This property value is being kept in sync with a number of items in the System.Windows.Controls.Grid.ColumnDefinitions collection.
If a number of items in the System.Windows.Controls.Grid.ColumnDefinitions collection has been changed then the value of the AutoDistributionGrid.ColumnCount property is updated automatically.
If a value of the AutoDistributionGrid.ColumnCount property is changed directly, then items will be added or removed to/from the end of System.Windows.Controls.Grid.ColumnDefinitions collection until its number becomes equal to the new AutoDistributionGrid.ColumnCount value.