Building Custom Forms - ASP.NET Dynamic Data - page 332

countryTextBox.TextChanged += CountryTextBox_TextChanged;
}
private void CountryTextBox_TextChanged(object sender, EventArgs e)
{
var countryTextBox = (TextBox)sender;
this.autoCompleteExtender.ContextKey = countryTextBox.Text;
}
The overridden OnLoad method retrieves the TextBox control created by the
countryFieldTemplate through its DataControl property. It then assigns the
CountryTextBox_TextChanged method as an event handler to its TextChanged event. This
event handler is where you can access the current Country value from the text box and
store it in the ContextKey of the AutoCompleteExtender . Note that by default, changing a
value in a TextBox control does not trigger a post-back. For the list of regions to be
updated immediately, as the user modifies the Country field value, the OnLoad method
explicitly sets the AutoPostBack property of the country TextBox control to true . This trig-
gers a post-back when the user tabs out or clicks away from the text box after changing
the Country value.
Initial Implementation of the Region_Edit Field Template
Figure 10.5 shows a web page generated after the Customer entity template was modified
to use the Region field template.
FIGURE 10.5 Web page with custom Region field template.
The complete code-behind file of the Region_Edit field template is shown in Listing
10.15.
LISTING 10.15 Initial Implementation of the Region_Edit Field Template (Code-Behind)
using System;
using System.Collections.Specialized;
using System.Web.DynamicData;
using System.Web.UI;
namespace WebApplication.DynamicData.FieldTemplates
{