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Using the ListCollectionView with a deferred Filter method in WPF with C#
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| In a previous blog
I covered how to perform filtering using the
ListCollectionView class on a datagrid. What I noticed on the implementation
on a larger result set was a little lag in the response when characters were
being entered into the filter textbox. The way it was implemented was for
each character entered; perform a filter on the datagrid.
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| I started thinking that it would be better to start a filter a
few milliseconds after the user stopped entering the filter before performing
the filter. I think it is logical that a user would not want to filter on a
single character. |
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The first action I took was to create a DelayAction class.
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public class DelayAction : IDisposable
{
private Timer timer;
public static DelayAction Initialize(Action action)
{
if (action == null)
{
throw new
ArgumentNullException
("DeferredAction Initialize NULL excpetion");
}
return new DelayAction(action);
}
private DelayAction(Action action)
{
this.timer = new Timer(new TimerCallback(delegate
{
Application.Current.Dispatcher.Invoke(action);
}));
}
public void Wait(TimeSpan delay)
{
this.timer.Change(delay,
TimeSpan.FromMilliseconds(-1));
}
}
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| In the MainWindow.xaml.cs code-behind I will create an instance
of the Delayed class and call the Wait() method. The Wait() method is where
I will specific how much time to wait before executing the method I want to
delay. In this example it is the method which filters the datagrid based on user input. |
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private readonly TimeSpan filterDelay =
TimeSpan.FromMilliseconds(500);
private DelayAction delayedAction;
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| In the above code I also create a TimeSpan instance and set it
to 500 milliseconds. I will use the filterDelay as the parameter for the
Wait() method. |
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| The DelayAction class is implemented in the textbox TextChanged
event. Instead of calling the FilterIt() method immediately after each
TextChanged event, it will wait for the amount of time which is passed to
the Wait() method. |
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if (delayedAction == null)
{
delayedAction = DelayAction.Initialize(() => FilterIt());
}
delayedAction.Wait(filterDelay);
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| I think if you are going to implement a filtering capability then
you should implement this delay too. The response if better and the user will
be more satisfied. However, you need to recognize that this method only filters
what have been loaded into the local datagrid. If you need to implement a
FULL-TEXT search of the database, that is a whole other story. Both Oracle
and Microsoft SQL Server have solutions for this. My other articles covering
Lucene.Net can provide a solution for this too. |
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| Download the source |
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| Posts: 103 |
| Comments:
86 |
| Fundamentals:
13 |
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The sample code on this website is provided to illustrate a concept and should not be used in
applications or Web sites without proper professional consultation, as it may not illustrate
the safest coding practices. I assume no liability for incidental or consequential damages
should the sample code be used for purposes other than as intended.
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