To resize rows or columns, the mouse must be over the fixed area of the grid, and close to a border between rows or columns. The mouse pointer will change into a sizing pointer and the user can drag the row or column to change the row height or column width.

If a group of columns is selected (from first to last row) and the user resizes one of them, all selected columns are resized. The same applies to rows.

If column sizing is allowed, users may double-click the resizing area to resize a column so it will automatically fit the longest entry.

Rows with zero height and columns with zero width can't be resized by the user. If you want to make them very small but still resizable, set their height or width to one pixel, not to zero.

The C1FlexGridBase.BeforeResizeRow and C1FlexGridBase.BeforeResizeColumn events fire before resizing starts, and may be used to prevent resizing of specific rows and columns. The C1FlexGridBase.AfterResizeRow and C1FlexGridBase.AfterResizeColumn events fire after resizing, and may be used to validate the user's action and to update the display.

Reference

C1FlexGrid Class
C1FlexGrid Members