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How to determine if a dependency property has been explicitly set?

Posted By:      Posted Date: April 10, 2011    Points: 0   Category :JavaScript/VBScript




I am currently developing a custom activity library. Some of my activities expose a set of interger type dependency properties. Zero would be a valid value for these properties - but only if it has been explicity set.


I want to write validation logic in an activity validator along the lines of:


.. if there is not explict value set then ensure that the property is bound



And also when the activity executes and want to use the value of the property (including zero) - but only if the value was explicitly set or passed through the binding.


I am having problems because the property value is default initialized to zero (if set or not). I have tried defining my dependency property as nullable types but this seems to lead to null reference exceptions in visual studio.


Has anyone else addressed this problem?

Are dependency properties intendend to support nullable types and so should I continue with this?

Is there any built in way to determine if a dependency property value has been explicitly set at design time?



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