dispose | 易学教程

What is IDisposable for?

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If .NET has garbage collection then why do you have to explicitly call IDisposable ? Jon Skeet Garbage collection is for memory. You need to dispose of non-memory resources - file handles, sockets, GDI+ handles, database connections etc. That's typically what underlies an IDisposable type, although the actual handle can be quite a long way down a chain of references. For example, you might Dispose an XmlWriter which disposes a StreamWriter it has a reference to, which disposes the FileStream it has a reference to, which releases the file handle itself. Expanding a bit on other comments: The

Should I always disconnect event handlers in the Dispose method?

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I'm working in C# and my workplace has some code standards. One of them is that each event handler we connect (such as KeyDown ) must be disconnected in the Dispose method. Is there any good reason for that? Unless you expect the publisher of the event to outlive the subscriber, there's no reason to remove the event handler, no. This is one of those topics where folk lore has grown up. You really just need to think about it in normal terms: the publisher (e.g. the button) has a reference to the subscriber. If both the publisher and the subscriber will be eligible for garbage collection at the

When is Dispose necessary?

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问题 When you have code like: Bitmap bmp = new Bitmap ( 100, 100 ); Graphics g = Graphics.FromImage ( bmp ); Pen p = new Pen ( Color.FromArgb ( 128, Color.Blue ), 1 ); Brush b = new SolidBrush ( Color.FromArgb ( 128, Color.Blue ) ); g.FillEllipse ( b, 0, 0, 99, 99 ); g.FillRegion ( b, pictureBox1.Region ); pictureBox1.BackColor = Color.Transparent; pictureBox1.Image = bmp; Do you have to dispose the pen and brush? What about bmp and the g? My main question is, if these were to be disposed manually

Dispose() for cleaning up managed resources?

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问题 In this answer I found, Cleanup the unmanaged resources in the Finalize method and the managed ones in the Dispose method, when the Dispose/Finalize pattern has been used in your code. And later I found this nice article about finalize and dispose and got a clear idea about them. The article has the following code( Page 3 ), to explain the concepts: class Test : IDisposable { private bool isDisposed = false; ~Test() { Dispose(false); } protected void Dispose(bool disposing) { if (disposing) {

Do I need to call Close() on a ManualResetEvent?

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问题 I've been reading up on .NET Threading and was working on some code that uses a ManualResetEvent. I have found lots of code samples on the internet. However, when reading the documentation for WaitHandle, I saw the following: WaitHandle implements the Dispose pattern. See Implementing Finalize and Dispose to Clean Up Unmanaged Resources. None of the samples seem to call .Close() on the ManualResetEvent objects they create, even the nice Recursion and Concurrency article from the pfxteam blog

When do we need to call Dispose() in dot net c#?

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问题 Do I need to dispose a sqldatareader after it is created? SqlDataReader reader; --- --- --- reader.Close(); reader.Dispose(); 回答1: Rule of thumb: if a class implements IDisposable you should always call the Dispose method as soon as you have finished using this resource. Even better wrap it in a using statement to ensure that the Dispose method will be called even if an exception is thrown: using (var reader = conn.ExecuteReader()) { ... } 回答2: Object which are Disposable can be best used (if

To Dispose or not to Dispose (CA2000)

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问题 I'm switching on Code Analysis on an older project. Most remarks that result I can understand, but the CA2000: Dispose objects before losing scope is hard to get right. For instance, this code from an ASP.Net page: private void BuildTable() { HtmlTableRow tr = new HtmlTableRow(); HtmlTableCell td = new HtmlTableCell(); tr.Cells.Add(td); // add some controls to 'td' theTable.Rows.Insert(0, tr); // 'theTable' is an HtmlTable control on the page } Gives CA messages: CA2000 : Microsoft

Difference between destructor, dispose and finalize method

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I am studying how garbage collector works in c#. I am confused over the use of Destructor , Dispose and Finalize methods. As per my research and understandings, having a Destructor method within my class will tell the garbage collector to perform the garbage collection in the way mentioned in the destructor method which cannot be called explicitly on the instances of the class. The Dispose method is meant to provide the user to control the garbage collection. The Finalize method frees the resources used by the class, but not the object itself. I am not sure if I understand it the right way.

How to dispose a class in .net?

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The .NET garbage collector will eventually free up memory, but what if you want that memory back immediately? What code do you need to use in a class MyClass to call MyClass.Dispose() and free up all the used space by variables and objects in MyClass ? IDisposable has nothing to do with freeing memory. IDisposable is a pattern for freeing unmanaged resources -- and memory is quite definitely a managed resource. The links pointing to GC.Collect() are the correct answer, though use of this function is generally discouraged by the Microsoft .NET documentation. Edit: Having earned a substantial

.NET object events and dispose / GC

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问题 EDIT: After Joel Coehoorns excellent answer, I understand that I need to be more specific, so I modified my code to be closer to thing I'm trying to understand... Events: As I understand, in the background the events are "collection" of EventHandlers aka Delegates which will be executed when event raised. So for me it means that if object Y has event E and object X subscribes to event Y.E , then Y will have reference to X, since Y must execute the method located in X, in that way, X can not