# z:Bind Used to DataBind to an *Expression*. If the *Expression* is just a property-name then it is equivalent to `Binding`\ A `z:Bind` automatically updates if any referenced properties notify they have changed #### Usage ```markup TargetProperty = { z:Bind [, Source=] } ``` #### Source property Just like a standard `Binding`, the *data-source* is the current *BindingContext*, unless `Source` is specified.\ If this *data-source* supports `INotifyPropertyChanged`, changes will be tracked. #### z:Bind Expressions

Sample Expression	Source	Notes
`{z:Bind Count}`	BindingContext	Bind to `Count`, same as `Binding`
`{z:Bind Count * 2}`	BindingContext	Bind to an expression that yields Count * 2
`{z:Bind '(Delta.X < 0.2) && (Delta.X > -0.2)' }`	BindingContext	True if (Delta.X < 0.2) && (Delta.X > -0.2)
`{z:Bind '(Delta.X LT 0.2) AND (Delta.X GT -0.2)' }`	BindingContext	As above, using aliases instead of escape-sequences
`{z:Bind (Count * 2) LT 10}`	BindingContext	True if (Count * 2) < 10
`{z:Bind Sin(Count / 25.0)}`	BindingContext	Calls a function (see below)
`{z:Bind 'Value LT 0.2', Source={x:Reference MySlider}}`	An Element called MySlider	True if `MySlider.Value` < 0.2

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