When the NavigationPaneExpansionThreshold property is set to a specific, non-default value, the NavigationPaneExpansionThresholdResolved returns that same value. When the NavigationPaneExpansionThreshold property is left at its default value, the control uses a "best fit" value for the actual threshold; in that case, the NavigationPaneExpansionThresholdResolved returns this value. The "best fit" value is based on the size of the images which are displayed by the group headers; when the control's UseLargeGroupHeaderImagesResolved property returns true, this size is based on the ImageSizeLarge property, and when UseLargeGroupHeaderImagesResolved returns false, it is based on the ImageSizeSmall property.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2