Configuring Accessibility in ASP.NET

Configuring Accessibility

For example, many a user does not use a conventional mouse, and other users use screen readers to read the text on Web sites, rather than displaying it on a monitor.

Public Accessibility Guidelines:

W3C WCAG standard and US Government’s Section 508 Rehabilitation Act.

How ASP.NET Controls Support Accessibility

For example, login controls such as Login, ChangePassword, PasswordRecovery, and CreateUserWizard use text boxes with associated labels to help a user who uses a screen reader or who does not use a mouse.

Another way some ASP.NET controls support accessibility is by allowing users to skip link text. Screen readers typically read the text of links from the top to the bottom of a page, enabling users to choose a specific link. ASP.NET controls that include navigation links provide the SkipLinkText property, which is enabled by default and allows users to skip past the link text. The CreateUserWizard, Menu, SiteMapPath, TreeView, and Wizard controls each support skipping links.

<a href="#Menu1_SkipLink">

<img alt="Skip Navigation Links" src="/WebResource.axd?d=_9Q2Lm" width="0" height="0" />

</a>

… menu links …

<a id="Menu1_SkipLink"></a>

The simplest way to follow this best practice is to use one of the ASP.NET controls that provide the SkipLinkText property.

Improving Visual Accessibility:

1. Describe every image by providing alt text using the AlternateText property

You can also set the Image.DescriptionUrl property to specify an HTML page that further describes an image. If an image is not important, set the GenerateEmptyAlternateText property to True to cause screen readers to ignore it.

2. Use solid colors for background and use contrasting colors for text
3. Create a flexible page layout that scales correctly when text size is increased
4. Set the Table.Caption property to a description of the table:

Whether he or she wants to hear the contents of the table or skip past it.

5. Provide a way to identify column headers

Table t = new Table();

TableHeaderRow tr = new TableHeaderRow(); t.Rows.Add(tr);

tr.TableSection = TableRowSection.TableHeader; //TableFooter, TableBody

TableHeaderCell tc = new TableHeaderCell(); tr.Cells.Add(tc);

tc.AssociatedHeaderCellID = new string[] { "Column1" };

tc.Scope = TableHeaderScope.Column;

         

The Calendar, DetailsView, FormView, and GridView ASP.NET server controls render HTML tables with these features.

6. Avoid defining specific font sizes

Use heading tags (such as <H1> or <H3>) instead of font sizes to support the user’s formatting options.

7. Avoid requiring client scripts
8. Assistive technologies often cannot render client scripts, so you should use client script only for nonessential effects, such as mouse rollovers.

WCAG standards do not allow controls that require client scripts, so if you must comply with these standards, you should also avoid using the LinkButton, ImageButton, and Calendar controls.