WPF Set user control dependency properties

Below a piece of my user control:

<UserControl x:Class="WpfApplication1.Controls.CircularProgressBar"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             Background="Transparent"
             Height="{Binding ControlHeightProperty}"
             Width="{Binding ControlWidthProperty}">

  <UserControl.Resources>
    <SolidColorBrush x:Key="progressCirclesColor" Color="#FF2E6187" />
  </UserControl.Resources>

    <Viewbox Width="{Binding ControlWidthProperty}" Height="{Binding ControlHeightProperty}" HorizontalAlignment="Center" VerticalAlignment="Center">
    <!-- other objects -->
    </Viewbox>
</UserControl>

and its code-behind with my dependency properties:

public partial class CircularProgressBar
{
    public static readonly DependencyProperty ControlHeightProperty =
        DependencyProperty.Register("ControlHeight", typeof(int), typeof(CircularProgressBar), new UIPropertyMetadata(45));

    public static readonly DependencyProperty ControlWidthProperty =
        DependencyProperty.Register("ControlWidth", typeof(int), typeof(CircularProgressBar), new UIPropertyMetadata(45));

    public int ControlHeight
    {
        get { return (int)GetValue(ControlHeightProperty); }
        set { SetValue(ControlHeightProperty, value); }
    }

    public int ControlWidth
    {
        get { return (int)GetValue(ControlWidthProperty); }
        set { SetValue(ControlWidthProperty, value); }
    }
}

Then from my wpf main window:

    <ctr:CircularProgressBar x:Name="progressBar" Grid.ZIndex="3"                             
                         HorizontalAlignment="Center"
                         VerticalAlignment="Center"
                         ControlHeight="100"
                         ControlWidth="100"/>   

What I am trying to do is set width and height for my user control from my main window. In above example I am trying to set user control height and width to 100 through dependency properties ControlHeight and ControlWidth respectively.

If from my main windows ControlHeight and ControlWidth is not specified, I want user control height and width take as default value of 45.

But above example is not working for me. What am I doing wrong?

UPDATE WORKING: As Clemens suggested, I have changed the code into the following:

<UserControl x:Class="WpfApplication1.Controls.CircularProgressBar"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             Background="Transparent">

  <UserControl.Resources>
    <SolidColorBrush x:Key="progressCirclesColor" Color="#FF2E6187" />
  </UserControl.Resources>

    <Viewbox HorizontalAlignment="Center" VerticalAlignment="Center">
    <!-- other objects -->
    </Viewbox>
</UserControl>

In code-behind dependency properties ControlHeightProperty and ControlWidthProperty are not needed.

Finally in my wpf window, setting typical height and width properties are enough:

    <ctr:CircularProgressBar x:Name="progressBar" Grid.ZIndex="3"                             
                         HorizontalAlignment="Center"
                         VerticalAlignment="Center"
                         Height="100"
                         Width="100"/>