You can get or set a CSS class name to add to the controls drop-down element. The property is useful when you are styling the drop-down element, because it is shown as a child of the document body rather than as a child of the control itself, which prevents using CSS selectors based on the parent control. You can use this property to display multiple columns in a ComboBox dropdown.

The following code example demonstrates how to enable multi-column using DropDownCssClass property. This example uses the sample created in the Quick Start section.

DropDownCssClass property is available in the following Input DropDown controls;

• InputColor
• InputDate
• AutoComplete, ComboBox
• InputTime
• MultiSelect
• Menu

The following image shows how the Menu appears after applying the DropDownCssClass property:
The following code example demonstrates how to use DropDownCssClass property.

IndexController.cs

public ActionResult Index()
        {
        ViewBag.Cities = Models.Cities.GetCities();
        return View();
        }

ComboBox.cshtml

<style>
    .multi-column
    {   display: flex;
        flex-wrap: wrap;
        max-width: 450px;
    }
</style>
@{ List<string> cities = ViewBag.Cities;}
   <c1-combo-box selected-index="0" is-editable="false" drop-down-css-class="multi-column"> 
    <c1-items-source source-collection="cities"></c1-items-source> 
</c1-combo-box>