class is dispose or not x = x + "gggggggggggg"; } this.Dispose(); GC.SuppressFinalize(this); } public void Dispose() { this.Dispose(true); GC.SuppressFinalize(this); } public void Dispose(bool disposing) { if (!this.isDisposed) { isDisposed = true; this.Dispose(); } } ~MyProcessor() { Dispose(false); } } i use "ANTS Memory Profiler" to monitor heap memory the disposing work only when i remove all keys from dictionary how can i destroy the class from heap memory ? thanks in advance

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• Does EF 4 Code First's ContextBuilder Dispose its SqlConnection?

  - by Eric J.

  Looking at Code First in ADO.Net EF 4 CTP 3 and wondered how the SqlConnection in their walkthrough is disposed. Is that the responsibility of ContextBuilder? Is it missing from the example? var connection = new SqlConnection(DB_CONN); var builder = new ContextBuilder<BloggingModel>(); var connection = new SqlConnection(DB_CONN); using (var ctx = builder.Create(connection)) { //... }

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• how to dispose a incoming email and then send some words back using googe-app-engine..

  - by zjm1126

  from google.appengine.api import mail i read the doc: mail.send_mail(sender="[email protected]", to="Albert Johnson <[email protected]>", subject="Your account has been approved", body=""" Dear Albert: Your example.com account has been approved. You can now visit http://www.example.com/ and sign in using your Google Account to access new features. Please let us know if you have any questions. The example.com Team """) and i know hwo to send a email using gae ,but how to check a email incoming, and then do something thanks

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• Clone LINQ To SQL object Extension Method throws object dispose exception....

  - by gtas

  Hello all, I have this extension method for cloning my LINQ To SQL objects: public static T CloneObjectGraph<T>(this T obj) where T : class { var serializer = new DataContractSerializer(typeof(T), null, int.MaxValue, false, true, null); using (var ms = new System.IO.MemoryStream()) { serializer.WriteObject(ms, obj); ms.Position = 0; return (T)serializer.ReadObject(ms); } } But while i carry objects with not all references loaded, while qyuerying with DataLoadOptions, sometimes it throws the object disposed exception, but thing is I don't ask for references that is not loaded (null). e.g. I have Customer with many references and i just need to carry on memory the Address reference EntityRef< and i don't Load anything else. But while i clone the object this exception forces me to load all the EntitySet< references with the Customer object, which might be too much and slow down the application speed. Any suggestions?

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• Best way to identify and dispose locked thread in java.

  - by Bala R

  I have to call a function 3rd party module on a new thread. From what I've seen, the call either completes quickly if everything went well or it just hangs for ever locking up the thread. What's a good way to start the thread and make the call and wait for a few secs and if the thread is still alive, then assuming it's locked up, kill (or stop or abandon) the thread without using any deprecated methods. I have something like this for now, but I'm not sure if this is the best way to do it and I want to avoid calling Thread.stop() as it's deprecated. Thanks. private void foo() throws Exception { Runnable runnable = new Runnable() { @Override public void run() { // stuff that could potentially lock up the thread. } }; Thread thread; thread = new Thread(runnable); thread.start(); thread.join(3500); if (thread.isAlive()) { thread.stop(); throw new Exception(); } }

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• Why can't Java/C# implement RAII?

