generate 2d barcode vb.net Part II Designing Types in Visual C#.NET

Creator PDF-417 2d barcode in Visual C#.NET Part II Designing Types

Part II Designing Types
PDF-417 2d Barcode Creator In C#.NET
Using Barcode maker for Visual Studio .NET Control to generate, create PDF417 image in .NET applications.
www.OnBarcode.com
PDF-417 2d Barcode Reader In Visual C#.NET
Using Barcode reader for .NET framework Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
improperly . If the field were public, any code could alter the value in the field and potentially wipe out all of the delegates that have registered interest in the event . The second construct the C# compiler generates is a method that allows other objects to register their interest in the event . The C# compiler automatically names this function by prepending add_ to the event s name (NewMail) . The C# compiler automatically generates the code that is inside this method . The code always calls System.Delegate s static Combine method, which adds the instance of a delegate to the list of delegates and returns the new head of the list, which gets saved back in the field . The third construct the C# compiler generates is a method that allows an object to unregister its interest in the event . Again, the C# compiler automatically names this function by prepending remove_ to the event s name (NewMail) . The code inside this method always calls Delegate s static Remove method, which removes the instance of a delegate from the list of delegates and returns the new head of the list, which gets saved back in the field . Warning If you attempt to remove a method that was never added, then Delegate s Remove
Bar Code Creator In C#
Using Barcode drawer for .NET Control to generate, create bar code image in VS .NET applications.
www.OnBarcode.com
Decode Bar Code In Visual C#.NET
Using Barcode scanner for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
method internally does nothing . That is, you get no exception or warning of any type; the event s collection of methods remains unchanged .
Draw PDF417 In .NET
Using Barcode generation for ASP.NET Control to generate, create PDF-417 2d barcode image in ASP.NET applications.
www.OnBarcode.com
Draw PDF417 In .NET
Using Barcode drawer for Visual Studio .NET Control to generate, create PDF417 image in .NET framework applications.
www.OnBarcode.com
Note The add and remove methods use a well-known pattern to update a value in a thread-safe
Encoding PDF417 In VB.NET
Using Barcode creation for .NET Control to generate, create PDF417 image in .NET framework applications.
www.OnBarcode.com
Data Matrix 2d Barcode Printer In Visual C#.NET
Using Barcode encoder for .NET framework Control to generate, create Data Matrix image in Visual Studio .NET applications.
www.OnBarcode.com
way . This pattern is discussed in the The Interlocked Anything Pattern section of 28 .
Paint EAN / UCC - 13 In Visual C#
Using Barcode drawer for .NET framework Control to generate, create EAN128 image in VS .NET applications.
www.OnBarcode.com
Creating Code-128 In Visual C#.NET
Using Barcode creator for Visual Studio .NET Control to generate, create Code 128C image in Visual Studio .NET applications.
www.OnBarcode.com
In this example, the add and remove methods are public . The reason they are public is that the original line of source code declared the event to be public . If the event had been declared protected, the add and remove methods generated by the compiler would also have been declared protected . So, when you define an event in a type, the accessibility of the event determines what code can register and unregister interest in the event, but only the type itself can ever access the delegate field directly . Event members can also be declared as static or virtual, in which case the add and remove methods generated by the compiler would be either static or virtual, respectively . In addition to emitting the aforementioned three constructs, compilers also emit an event definition entry into the managed assembly s metadata . This entry contains some flags and the underlying delegate type, and refers to the add and remove accessor methods . This information exists simply to draw an association between the abstract concept of an event and its accessor methods . Compilers and other tools can use this metadata, and this information can also be obtained by using the System.Reflection.EventInfo class . However, the CLR itself doesn t use this metadata information and requires only the accessor methods at runtime .
Print ANSI/AIM Code 39 In C#
Using Barcode creator for .NET framework Control to generate, create Code-39 image in .NET applications.
www.OnBarcode.com
Generating 2/5 Standard In C#.NET
Using Barcode generation for .NET Control to generate, create Industrial 2 of 5 image in .NET applications.
www.OnBarcode.com
11 Events
Decode Barcode In VS .NET
Using Barcode recognizer for .NET framework Control to read, scan read, scan image in VS .NET applications.
www.OnBarcode.com
Printing Data Matrix 2d Barcode In VS .NET
Using Barcode maker for VS .NET Control to generate, create DataMatrix image in .NET framework applications.
www.OnBarcode.com
Designing a Type That Listens for an Event
PDF 417 Recognizer In Visual Basic .NET
Using Barcode scanner for .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
Draw Data Matrix 2d Barcode In None
Using Barcode printer for Software Control to generate, create Data Matrix 2d barcode image in Software applications.
www.OnBarcode.com
The hard work is definitely behind you at this point . In this section, I ll show you how to define a type that uses an event provided by another type . Let s start off by examining the code for the Fax type:
Creating Bar Code In .NET
Using Barcode drawer for ASP.NET Control to generate, create barcode image in ASP.NET applications.
www.OnBarcode.com
Make Bar Code In Java
Using Barcode drawer for BIRT Control to generate, create barcode image in BIRT reports applications.
www.OnBarcode.com
internal sealed class Fax { // Pass the MailManager object to the constructor public Fax(MailManager mm) { // Construct an instance of the EventHandler<NewMailEventArgs> // delegate that refers to our FaxMsg callback method. // Register our callback with MailManager's NewMail event mm.NewMail += FaxMsg; } // This is the method the MailManager will call // when a new e-mail message arrives private void FaxMsg(Object sender, NewMailEventArgs e) { // 'sender' identifies the MailManager object in case // we want to communicate back to it. // 'e' identifies the additional event information // the MailManager wants to give us. // Normally, the code here would fax the e-mail message. // This test implementation displays the info in the console Console.WriteLine("Faxing mail message:"); Console.WriteLine(" From={0}, To={1}, Subject={2}", e.From, e.To, e.Subject); } // This method could be executed to have the Fax object unregister // itself with the NewMail event so that it no longer receives // notifications public void Unregister(MailManager mm) { // Unregister with MailManager's NewMail event mm.NewMail -= FaxMsg; } }
Painting EAN128 In Visual Studio .NET
Using Barcode generator for Visual Studio .NET Control to generate, create GS1 128 image in VS .NET applications.
www.OnBarcode.com
UCC-128 Recognizer In VB.NET
Using Barcode reader for VS .NET Control to read, scan read, scan image in Visual Studio .NET applications.
www.OnBarcode.com
When the e-mail application initializes, it would first construct a MailManager object and save the reference to this object in a variable . Then the application would construct a Fax object, passing the reference to the MailManager object as a parameter . In the Fax constructor, the Fax object registers its interest in MailManager s NewMail event using C# s += operator:
mm.NewMail += FaxMsg;
Copyright © OnBarcode.com . All rights reserved.