Provides an identifier within markup elements that is used by localization processes and tools.
x:Uid is the singular exceptional case in Extensible Application Markup Language (XAML) where an attribute is permitted to be on a property element. All other attributes are invalid on a property element. This usage is necessary because a property element can still contain a string, and the only way to mark that string to be a unique resource that needs to be localized is to place the x:Uid attribute on the enclosing property element.
Custom Extensible Application Markup Language (XAML) processors must not raise an error condition if they encounter x:Uid on a property element.
Extensible Application Markup Language (XAML) processors in the generic sense (processors that are not necessarily part of the localization process) are not expected to enforce uniqueness of x:Uid values. That responsibility is on the originator of the values, and the expectation of uniqueness is reasonable for consumers of the values, such as dedicated globalization processes or tools.