By default, the FormatImage property is empty (it indicates that no icons is being displayed). The FormatImage property defines the expression to determine the images the column display. Use the Images method to insert icons at runtime. Use the ReplaceIcon method to add, remove or clear icons in the control's images collection. The FormatImage expression should return an integer value that specifies the index of the icon to displayed (zero indicates that the column displays no icons). The expression may be a combination of variables, constants, strings, dates and operators, and value. The value operator gives the value of the cell to display the icon.

For instance:

• "" or "0",  no icons is being shown within the column 
• "1", displays the icon with the index 1 (first icon) for the entire column 
• ""1 pos `` mod 2 ? 1 : -1"" , displays alternate icons
• "%1 = 'NM' ? 1 : 0", display the first icon for all values NM within the column with the index 1
• "value case (default: -1;'Germany': 1;'USA': 2;'Mexico': 3)", displays the icon with the index 1 for Germany, the icon with the index 2 for USA, the icon with the index 3 for Mexico, and empty icon for every other value.

The value keyword in the FormatColumn property indicates the value of the cell. 

The expression supports cell's identifiers as follows:

• %0, %1, %2, ... specifies the value of the cell in the column with the index 0, 1 2, ...

This property/method supports predefined constants and operators/functions as described here.

The following screen shot shows the control with icons:

The following screen shot shows the control with no icons: