Databases Reference
In-Depth Information
public class FilterFactory
{
public FilterFactory();
public virtual QueryableFilterUserControl
CreateFilterControl
(
MetaColumn column, string filterUIHint);
public virtual string
GetFilterVirtualPath
(
MetaColumn column, string filterUIHint);
}
The
GetFilterVirtualPath
method is responsible for determining a virtual path to
a filter template, such as
~\DynamicData\Filters\Text.ascx
, that matches the given
MetaColumn
object and
filterUIHint
.
The column contains metadata information
describing the entity property, and the filter hint comes from the page markup. The
CreateFilterControl
is invoked by the
DynamicFilter
(or, in our case, the
UnleashedFilter
) control to create an instance of the filter template. Internally, the
CreateFilterControl
calls the
GetFilterVirtualPath
method and caches its results to
improve performance for subsequent lookups of the same column and hint combination.
Therefore, you need to override only the
GetFilterVirtualPath
method and can leave the
CreateFilterControl
method as is.
Listing 13.1 shows the complete implementation of
UnleashedFilterFactory
, a class that
extends the built-in
FilterFactory
to implement fallback-based algorithm for filter
template lookup. As you can see, it overrides the
GetFilterVirtualPath
method just
discussed; however, most of the heavy lifting is actually done by the
GetFilterCandidates
method. This method returns an
IEnumerable
of strings where each item is a
possible
name of the filter template, based on the given
MetaColumn
and filter hint. The
GetFilterVirtualPath
method tries the candidate names until it finds an existing .ASCX
file in the
DynamicData\Filters
folder of the project. If none of the candidate names
matches an existing filter template, the
GetFilterVirtualPath
calls the base method,
inherited from the
FilterFactory
, to handle the Boolean, ForeignKey, and Enumeration
filter templates it supports.
LISTING 13.1
UnleashedFilterFactory Implementation
using System;
using System.Collections.Generic;
using System.Web;
using System.Web.Compilation;
using System.Web.DynamicData;
namespace Unleashed.DynamicData
{
public class UnleashedFilterFactory : FilterFactory
{
private static readonly Dictionary<Type, Type>
FallbackTypes
=
new Dictionary<Type, Type>
{
