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Unit 4: Advanced Server Controls
3. RangeValidator Notes
4. RegularExpressionValidator
5. CustomValidator
6. Validation Summary
We can also customize validation for our own needs. Then, if there are any errors in the form
data, these validation server controls enable us to customize the display of error information
on the browser.
We place validation server controls on our page as we would any other type of controls. After the
user submits the form, the user’s form information is sent to the appropriate validation control,
where it is evaluated. If the information does not validate, the control sets a page property that
indicates this. After all the form information is sent to all the validation server controls, if one
or more of the validation server controls cannot validate the information sent to it, the entire
form input is found to be invalid, and the user is notified.(See Table 4.2)
Table 4.2: Available validation server controls
Validation Server Control Description
RequiredFieldValidator Ensures that the user does not skip a form entry field
CompareValidator Allows for comparisons between the user’s input and
another item using a comparison operator (equals,
greater than, less than
RangeValidator Checks the user’s input based upon a lower- and
upper-level range of numbers or characters
RegularExpressionValidator Checks that the user’s entry matches a pattern defined
by a regular expression. This is a good control to use
to check e-mail addresses and phone numbers
CustomValidator Checks the user’s entry using custom-coded
validation logic
Validation Summary Displays all the error messages from the valuators
in one specific spot on the page
The RequiredFieldValidator Control
The RequiredFieldValidator server control makes sure that the user enters something into the
field that it is associated with in the form. We need to tie the RequiredFieldValidator to each
control that is a required field in the form. Although this is the simplest of the validation server
controls, we must understand certain things about it.
To see an example of using the RequiredFieldValidator server control, create a Web form
that contains a Textbox server control and a Button server control. Next to the button, place a
RequiredFieldValidator server control. Our ASP.NET page should look like the code illustrated
in Listing 2. (See Figure 4.2)
Using the RequiredFieldValidator control
Visual C# .NET
<%@ Page Language= “VB” %>
<script runat= “server”>
Sub Button1_Click (sender As Object, e As EventArgs)
Label1.Text = “Page is valid!”
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