Build Your Own ASP.NET 2.0 Web Site Using C# & VB, Second Edition

JavaScript or clumsy server-side code to write by hand! Let’s take a look at these

ASP.NET validation controls in detail.

RequiredFieldValidator

The RequiredFieldValidator control is the simplest of the validation controls.

It does exactly what its name suggests: it makes sure that a user enters a value

into a web control. We used the RequiredFieldValidator control in the login

page example presented earlier:

File: Login.aspx (excerpt)

<p>

Username:<br />

<asp:TextBox id="usernameTextBox" runat="server" />

<asp:RequiredFieldValidator id="usernameReq" runat="server"

ControlToValidate="usernameTextBox"

ErrorMessage="Username is required!"

SetFocusOnError="True" Display="Dynamic" />

</p>

<!-- Password -->

<p>

Password and Confirmation:<br />

<asp:TextBox id="passwordTextBox" runat="server"

TextMode="Password" />

<asp:RequiredFieldValidator id="passwordReq" runat="server"

ControlToValidate="passwordTextBox"

ErrorMessage="Password is required!"

SetFocusOnError="True" Display="Dynamic" />

<asp:TextBox id="confirmPasswordTextBox" runat="server"

TextMode="Password" />

<asp:RequiredFieldValidator id="confirmPasswordReq"

runat="server" ControlToValidate="confirmPasswordTextBox"

ErrorMessage="Password confirmation is required!"

SetFocusOnError="True" Display="Dynamic" />

</p>

As you can see, three RequiredFieldValidator controls are used on this page.

The first validates the usernameTextBox control, the second validates the pass-

wordTextBox control, and the third validates the confirmPasswordTextBox

control. These assignments are made using the ControlToValidate property of

the RequiredFieldValidator controls. The ErrorMessage property contains

the error message that will be displayed when the user fails to enter a value into

each control.

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Chapter 6: Using the Validation Controls