The CSSClass property points to a specific class in a CSS file. You can use individual CSS classes to set fonts and colors for forms as well as groups of controls. Use with the CSSName property.

Applies to: Forms and all controls except grids and menu.

Setting dynamically:

Winform Show_inactive form 
Winform Set form.CSSClass TO 'classname'; 
Winform Show form

Property Settings:

Enter the name of the CSS class within a CSS file, and provide the CSS file name in the CSSName property. The CSS file must be included in the project during the development process and assigned to a web server when deployed.

For more information, see the CSSName property.