  - by mike30

  Question: Why can't Java/C# implement RAII? Clarification: I am aware the garbage collector is not deterministic. So with the current language features it is not possible for an object's Dispose() method to be called automatically on scope exit. But could such a deterministic feature be added? My understanding: I feel an implementation of RAII must satisfy two requirements: 1. The lifetime of a resource must be bound to a scope. 2. Implicit. The freeing of the resource must happen without an explicit statement by the programmer. Analogous to a garbage collector freeing memory without an explicit statement. The "implicitness" only needs to occur at point of use of the class. The class library creator must of course explicitly implement a destructor or Dispose() method. Java/C# satisfy point 1. In C# a resource implementing IDisposable can be bound to a "using" scope: void test() { using(Resource r = new Resource()) { r.foo(); }//resource released on scope exit } This does not satisfy point 2. The programmer must explicitly tie the object to a special "using" scope. Programmers can (and do) forget to explicitly tie the resource to a scope, creating a leak. In fact the "using" blocks are converted to try-finally-dispose() code by the compiler. It has the same explicit nature of the try-finally-dispose() pattern. Without an implicit release, the hook to a scope is syntactic sugar. void test() { //Programmer forgot (or was not aware of the need) to explicitly //bind Resource to a scope. Resource r = new Resource(); r.foo(); }//resource leaked!!! I think it is worth creating a language feature in Java/C# allowing special objects that are hooked to the stack via a smart-pointer. The feature would allow you to flag a class as scope-bound, so that it always is created with a hook to the stack. There could be a options for different for different types of smart pointers. class Resource - ScopeBound { /* class details */ void Dispose() { //free resource } } void test() { //class Resource was flagged as ScopeBound so the tie to the stack is implicit. Resource r = new Resource(); //r is a smart-pointer r.foo(); }//resource released on scope exit. I think implicitness is "worth it". Just as the implicitness of garbage collection is "worth it". Explicit using blocks are refreshing on the eyes, but offer no semantic advantage over try-finally-dispose(). Is it impractical to implement such a feature into the Java/C# languages? Could it be introduced without breaking old code?

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• Is this correct for disposing an object using IDisposable

  - by robUK

  I have a class that implements the IDisposable interface. I am using a webclient to download some data using the AsyncDownloadString. I am wondering have I correctly declared my event handlers in the constructor and within the using statement of the web client? And is this correct way to remove the event handlers in the Dispose method? Overrule is this the correct way to use the IDisposable interface? public class Balance : IDisposable { //Constructor WebClient wc; public Balance() { using (wc = new WebClient()) { //Create event handler for the progress changed and download completed events wc.DownloadProgressChanged += new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged); wc.DownloadStringCompleted += new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted); } } ~Balance() { this.Dispose(false); } //Get the current balance for the user that is logged in. //If the balance returned from the server is NULL display error to the user. //Null could occur if the DB has been stopped or the server is down. public void GetBalance(string sipUsername) { //Remove the underscore ( _ ) from the username, as this is not needed to get the balance. sipUsername = sipUsername.Remove(0, 1); string strURL = string.Format("https://www.xxxxxxx.com", sipUsername); //Download only when the webclient is not busy. if (!wc.IsBusy) { // Download the current balance. wc.DownloadStringAsync(new Uri(strURL)); } else { Console.Write("Busy please try again"); } } //return and display the balance after the download has fully completed void wc_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e) { //Pass the result to the event handler } //Dispose of the balance object public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } //Remove the event handlers private bool isDisposed = false; private void Dispose(bool disposing) { if (!this.isDisposed) { if (disposing) { wc.DownloadProgressChanged -= new DownloadProgressChangedEventHandler(wc_DownloadProgressChanged); wc.DownloadStringCompleted -= new DownloadStringCompletedEventHandler(wc_DownloadStringCompleted); wc.Dispose(); } isDisposed = true; } } }

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• actionscript-3: refactor interface inheritance to get rid of ambiguous reference error

  - by maxmc

  hi! imagine there are two interfaces arranged via composite pattern, one of them has a dispose method among other methods: interface IComponent extends ILeaf { ... function dispose() : void; } interface ILeaf { ... } some implementations have some more things in common (say an id) so there are two more interfaces: interface ICommonLeaf extends ILeaf { function get id() : String; } interface ICommonComponent extends ICommonLeaf, IComponent { } so far so good. but there is another interface which also has a dispose method: interface ISomething { ... function dispose() : void; } and ISomething is inherited by ICommonLeaf: interface ICommonLeaf extends ILeaf, ISomething { function get id() : String; } As soon as the dispose method is invoked on an instance which implements the ICommonComponent interface, the compiler fails with an ambiguous reference error because ISomething has a method called dispose and ILeaf also has a dispose method, both living in different interfaces (IComponent, ISomething) within the inheritace tree of ICommonComponent. I wonder how to deal with the situation if the IComponent, the ILeaf and the ISomething can't change. the composite structure must also work for for the ICommonLeaf & ICommonComponent implementations and the ICommonLeaf & ICommonComponent must conform to the ISomething type. this might be an actionscript-3 specific issue. i haven't tested how other languages (for instance java) handle stuff like this.

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