Added category interfaces to BUTTON, INPUT, SELECT, LABEL, and SELECT.

[joelverhagen]

See the HTML 5 spec Forms page for more information. To determine in an element has an associated form, it is as easy as:

IDomElement e = doc["some selector"].FirstElement();
IFormAssociatedElement f = e as IFormAssociatedElement;

if(f != null)
    ...

Also:

• Added Disabled property to IDomObject, much like ReadOnly and Checked.
• Added correct implementations of Disabled to form fields that can be disabled by a FIELDSET.
• Tests for new product code.

[jamietre]

I would like to merge this, but don't have time to look at it carefully anytime soon, can you explain the purpose of the interfaces IFormSubmittableElement, IFormReassociatableElement? Are these just markers for convenience of end users?

[joelverhagen]

IFormSubmittableElement: this interface indicates that the element should be included in the data set generated when submitting the associated form.

IFormReassociatableElement: this interface indicates that the element can be associated with a non-ancestor form using the form attribute.

Yes, the interfaces themselves serve as convenience markers on elements. However, the associated abstract classes (FormSubmittableElement and FormReassociateableElement) do provide special functionality shared by all elements implementing this interface. You'll notice any element implementing these interfaces is doing so through inheritance of the associated abstract class.

In general, I hope these pull requests make working with form fields both more generic (e.g. only implement Disabled once for form fields) and more staticly typed (via the IHTML* interfaces).