XAML and local variable/auto property...

Question

Hi all,
I try to set a local property through XAML and a trigger.
The idea is to "reproduce" the behaviour that exists in most of settings pages with an "Apply" button at the bottom.
As soon as the user modify one the the control/settings in the page, I want to set a local variable ("FilterModified") to "true".
I tried this, but somehow, I cannot get it to compile:

<ToggleButton.Triggers>
    <Trigger Property="ToggleButton.IsChecked">
        <Setter Property="myUserControl.FilterModified" Value="True"/>
    </Trigger>
</ToggleButton.Triggers>

In the code, FilterModified is declare like this:

public partial class myUserControl: UserControl
{
    public static Boolean FilterModified { get; set; }

Could someone please help me?
Thx in advance.
Fred

Answer 1

It would help if you posted the compile error you're getting, but I suspect you need to make FilterModified a dependency property instead of a regular one. The easiest way is to type propdp in Visual Studio, press Tab and set the highlighted fields to the correct values:

public bool FilterModified
{
    get { return (bool)GetValue(FilterModifiedProperty); }
    set { SetValue(FilterModifiedProperty, value); }
}

// Using a DependencyProperty as the backing store for FilterModified.  This enables animation, styling, binding, etc...
public static readonly DependencyProperty FilterModifiedProperty =
        DependencyProperty.Register("FilterModified", typeof(bool), typeof(ownerclass), new UIPropertyMetadata(false));

With this the XAML you posted should work, I think.

Edit: however, of course, I'd suggest looking into MVVM (Model-View-ViewModel) for doing things like this, and leaving only the bindings do the heavy lifting; that would mean moving the FilterModified into the ViewModel and handling it only from there, instead of from the code-behind which is tied to that exact control.

Answer 2

Thx Alex Paven for the answer.
Is it so "complicated"? What I need is really trivial.
I could implement the 'Check' and 'Uncheck' event, but I'm sure, it should be possible to do it with XAML.
I changed the 'Setter' line to

<Setter TargetName="local:myUserControl.FilterModified" Value="True"/>

Now it compiles, but the Designer complains with:

"Error    5    Value 'True' cannot be assigned to property 'Value'. Object reference not set to an instance of an object."

If I put this:

<Setter Property="{x:Static local:myUserControl.FilterModified}" Value="True"/>

It compiles too, but the Designer says:

Error    4    Property 'Property' does not support values of type 'Boolean'.

Very strange, isn't it?

Fred