NET books seeking solutions for esoteric database programming, debugging, security, or printing challenges, but can't ever find them? Are you wrestling with VB. NET's newer topics, such as asynchronous programming, Web services, employing Office objects, using reflection, and the. NET Compact Framework? Could you use some assistance making the transition from VB6 to VB. If so, peer inside. NET More details. Diposting oleh mbahjenggot di Berbagi ke Twitter Berbagi ke Facebook.
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For Visual Studio , we have release all components as separate extensions. Furthermore, multiple events can be handled with the same handler by specifying additional events in the Handles clause:. See how much easier this is than the AddHandler and AddressOf approach?
This is an example of the gestalt of VB. When you are writing code and your variable types don't matter, you are practicing type-less programming. Type-less programming has a huge affect of making all versions of Visual Basic a rapid prototyping tool. It's perfect for building quick prototypes or function stubs when the final details, such as return types and parameter types, haven't been decided.
When designing VB. NET, one of the goals was to continue to support type-less programming in similar fashion to VB6. The switch that controls this type-less programming behavior is Option Strict. With Option Strict off the default , an Object can be used as a general type. With Option Strict on, the developer must explicitly specify the type of each expression.
This may involve adding CTypes, or conversion expressions, in key places or changing the types of variables. Aside from simple conversions, type-less programming also entails late binding. When compiling a piece of source code, the compiler must decide what each identifier represents.
Here's an example:. If not, the compiler generates an error that Print is not a member of Class1. Most of this binding work occurs at compile time; the compiler has determined exactly what members to call by the time it creates an. EXE or. Sometimes, however, this information is impossible to determine until the program actually runs, so the compiler defers binding until run time.
The process of binding deferral is called late binding. Late binding can also be thought of as type-less programming because type constraints are considered only at runtime. Depending on how the program runs, obj can hold an instance of any type. Because of this, the compiler has to treat obj. Print as a late bound call and wait until run time to determine what it does. The mechanism that determines what to call at run time is called the VB Late Binder.
If you were to analyze the IL that the compiler generates for the obj. If it succeeds, it makes the call. If it fails, the VB runtime throws a MissingMember exception. You can also dynamically load. NET assemblies and easily use their containing types without having to deal with the complexities of reflection and method invocation.
This code snippet dynamically loads an assembly called WidgetLibrary and instantiates an object of type Widget :. The beauty here is that you can use Widget just as you would any other type, except the compiler knows nothing about it when it builds the. All the method binding is performed at run time on an as-needed basis. Keep in mind that this flexibility comes at a sacrifice of some performance. But when you need to get a project off the ground as quickly as possible, late binding can be just the right catalyst.
Exposing a managed class to COM by hand is a confusing process that requires a good deal of COM programming knowledge. This makes the interface rather susceptible to versioning issues, especially when any of the base classes change. As an easy alternative, the ComClass attribute instructs the VB.
Listing 1 demonstrates how to use the ComClass attribute. Simply attach it to your public class and specify any optional GUIDs you would like used. The rest is taken care of for you. Listing 2 reveals what actually happens when you apply a ComClass attribute to your class. The details are beyond the scope of this article. However, what happens is that a class interface and event interface gets created and each of the corresponding members are decorated with the necessary attributes to specify DispIDs, default interfaces and GUIDs.
The ComClass attribute instructs the VB. Because the compiler performs all of this work for you, there is less complexity in your code and less opportunity for error. Instead, you have more time to spend on the important things, like architecture and algorithms. NET is undeniably a departure from previous versions. From running on top of a new platform, to gaining full object-oriented status, the Visual Basic of the next millennium is somewhat different from days of yore. However, the focal point for all versions of Visual Basic, past, present and future is and will always be making you a better, more productive programmer.
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Contact Us. Dark Kimbie. Published in:. Visual BasicR. NET concep. Visual Basic is the most popular programming language in existence. At the present time, it is estimated that there are. The book goes into highly specific detail about topics given short shrift in other books. For example, Petroutsos goes b. Visual Basic. NET Unleashed is a complete book on the fundamentals of programming with a fully object-oriented language f.
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