MICROSOFT_PRESS_EBOOK_PROGRAMMING_WINDOWS_8_APPS_WITH_HTML_CSS_AND_JAVASCRIPT_PDF

FIGURE 4-10 A common data-binding scenario between a source data object and two target UI elements, involving
two direct bindings and one binding with a conversion function.
How these bindings actually behave at run time then depends on the particular direction of each
binding, which can be one of the following:
One-time: the value of the source property (possibly with conversion) is copied to the target
property at some point, after which there is no further relationship. This is what you automatically do
when passing variables to control constructors, for instance, or simply assigning target property values
using source properties. What’s useful here is to have a declarative means to make such assignments
directly in element attributes, as we’ll see.
One-way: the target object listens for change events on bound source properties so that it can
update itself with new values. This is typically used to update a UI element in response to underlying
changes in the data. Changes within the target element (like a UI control), however, are not reflected
back to the data itself (but can be sent elsewhere as with form submission, which could in turn update
the data through another channel).
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