Databases Reference
In-Depth Information
example shows how this can implemented by overriding the
OnLoad
of the field
template:
private FieldTemplateUserControl countryFieldTemplate;
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
this.countryFieldTemplate = this.
FindOtherFieldTemplate
(“Country”);
}
Having located the field template instance of the Country property, you can use it to
access the property value and store the country name in the
ContextKey
of the
AutoCompleteExtender
, which will pass it to the
GetCompletionList
of the
RegionCompletionService. This needs to be done during the Data Binding stage of the
field template lifecycle when the Customer entity instance has already been retrieved from
the database during the Load stage. The next code example shows how this can be imple-
mented in the overridden
OnDataBinding
method:
protected override void OnDataBinding(EventArgs e)
{
base.OnDataBinding(e);
string country = this.countryFieldTemplate.FieldValueEditString;
this.autoCompleteExtender.ContextKey = country;
}
Accessing Modified Field Values of Other Columns
At this point, the Region field template can display the list of regions appropriate for the
current country when the web page is first rendered for an existing Customer entity
instance. However, when the field template is used in Insert mode and the customer
entity does not exist, the country name has not been entered yet, and the list of regions
will be empty. The list will also not be updated when user changes the
Country
value from
its initial value. So the last challenge is to figure out how to reload the list of regions as
the
Country
property value changes.
Just like in a traditional ASP.NET application, you can use post-backs and event handlers
to implement code that reacts to user input. The custom
Region
field template needs to
respond to the change made by the user in the
Country
field template, which requires
accessing the
TextBox
control it instantiates. The next example shows an extract from the
Region_Edit field template that accomplishes this task:
protected override void OnLoad(EventArgs e)
{
base.OnLoad(e);
var countryFieldTemplate = this.FindOtherFieldTemplate(“Country”);
var countryTextBox = (TextBox)countryFieldTemplate.DataControl;
countryTextBox.AutoPostBack = true;
