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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

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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.

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

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

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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.

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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.

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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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