Binding ComboBox SelectedIndex to Method in wpf

hello guys

How can I binding a method from class to ComboBox SelectedIndex?

This is my method in a class:

    public static class myClass
    {
        private static int tempComboIndex = 0;
        public static int ComboIndex
        {
            get { return tempComboIndex ; }
            set { tempComboIndex = value; }
        }
    }

And I've tried this xaml code to binding:

<ComboBox SelectedIndex="{Binding Path=myClass.ThemeIndex,Mode=TwoWay}">
<ComboBoxItem Content="1"/>
<ComboBoxItem Content="2"/>
</ComboBox>

:)