Displaying selected item of a wpf ComboBox in a messagebox

I have the following ComboBox in XAML Code

<ComboBox Name="angleComboBox" SelectionChanged="angleComboBox_SelectionChanged">
                    <ComboBoxItem>Degree</ComboBoxItem>
                    <ComboBoxItem>Radian</ComboBoxItem>
</ComboBox>

along with its following event handler below

private void angleComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
        {
            string selection = angleComboBox.SelectionBoxItem as string;
            MessageBox.Show(selection);
        }

What I am trying to do is get the messagebox to display whatever I am selecting in the combobox for example a messagebox display the word Degree when Degree is selected from the ComboBox. For some reason selecting Degree in the ComboBox yields and empty message box and selecting Radian yields a messagebox with the word Degree instead of Radians.