Gets the actual width of a GridViewColumn.
Assembly: PresentationFramework (in PresentationFramework.dll)
You can use this property to get the current width of the GridViewColumn when the Width property is set to Double::NaN. A value of Double::NaN for the Width property specifies that the column size accommodate the largest visible item that is not the column header.
Unlike FrameworkElement::ActualWidth, is not a dependency property.