c# data matrix code RELIABLE RESOURCE MANAGEMENT in C#.NET

Generation Data Matrix 2d barcode in C#.NET RELIABLE RESOURCE MANAGEMENT

CHAPTER 11 RELIABLE RESOURCE MANAGEMENT
ECC200 Generator In Visual C#
Using Barcode printer for VS .NET Control to generate, create Data Matrix 2d barcode image in Visual Studio .NET applications.
www.OnBarcode.com
Data Matrix ECC200 Decoder In Visual C#
Using Barcode decoder for VS .NET Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
When an asynchronous exception is thrown after the call to the native XYZConnect function but before the returned handle is assigned to the Handle property, a resource is correctly allocated, but the handle is not stored in the wrapper object. Therefore, the finalizer of the wrapper class cannot use this handle for cleanup. A similar problem can occur in the destructor: ~XYZHandle() { if (hxyz) { ::XYZDisconnect(hxyz); hxyz = 0; } GC::KeepAlive(this); } When an asynchronous exception is thrown after the call to XYZDisconnect but before 0 is assigned to hxyz, a further Dispose call could cause double cleanup. If you use the thread-safe variant based on InterlockedExchangePointer, you will likely end up with a resource leak instead of double cleanup. To avoid asynchronous exceptions in these critical phases, the CLR version 2.0 provides a set of very special features. Each of these features targets different kinds of asynchronous exceptions, which are discussed in the following sections.
GS1 - 12 Creator In C#.NET
Using Barcode generation for .NET Control to generate, create GTIN - 12 image in VS .NET applications.
www.OnBarcode.com
UPC - 13 Maker In Visual C#
Using Barcode printer for VS .NET Control to generate, create EAN-13 image in Visual Studio .NET applications.
www.OnBarcode.com
ThreadAbortException
Barcode Printer In C#.NET
Using Barcode printer for VS .NET Control to generate, create Barcode image in .NET framework applications.
www.OnBarcode.com
Matrix Generation In C#.NET
Using Barcode encoder for Visual Studio .NET Control to generate, create 2D image in .NET applications.
www.OnBarcode.com
A typical asynchronous exception is System::Threading::ThreadAbortException, which is thrown to abort a thread. The most obvious way a thread can be aborted is the Thread.Abort API. Version 2.0 of the CLR guarantees that a ThreadAbortException is not thrown inside a catch or a finally block. This feature prevents error handling and cleanup code from being rudely interrupted. If you want to ensure that a ThreadAbortException cannot be thrown between the native call that allocates a native resource and the storage of the native handle in the wrapper class, you can modify your code so that both operations are executed inside a finally block. The following code solves the problem: XYZConnection() { try {} finally { xyzHandle.Handle = ::XYZConnect(); } }
Creating Barcode In C#.NET
Using Barcode printer for .NET Control to generate, create Barcode image in VS .NET applications.
www.OnBarcode.com
Generating Identcode In Visual C#
Using Barcode printer for VS .NET Control to generate, create Identcode image in VS .NET applications.
www.OnBarcode.com
CHAPTER 11 RELIABLE RESOURCE MANAGEMENT
Data Matrix Recognizer In Java
Using Barcode reader for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
Encoding Data Matrix In .NET
Using Barcode generation for ASP.NET Control to generate, create Data Matrix image in ASP.NET applications.
www.OnBarcode.com
In a very similar way, the shutdown logic can be implemented: ~XYZHandle() { try {} finally { if (hxyz) { ::XYZDisconnect(hxyz); hxyz = 0; } } GC::KeepAlive(this); } One may criticize that this code misuses a well-known language construct, but using try...finally in this scenario is part of an officially recommended pattern for reliable resource cleanup. The following explanations complete the discussion of this pattern by discussing the other asynchronous exceptions mentioned previously.
Paint UPC-A Supplement 2 In .NET
Using Barcode printer for ASP.NET Control to generate, create UPC Symbol image in ASP.NET applications.
www.OnBarcode.com
GS1 DataBar-14 Drawer In Java
Using Barcode encoder for Java Control to generate, create GS1 DataBar-14 image in Java applications.
www.OnBarcode.com
StackOverflowException
Making Denso QR Bar Code In Java
Using Barcode drawer for Android Control to generate, create Quick Response Code image in Android applications.
www.OnBarcode.com
Make Code 128B In None
Using Barcode creation for Font Control to generate, create Code-128 image in Font applications.
www.OnBarcode.com
The second asynchronous exception that is important for reliable resource management is System::StackOverflowException. The managed stack in the CLR is heavily based on the native stack. Elements pushed on the managed stack exist either on the native stack or in processor registers. A System::StackOverflowException occurs as a result of a native stack overflow exception, which is a Win32 SEH exception with the exception code EXCEPTION_STACK_OVERFLOW (=0xC00000FD). A stack overflow exception can be very difficult to handle properly because the lack of stack space does not leave many options for reacting. Calling a function implies pushing all parameters and the return address on the stack that has just run out of space. After a stack overflow, such an operation will likely fail. In the resource allocation code shown following, a stack overflow could in fact occur after the native function is called, but before the property setter for the handle property finishes its work: XYZConnection() { try {} finally { xyzHandle.Handle = ::XYZConnect(); } }
QR-Code Maker In Objective-C
Using Barcode drawer for iPhone Control to generate, create QR Code 2d barcode image in iPhone applications.
www.OnBarcode.com
Making Matrix Barcode In .NET Framework
Using Barcode encoder for ASP.NET Control to generate, create Matrix image in ASP.NET applications.
www.OnBarcode.com
CHAPTER 11 RELIABLE RESOURCE MANAGEMENT
EAN / UCC - 13 Creation In .NET Framework
Using Barcode generator for ASP.NET Control to generate, create EAN-13 Supplement 5 image in ASP.NET applications.
www.OnBarcode.com
Create UPC Symbol In None
Using Barcode encoder for Software Control to generate, create GS1 - 12 image in Software applications.
www.OnBarcode.com
Instead of providing some smart features to handle a StackOverflowException, version 2.0 of the CLR comes with a feature that tries to forecast the lack of stack space so that a StackOverflowException is thrown before you actually start executing critical code. To achieve this, the code can be modified like this: XYZConnection() { using System::Runtime::CompilerServices::RuntimeHelpers; RuntimeHelpers::PrepareConstrainedRegions(); try {} finally { xyzHandle.Handle = ::XYZConnect(); } } The same approach can also be used for the cleanup code inside the XYZHandle class: ~XYZHandle() { using System::Runtime::CompilerServices::RuntimeHelpers; RuntimeHelpers::PrepareConstrainedRegions(); try {} finally { if (hxyz) { ::XYZDisconnect(hxyz); hxyz = 0; } } GC::KeepAlive(this); } The pattern used here is called a constrained execution region (CER). A CER is a piece of code implemented in a finally block that follows a try block that is prefixed with a call to PrepareConstrainedRegions. From the namespace name System::Runtime::CompilerServices, you can assume that the intention of the CLR developers was that .NET languages should hide this construct behind nicer language features. Future versions of the C++/CLI compiler will hopefully allow you to write the following code instead: // not supported by Visual C++ 2005, but hopefully in a later version __declspec(constrained) XYZConnection() { xyzHandle.Handle = ::XYZConnect(); }
Data Matrix ECC200 Scanner In Visual Studio .NET
Using Barcode scanner for .NET framework Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
UPC-A Supplement 2 Recognizer In VB.NET
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Copyright © OnBarcode.com . All rights reserved.