How to: Sort the Contents of a Windows Forms ComboBox, ListBox, or CheckedListBox Control
Windows Forms controls do not sort when they are data-bound. To display sorted data, use a data source that supports sorting and then have the data source sort it. Data sources that support sorting are data views, data view managers, and sorted arrays.
If the control is not data-bound, you can sort it.
To sort the list
Set the Sorted property to true.
This setting repositions all existing list items in sorted order.
See Also
Tasks
How to: Add and Remove Items from a Windows Forms ComboBox, ListBox, or CheckedListBox Control
Reference
Concepts
When to Use a Windows Forms ComboBox Instead of a ListBox