Accessibility in Blazor ComboBox Component

9 Dec 20225 minutes to read

The ComboBox component has been designed with the WAI-ARIA specifications in mind, and applies the WAI-ARIA roles, states, and properties along with keyboard support. This component is characterized
by complete keyboard interaction support and ARIA accessibility support that makes it easy for people who use assistive technologies (AT) or those who completely rely on keyboard navigation.

ARIA attributes

The ComboBox component uses the combobox role, and each list item has an option role. The following ARIA attributes denotes the ComboBox state:

Properties	Functionalities
aria-haspopup	Indicates whether the ComboBox input element has a popup list or not.
aria-expanded	Indicates whether the popup list has expanded or not.
aria-selected	Indicates the selected option.
aria-readonly	Indicates the readonly state of the ComboBox element.
aria-disabled	Indicates whether the ComboBox component is in a disabled state or not.
aria-activedescendent	This attribute holds the ID of the active list item to focus its descendant child element.
aria-owns	This attribute contains the ID of the popup list to indicate popup as a child element.
aria-autocomplete	This attribute contains the ‘both’ to a list of options shows and the currently selected suggestion also shows inline.

Keyboard interaction

You can use the following key shortcuts to access the ComboBox without interruptions:

Keyboard shortcuts	Actions
Arrow Down	Selects the first item in the ComboBox when no item is selected. Otherwise, selects the item next to the currently selected item.
Arrow Up	Selects the item previous to the currently selected one.
Page Down	Scrolls down to the next page and selects the first item when popup list opens.
Page Up	Scrolls up to the previous page and selects the first item when popup list opens.
Enter	Selects the focused item and popup list closes when it is in open state.
Tab	Focuses on the next TabIndex element on the page when the popup is closed. Otherwise, closes the popup list and remains the focus of the component.
Shift + tab	Focuses on the previous TabIndex element on the page when the popup is closed. Otherwise, closes the popup list and remains the focus of the component.
Alt + Down	Open the popup list
Alt + Up	Closes the popup list
Esc(Escape)	Closes the popup list when it is in an open state and the currently selected item remains the same.
Home	Cursor moves before the first character in input
End	Cursor moves next to the last character in input

NOTE

In the following sample, disable the ComboBox component using t keys.

@using Syncfusion.Blazor.DropDowns

<SfComboBox TValue="string" TItem="Country" @ref="ComboObj" Enabled="@enable" Placeholder="Select a country" @onkeypress="@(e => KeyPressed(e))" DataSource="@LocalData">
    <ComboBoxFieldSettings Value="Code" Text="Name"></ComboBoxFieldSettings>
</SfComboBox>

@code {

    public SfComboBox<string, Country> ComboObj;

    public bool enable { get; set; } = true;
    public class Country
    {
        public string Name { get; set; }
        public string Code { get; set; }
    }

    List<Country> LocalData = new List<Country> {
        new Country() { Name = "Australia", Code = "AU" },
        new Country() { Name = "Bermuda", Code = "BM" },
        new Country() { Name = "Canada", Code = "CA" },
        new Country() { Name = "Cameroon", Code = "CM" },
        new Country() { Name = "Denmark", Code = "DK" },
        new Country() { Name = "France", Code = "FR" },
        new Country() { Name = "Finland", Code = "FI" },
        new Country() { Name = "Germany", Code = "DE" },
        new Country() { Name = "Greenland", Code = "GL" },
        new Country() { Name = "Hong Kong", Code = "HK" },
    };

    public void KeyPressed(KeyboardEventArgs args)
    {
        if (args.Key == "t")
        {
            enable = false;
        }
    }
}