Databases Reference
In-Depth Information
required to filter child entities based on the parent property value. In the following two
sections,
Initializing Nested Filter Control
and
Implementing Query Logic
, you get a close look
at the internals of this filter control. Based on this example, some of the more challenging
aspects of advanced filter template design are discussed. However, you can also skip them
and continue reading the section
Using the Parent Filter Template
later in the chapter
.
Initializing Nested Filter Control
The filter control needs an
IQueryableDataSource
object (an
EntityDataSource
or a
LinqDataSource
), a
MetaTable
describing the target entity, and a name of the target entity
property. Listing 12.8 shows the part of ParentFilter implementation responsible for the
initialization.
LISTING 12.8
Parent Filter Template (Initialization Logic)
using System;
using System.Linq;
using System.Linq.Expressions;
using System.Web.DynamicData;
using System.Web.UI.WebControls;
namespace WebApplication.DynamicData.Filters
{
public partial class ParentFilter : UnleashedFilterTemplate
{
private object dataSourceContext;
public string DisplayField { get; set; }
protected void Filter_Init(object sender, EventArgs args)
{
this.filter.DataSource = this.DataSource;
this.filter.Table = this.ForeignKeyColumn.ParentTable;
this.filter.DataField = this.DisplayField;
((EntityDataSource)this.DataSource).ContextCreated +=
this.DataSourceContextCreated;
((EntityDataSource)this.DataSource).Selecting += this.DataSourceSelecting;
}
private void DataSourceContextCreated(object sender,
EntityDataSourceContextCreatedEventArgs e)
{
this.dataSourceContext = e.Context;
}
private void DataSourceSelecting(object sender,
