Binding expression within curly braces are evaluated at time of initialization of control. You can consider them as simple eval expression which will be instantly evaluated at time of building of page.
All expressions in following sample are one time binding expressions.
Here is how it works,
Note: You must always use One Time Binding, that uses least memory. One Time binding will never refresh its data.
One Time Binding is also used to set native values in properties. For example, setting false to a boolean property can be tricky as "false" string literal is considered as true. Curley braces expressions are simply evaluated by eval function and the result is stored in the property. So "{ false }" evaluates to a proper Boolean False value.