Question

Am i missing something here? I have created a usercontrol with a property and for arguments sake it has a text box in it.

<UserControl x:Class="Isd.Utility.SystemMonitorWpf.Bar"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">

<TextBlock x:Name="txtExpected" Grid.Column="0" Grid.ColumnSpan="2" Width="auto" Height="auto" FontSize="10" LayoutTransform="{StaticResource Rotate}" HorizontalAlignment="Center" VerticalAlignment="Center" FontFamily="Tahoma" Foreground="Red" Panel.ZIndex="100" Margin="5,5,5,5"/>

Then in the code behind i have

public partial class Bar : UserControl
{
    private string _PropTest;

    public string PropTest
    {
        get { return _PropTest; }
        set { _PropTest = value; }
    } 

public Bar()
    {
        InitializeComponent();
        txtExpected.Text = PropTest;
    }
}

Then i drop the usercontrol into the xaml and set the property to a value

<local:Bar PropTest="test"></local:Bar>

In this example, when the usercontrol is displayed the text is showing as null, its like the property PropTest never got set. Am I missing something obvious here? Thanks in advance.

Answer 1

You don’t appear to be doing anything in the setter of PropTest. It won’t be set prior to construction, so it will be null when you do:

txtExpected.Text = PropTest;

Inside your constructor. If you do this:

public string PropTest
{
    get { return _PropTest; }
    set 
    { 
        _PropTest = value; 
        txtExpected.Text = PropTest;
    }
} 

It should work. It’s not what I’d call an “ideal” way to do things though, you might want to take a look at Dependency Properties, INotifyPropertyChanged and Binding.