End Property

Public Property BGColor As System.Drawing.Color Get

BGColor = Address.BackColor

End Get Set

Address.BackColor = value End Set

End Property </script>

Add this code to the top of the Address User Control file. Notice the last two properties listed, FontColor and BGColor. These properties will get and set the font color for all the User Control’s labels and the background color of the panel that contains the User Control’s controls. Now add the following code to the script block at the top of your ASP.NET page to test your new properties:

<script language=”VB” runat=”server”>

Sub Page_Load(Sender As Object, E As EventArgs) With AddressControl

.BGColor = System.Drawing.Color.Blue

.FontColor = System.Drawing.Color.White

.Address1 = “100 ASP.NET St.”

.City = “Microsoft”

.StateID = 3

.ZipCode = “11111” End With

End Sub </script>

Pretty cool, huh? As you can see, the amount of code you’ll need to write will be greatly reduced once you create a decent sized library of User Controls. And this is just the beginning; you could expose even more properties to make your controls infinitely customizable.

Writing Custom Control Methods

In addition to creating properties, you can write custom methods for a User Control. Custom methods can be used to populate a list box, validate controls, and so on. The possibilities are endless. In the following example, we will add a method to Address User Control that will validate user input and return a Boolean value (true or false) based on the result of the validation. Include the following code within the <script> block in the address.ascx page:

Public Function ValidateAddress() As Boolean If Trim(txtAddress1.text) = “” Then

return False Exit Function

End If

If Trim(txtCity.text) = “” Then return False

Exit Function End If

If cmbState.SelectedIndex = 0 Then return False

Exit Function End If

If Trim(txtZipCode.text) = “” Then return False

Exit Function End If

return True End Function

As you can see in the ValidateAddress method, we do a simple check of a few selected fields and return a Boolean value based on the result. Pretty simple stuff, but it illustrates implementing a User Control method fairly well. To test this method, simply add the following line of code to the ASP.NET page after declaring the server control:

<%

Response.Write(AddressControl.ValidateAddress)

%>

Implementing User Control Events

User Controls can also respond to events and even respond to ASP.NET events like

Page_OnLoad.

Try putting the following code in the <script> block of address.ascx:

Sub Page_Load(Sender As Object, E As EventArgs) If Not Page.isPostBack Then

Dim oItem As New ListItem With oItem

.Value = 10

.Text = “Georgia” End With cmbState.Items.Add(oItem)

End If End Sub

Now try running the ASP.NET page. A Georgia item should now appear in the State list box. Imagine writing a little routine in the User Control that could populate controls from a database.

Because User Controls are a collection of ASP.NET controls, you have to use the same methods as with ASP.NET if you want to implement a control event handler. The first thing you want to do is write an event handling method. Add the following method, called btnSubmit_Click for example, to the address.ascx file:

Private Sub btnSubmit_Click(Sender As Object, E As EventArgs) Response.Write(“Submit button was clicked!”)

End Sub

Now in the address.ascx file, change the btnSubmit button control declaration to the following:

<asp:Button ID=btnSubmit text=”Submit” onClick=”btnSubmit_Click” runat=”server” />

Try it out now! You see that now, not only is the Web Form submitted, but the btnSubmit_Click event is also processed. It’s that simple.

REVIEW

User Controls are a nice feature of ASP.NET. They essentially enable you to write reusable custom controls based on the standard HTML and Web controls. You can also add custom properties, methods, and events to allow runtime User Control customization and interaction. Using User Controls, you can improve application performance as well as maintainability.

QUIZ YOURSELF

1.What is a User Control? (See session introduction.)

2.What directive can you use in an ASP.NET page to import a User Control? (See “Creating a User Control.”)

3.Why shouldn’t you include the <html>, <body>, and <form> tags in a User Control? (See “Creating a User Control.”)

P A R T

III

Saturday

Afternoon

Session 11

Validating User Input

Session 12

Maintaining State in ASP.NET

Session 13

Authentication and Authorization

Session 14

ASP.NET Caching

Session 15

Introducing ADO.NET

Session 16

Navigating the ADO.NET Object Model