ASP.NET 2.0: A Developeramp;#039;s Notebook [Electronic resources] نسخه متنی

1.4. Define Multiple Validation Groups on a Page

In ASP.NET 1.x, all controls in a single page
are
validated together. For example, suppose you have a Search button and
a Get Title button, as shown in Figure 1-15. If you
use a RequiredFieldValidator validation control on the ISBN text box,
then clicking the Search button will not
result in a postback if the ISBN text box is empty. This is because
the entire page is invalidated as long as one control fails the
validation.

Figure 1-15. Multiple forms on a page

Note: By grouping controls into validation groups, you can now
independently validate collections of controls.

In ASP.NET 2.0, group validation allows controls in a page to be
grouped logically so that a postback in one group is not dependent on
another.

1.4.1. How do I do that?

The best way to explore this new feature is to create a form with
multiple postback controls, add a validator to one of them, and
then assign each control to a separate group. In this lab,
you'll implement the form shown in Figure 1-15.

Launch Visual Studio 2005 and create a new web site project. Name the
project C:\ASPNET20\chap01-Validation.

Populate the default Web Form with the Panel, TextBox, and Button
controls shown in Figure 1-16.

Figure 1-16. A page with multiple controls

In the top panel (Panel control 1), you'll configure
the Search button to post the search string to the server, which in
turn will redirect to Google's site. To do so,
double-click the Search button (btnSearch) and
enter the following code on the code-behind to redirect the search
string to Google's site:

Sub btnSearch_Click(ByVal sender As Object, _
ByVal e As System.EventArgs) _
Handles btnSearch.Click
Dim queryStr As String = HttpUtility.UrlEncode(txtSearch.Text)
Response.Redirect("http://www.google.com/search?q=" & queryStr)
End Sub

The TextBox control contained in the bottom panel (Panel control 2)
will take in an ISBN number and perhaps perform some processing (like
retrieve details of a book from Amazon.com). Associate the
RequiredFieldValidator control with the ISBN text box (you can
configure it in Source View):

<asp:RequiredFieldValidator 
ID="RequiredFieldValidator1" Runat="server" 
ErrorMessage="RequiredFieldValidator"
ControlToValidate="txtISBN" 
SetFocusOnError="True">
ISBN required</asp:RequiredFieldValidator>

To divide the controls into two separate validation groups, switch to
Source View and use the ValidationGroup attribute, as shown
in the following code sample
(highlighted in bold):

...
<asp:TextBox ID="txtSearch" Runat="server" 
Width="320px" Height="22px">
</asp:TextBox>
<asp:Button ID="btnSearch" Runat="server" 
Text="Search" ValidationGroup="SearchGroup" />
...
<asp:TextBox ID="txtISBN" Runat="server" 
Width="212px" Height="22px">
</asp:TextBox>
<asp:Button ID="btnGetTitle" Runat="server" 
Text="Get Title" 
ValidationGroup="BooksGroup" />
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" 
Runat="server" ErrorMessage="RequiredFieldValidator" 
ControlToValidate="txtISBN" 
ValidationGroup="BooksGroup">ISBN required
</asp:RequiredFieldValidator>
...

Here, the Search button is assigned the SearchGroup validation group,
while the Get Title button and the
RequiredFieldValidator are both assigned to the
BooksGroup validation group.

Press F5 to test the application. Now you can click the Search and
Get Title buttons independently of each other.

Tip: Controls that do not set the ValidationGroup attribute belong to the
default group, thus maintaining backward compatibility with ASP.NET
1.x.

1.4.2. What about...

...setting the focus on the field on error?

All validation controls in ASP.NET 2.0 now support
the SetFocusOnError
property. Simply set a validator control's
SetFocusOnError attribute to True so that the browser will set the
focus on the control on error.

In the previous example, if the RequiredFieldValidator control has
the SetFocusOnError attribute:

<asp:RequiredFieldValidator 
ID="RequiredFieldValidator1" Runat="server" 
ErrorMessage="RequiredFieldValidator"
ControlToValidate="txtISBN" 
ValidationGroup="BooksGroup" 
SetFocusOnError="True">

Then the ISBN text box will get the focus if you click the Get Title
button when the ISBN text box is empty.

1.4.3. Where can I learn more?

If you are interested in simulating the validation group behavior of
ASP.NET 2.0 in ASP.NET 1.x, check out http://weblogs.asp.net/skoganti/archive/2004/12/05/275457.aspx.