Question

The title says it all, really.

I’ve found theImage.GenerateEmptyAlternateText property on the ASP.NET Image control and now I’m wondering if there’s any difference in setting
<asp:Image GenerateEmptyAlternateText="True" /> and <asp:Image AlternateText="" />?

Answer 1

Turns out setting AlternateText=”” doesn’t work to set an empty alt text, if it set to an empty string, it gets omitted when the image HTML is rendered. To get alt=””, one has to use the GenerateEmptyAlternateText property.

See below from “Accessibility in Visual Studio 2010 and ASP.NET 4“

ASP.NET controls that render images omit the alt attribute in the
rendered HTML if you simply assign an empty string to the
AlternateText property. For example, suppose you add the following
ASP.NET Image control to a page:

<asp:Image ImageUrl="PageDivider.gif" AlternateText="" Runat="Server" />

In this case, the following HTML is rendered:

<img src="PageDivider.gif" />

Notice that the alt attribute has disappeared. This is the default
behavior of all ASP.NET control attributes. When you do not assign an
attribute a value, it is not rendered. Unfortunately, in this case, we
really want to render an empty string as the alt attribute value.

In order to make sure that HTML rendered for an ASP.NET Image control
includes alt=””, you must set the GenerateEmptyAlternateText property
to true.