Building Dynamic Forms - ASP.NET Dynamic Data - page 371

an open-ended array as its last argument, so if you needed to specify additional control
parameters, you would simply add more names and values to this list.
NOTE
Specifying “WebForms” as the presentation layer in the UIHintAttribute constructor
is only required when you need separate UIHint annotations for different presentation
frameworks, such as MVC and WebForms, for the same property. In that case, Dynamic
Data picks the UIHint where the presentation layer is specified as “WebForms”.
Otherwise, it uses the UIHint for “MVC” or the one where the presentation layer is not
specified. If you are not planning to use UIHint annotations with multiple platforms,
leaving it null might be the best option.
Unfortunately, the built-in DynamicControl does not support custom control parameters
specified in the UIHintAttribute the way it supports its own custom attributes specified
in markup. However, you can easily work around this limitation by extending the
dynamic entity templates. As discussed in Chapter 4, “Entity Templates,” and later in
Chapter 10, the dynamic entity templates rely on the Init event handler to initialize each
DynamicControl it creates. Extending this event handler is the simplest way to implement
support for custom parameters. Here is how you can extend the Init event handler imple-
mented in Default.ascx.cs , the code-behind file of the combined entity template created
in Chapter 10:
protected void DynamicControl_Init(object sender, EventArgs e)
{
var dynamicControl = (DynamicControl)sender;
dynamicControl.DataField = this.currentColumn.Name;
dynamicControl.Mode = this.Mode;
dynamicControl.ValidationGroup = this.ValidationGroup;
var hint = this.currentColumn.Attributes.OfType<UIHintAttribute>()
.FirstOrDefault();
if (hint != null)
{
foreach (KeyValuePair<string, object> p in hint.ControlParameters)
dynamicControl.SetAttribute(p.Key, p.Value.ToString());
}
}
The new code (indicated by bold font) tries to find a UIHintAttribute applied to the
current column (a MetaColumn object describing an entity property for which a field
template needs to be created). If the attribute was found, it uses the names and values in
the ControlParameters dictionary to set custom attributes for the DynamicControl . The
DynamicControl , which has not created the field template yet, takes care of the rest and