.net ean 13

.net ean 13

asp.net ean 13

.net ean 13

.net ean 13

vb.net ean 13,
asp.net ean 13,

.net ean 13,

asp.net ean 13,
vb.net ean-13 barcode,
.net ean 13,
.net ean 13,
vb.net ean-13 barcode,
vb.net ean-13 barcode,
asp.net ean 13,
.net ean 13,
asp.net ean 13,
vb.net ean-13 barcode,
asp.net ean 13,
vb.net ean 13,
vb.net ean-13 barcode,
asp.net ean 13,
vb.net ean-13 barcode,
asp.net ean 13,
.net ean 13,
asp.net ean 13,

vb.net ean 13,
vb.net ean 13,
asp.net ean 13,
vb.net ean 13,
.net ean 13,
asp.net ean 13,
.net ean 13,
asp.net ean 13,
vb.net ean 13,
vb.net ean-13 barcode,
vb.net ean-13 barcode,
.net ean 13,
.net ean 13,
vb.net ean-13 barcode,
.net ean 13,
vb.net ean 13,
.net ean 13,
vb.net ean 13,
vb.net ean-13 barcode,
vb.net ean-13 barcode,
vb.net ean 13,
.net ean 13,
asp.net ean 13,
.net ean 13,
vb.net ean-13 barcode,
vb.net ean-13 barcode,
vb.net ean-13 barcode,
asp.net ean 13,
vb.net ean 13,
vb.net ean-13 barcode,
asp.net ean 13,
vb.net ean-13 barcode,
vb.net ean-13 barcode,
vb.net ean 13,
asp.net ean 13,
vb.net ean 13,
.net ean 13,
vb.net ean 13,
vb.net ean-13 barcode,
vb.net ean-13 barcode,
vb.net ean-13 barcode,
.net ean 13,
.net ean 13,
asp.net ean 13,
vb.net ean 13,
asp.net ean 13,
vb.net ean 13,
asp.net ean 13,

There will be times during your application development that you will need a control that cannot be found in the Toolbox or in the component libraries You may also discover that you often create the same combination of controls on your Windows Forms or that you would like a particular control to exhibit extra functionality every time you use it All of these dilemmas can be solved by creating your own Windows Forms control Consider a text box control It has a number of properties, methods, and events that you can use when you add the control to your form But what if you wanted that same text box to accept only numeric input every time you used it Instead of changing its properties every time, you can create a new type of text box control that exhibits the behavior that you desire Often in a business application, you will find that a combination of controls is used to request a particular response from the user Each application you build must have the same controls added and their functionality combined By creating your own control that is built from the combination of these controls, you can reduce your development time greatly Finally, if you are in the business of creating user controls for development teams, you may find that you regularly take a blank control and draw its interface and provide its functionality from scratch In this chapter, we will investigate the ways you can create your own customized controls You may already be familiar with the term ActiveX controls These were the controls that Visual Basic programmers created and used Microsoft has moved away from that term, which had mostly Internet connotations, and, in order to simplify and clarify things, now calls any component that has a visible interface a control At this point in your OOP career, you should not find this kind of coding to be a mystery after all, isn t this just the same thing as building a class file in order to create reusable objects The only difference here is that you build a graphical interface into the component, with which the user can interact.

The Microsoft Visual C# NET Windows exam will test your knowledge of the three different ways of building custom controls: Extending an existing control Combining existing controls into a new composite control Designing and building a control from scratch In this section, we will consider the three types of controls and briefly describe their use, and later we will examine the process of creating a composite control from a combination of existing controls in detail Microsoft will likely test your knowledge of combining existing controls into a new single control, but we will look at all three methods individually The combined control is probably the control most commonly built (unless you are a control developer and build your own from scratch) EXAM TIP There are three ways to build your own controls: inherit from an existing control, combine existing controls into a new control, or design and build your own control from scratch

_____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____

In order to change or increase the functionality of an existing control, you can simply inherit from the base control, which gives you the base properties, methods, and events, and allows you to add what you need To illustrate this, we will extend the standard button and add our own fine-tuning to its base functionality Our new button will have an extra property called ButtonName that will allow the user to set and retrieve a name for the button

To begin, start a new project that uses the Windows Control Library by selecting File | New | Project From the New Project dialog box, choose Windows Control Library as shown in Figure 22-1 Give the project a name that will reflect the type of control you are building For this example, name the project NewButtoncs By naming the project, you will also have given a name to the namespace to which your class will belong Once you are done, click OK You will notice that you do not see the standard Windows Form in this type of project Instead you see a UserControl interface (shown in the following illustration) We

Figure 22-1

71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105

will explore the UserControl interface in the Creating Composite Controls section, when we build controls that are made up of multiple existing controls

Once the new project has been created, you need to do a little housekeeping in order to name the class file and the constructor appropriately Rename UserControl1cs in the Solution Explorer to the name you chose (for this example, name it NewButtoncs) Then switch to code view and rename the class file to NewButton and the constructor to NewButton Now examine the code carefully You will see that the class file definition looks like this:

This is the inheritance line that you must change if you want to inherit from an existing control Our specifications state that our new control will have most of the functionality of a regular Button control, along with our own special additions You must, therefore, change this line to read as follows:

_____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____ _____

By changing this line, you have effectively created a new control that derives from the Button class Your new control will have all the methods, properties, and events of a Button, and you can modify or add to that Save and build your project before continuing In order to create a new property that will allow us to set and retrieve the button s name, you now need to add your own property to the code ButtonName Start by creating a private variable to store the new property: