In recent years, Visual Basic has won great acclaim for granting programmers the tools for creating highly detailed user interfaces via an intuitive form designer, along with an easy to learn programming language that together produced probably the best environment for rapid application development out there. One of the things that Visual Basic does, and other rapid application development tools, such as Delphi, also does, is provide access to a number of prefabricated controls that the developer can use to quickly build the user interface (UI) for an application.
At the center of most Visual Basic Windows applications stands the form designer. You create a user interface by dragging and dropping controls from a toolbox to your form, placing them where you want them to be when you run the program, and then double-clicking the control to add handlers for the control. The controls provided out of the box by Microsoft along with custom controls that can be bought at reasonable prices, have supplied programmers with an unprecedented pool of reusable, thoroughly tested code that is no further away than a click with the mouse. What was central to Visual Basic is now, through Visual Studio.NET, available to C# programmers.
Most of the controls used before .NET were, and still are, special COM objects, known as ActiveX controls. These are usually able to render themselves at both design and runtime. Each control has a number of properties allowing the programmer to do a certain amount of customization, such as setting the background color, caption, and its position on the form. The controls that we'll see in this chapter have the same look and feel as ActiveX controls, but they are not – they are .NET assemblies. However, it is still possible to use the controls that have been designed for older versions of Visual Studio but there is a small performance overhead because .NET has to wrap the control when you do so. For obvious reasons, when they designed .NET, Microsoft did not want to render the immense pool of existing controls redundant, and so have provided us with the means to use the old controls, even if future controls are built as pure .NET components.
These .NET assemblies can be designed in such a way that you will be able to use them in any of the Visual Studio languages, and the hope and belief is that the growing component industry will latch on, and start producing pure .NET components. We'll look at creating control ourselves in the next chapter.
An in depth explanation of .NET assemblies is provided in Chapter 21. Please refer to it if you want to know more about what an assembly is.
We have already seen the form designer in action, if only briefly, in the examples provided earlier in this book. In this chapter, we'll take a closer look at it, and especially how we use a number of controls, all of which come out of the box with Visual Studio.NET. Presenting all of the controls present in Visual Studio.NET will be an impossible task within the scope of this book, and so we'll be presenting the most commonly used controls, ranging from labelsand text boxes, to list views and status bars.
The Windows Form Designer
We'll start out by taking a brief tour of the Windows Form Designer. This is the main playing ground when you are laying out your user interface. It is perfectly possible to design forms without using Visual Studio.NET, but designing an interface in Notepad can be a quite painful experience.
Let's look at the environment we'll be using. Start Visual Studio.NET and create a new C# Windows Application project by selecting File | New | Project. In the dialog that appears, click Visual C# Projects in the tree to the left and then select Windows Application in the list to the right. For now, simply use the default name suggested by Visual Studio and click OK. This should bring up a window much like the one shown below:
If you are famliar with the forms designer found in Visual Basic you will notice the similarities – obviously someone desided that the designer was a winner and desided to allow it to be used it in other Visual Studio languages as well. If you are not familiar with the Visual Basic designer, then quite a few things are going on in the above screenshot, so let's take a moment and go through the panels one by one.
In the center of the screen is the form that you are designing. You can drag and drop controls from the toolbox onto the form. The toolbox is collapsed in the picture above, but if you move the mouse pointer to the far left of the screen over the Toolbox tab, it will unfold. You can then click the pin at the top right of the panel to pin it down. This will rearrange the work area so that the toolbox is now always on top, and isn't obscuring the form. We'll take a closer look at the toolbox and what it contains shortly.
Also collapsed on the left hand bar is the Server Explorer – represented by the computers icon on top of the toolbox tab. You can think of this as a small version of the Windows Control Panel. From here, you can browse computers on a network, add and remove database connections, and much more.
To the right of the window are two panels. The top-right one is the Solution Explorer and the class view. In the Solution Explorer, you can see all open projects and their associated files. By clicking the tab at the bottom of the Solution Explorer, you activate the Class Viewer. In this, you can browse all of the classes in your projects and all of the classes that they are derived from.
At the bottom right of the screen, is the Properties panel. This panel will contain all of the properties of the selected item for easy reference and editing. We'll be using this panel quite a bit in this chapter.
Also in this panel, the Dynamic Help tab is visible. This panel will show help tips to you for any selected objects and code even while you type. If your computer uses one of the older microprocessors or has a small amount of RAM, then I suggest that you remove this from the panel when it is not needed, as all that searching for help can make performance rather sluggish.
The Toolbox
Let's have a closer look at the toolbox. If you haven't already, move your mouse pointer over the toolbox on the left of the screen, and pin it to the foreground by clicking the pin at the top right of the panel that unfolds:
If you accidentally remove the toolbox by clicking the X instead, you can make it reappear by selecting Toolbox from the View menu, or by pressing Ctrl-Alt-X.
The toolbox contains a selection of all the controls available to you as a .NET developer. In particular, it provides the selection that is of importance to you as a Windows Application developer. If you had chosen to create a Web Forms project, rather than a Windows Application, you would have been given a different toolbox to use. You are not limited to use this selection. You can customize the toolbox to fit your needs, but in this chapter, we'll be focusing on the controls found in the selection that is shown in the picture above – in fact, we'll look at most of the controls that are shown here.
Now that we know where we'll be doing the work, let's look at controls in general.
Controls
Most controls in .NET derive from the System.Windows.Forms.Control class. This class defines the basic functionality of the controls, which is why many properties and events in the controls we'll see are identical. Many of these classes are themselves base classes for other controls, as is the case with the Label and TextBoxBase classes in the diagram below:
Some controls, named custom or user controls, derive from another class: System.Windows.Forms.UserControl. This class is itself derived from the Control class and provides the functionality we need to create controls ourselves. We'll cover this class in Chapter 14. Incidentally, controls used for designing Web user interfaces derive from yet another class, System.Web.UI.Control.
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