By default, the ShowIdem property is empty string, which indicates that it has no effect. The ShowIdem property allows you to customize how repetitive captions are displayed by replacing identical captions with an alternative display, such as a different text or symbol. This helps improve clarity and avoids confusion when multiple captions are the same. The CellValue property specifies the cell's value/caption to display. The FormatColumn property specifies the format to display the cells in the column.

For instance, 

• "", no effect (empty string)
• " ", indicates that a blank space is shown for identical captions
• "<fgcolor gray>&#12291;", displays the 〃 symbol (ditto mark or quote character) for repeated captions in gray (idem).

The following screenshots display the "ShipCountry" column both with and without the ShowItem property enabled:

compared with