<ComboBox x:Name="cbo1"
          IsEnabled="{Binding cbo1_IsEnabled}"
          HorizontalAlignment="Left"
          Margin="303,136,0,0"
          VerticalAlignment="Top"
          Width="120"/>

public static bool cbo1_IsEnabled = true;

public static void ControlsEnable()
{
    // Disable
    ViewModel.cbo1_IsEnabled = false;
}