Posts Tagged ‘WPF’

WPF: Setting a Type Specific Property Value

August 7th, 2009

While XAML in WPF is probably the most powerful GUI development architecture I’ve ever used and by far my favorite, there’s still a few little tasks here and there that I just scratch my head trying to figure out.

This is probably due to my limited knowledge of XAML and how to use it properly, so until I get it all mastered I’m forced to use lines of DuctTape to get some of the results I want.

Here’s my most recent hack job. If you look at the XAML below you’ll notice that I’m making use of the Tag property of the button. This is just an example, but in real life there’s actually quite a few valuable uses for Tag.

<Button Content="Am I the right button?" Tag="False" Click="Button_Click" />
<Button Content="Am I the right button?" Tag="True" Click="Button_Click" />
<Button Content="Am I the right button?" Tag="False" Click="Button_Click" />

So in this example the user needs to click the right button. The right button is indicated by its tag property. In this case the second button is the one that works, right?

Which button is it?

Not exactly.

The code to handle this situation would look something like ths:

private void Button_Click(object sender, RoutedEventArgs e)
    var sourceBtn = sender as Button;
    bool isRight = (bool)sourceBtn.Tag;

Since Tag is defined as an object and I’m binding it to “False” in my XAML I thought this code would work out just fine, but it doesn’t.

The problem is Tag gets populated with a string instead of a boolean. That’s interesting, after all why shouldn’t it? How is XAML supposed to know that what I wanted to set to Tag is the boolean value False? It doesn’t.

So I had to write my XAML in such a way that it knew without a doubt that I was using a boolean value.

The first thing in accomplishing this was to include the System namespace in my XAML file, like so:


Then I could declare my Tag property full out giving it a system:Boolean for its value.

<Button Content="Am I the right button?" Click="Button_Click">
<Button Content="Am I the right button?" Click="Button_Click">
<Button Content="Am I the right button?" Click="Button_Click">

And that’s it, it works! Yay!

But man, it really is ugly. Does anyone know of a cleaner, better way to accomplish the same thing? I would love to learn something new!

WPF: Bind Control Enabled to Checkbox Checked

July 23rd, 2009

This is a simple example of a nifty use of binding in WPF.

Say you have an element in your application such as a TextBox, ComboBox, or some RadioButtons that you want to keep disabled to the user unless the user checks a box. You may even want to disable a whole section of controls contained inside of a StackPanel or DockPanel.

Everything enabled

To accomplish this you bind the IsEnabled property of the target control (in this case a ComboBox) to the IsChecked property of the CheckBox.


    <CheckBox x:Name="chkEnableBackup">Run Backup Sets</CheckBox>
    <StackPanel Orientation="Horizontal">
        <Label Margin="12,0,0,0">Run backup every</Label>
        <ComboBox Width="70" SelectedIndex="0"
          IsEnabled="{Binding ElementName=chkEnableBackup, Path=IsChecked}">

That’s it! Our result is that when the box is not checked the control is disabled.

Control disabled!

WPF: Center Child Window

May 7th, 2009

Here’s a method I’ve found for centering a window to either its parent or the main window for the application, in WPF. It’s not too far different from how you do it in WinForms.

For the child window set it’s WindowStartupLocation to “CenterOwner.” This will cause it to show in the center of the owning Window.

<Window x:Class="WpfApplication1.TestChild"
    Title="TestChild" Height="300" Width="300"

Now all that’s left to do is set its owner before displaying it. If the code you’re using to display the window is running inside of a Window class, then you can just use this.

TestChild testWindow = new TestChild();
testWindow.Owner = this;

This isn’t always the case however, sometimes you need to display the child window from code running on a page or a user control. In this case you want the child window to be centered to the main window of the application.

TestChild testWindow = new TestChild();
testWindow.Owner = Application.Current.MainWindow;

WPF: Vista Blue Highlight Brush

April 17th, 2009

For the WPF application I’m currently working on for work I decided that I wanted to change the style for all ListBoxItems so that they looked a little more like list items in Vista when highlighted, instead of the boring white text on a black background.

So I found this wonderful guide to setting the style for IsSelected ListBoxItems across the application. You can find it here:

Then, for a nice light-blue, glossy vista look I used this gradient:

<LinearGradientBrush StartPoint="0,0" EndPoint="0,1">
        <GradientStop Offset="0" Color="#FFE3F4FC"/>
        <GradientStop Offset="0.38" Color="#FFD8EFFC"/>
        <GradientStop Offset="0.38" Color="#FFBEE6FD"/>
        <GradientStop Offset="1" Color="#FFA6D9F4"/>

It’s not perfect, but it looks pretty good. I also gave it a solid LightBlue border with a corner radius of 5. Here’s what the results looked like:
Vista Blue Highlight