This method is called when the user presses ALT+0 to allow a column to enter the appropriate null value. For example, when called on a DataGridTextBoxColumn, the appropriate NullText value is inserted into the column.
The EnterNullValue has no default behavior. When inheriting from DataGridColumnStyle, override the method to enter null in a column.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)