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Create custom Expression for FilterDescriptor

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Yavor
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Yavor asked on 13 May 2010, 08:07 AM

I need to be able to filter the RadGridView based on a collection property on each item. Here is a sample to illustrate my case. Let’s suppose that each item in the grid is of type Person and each person has a collection property ScheduledMeetings. I need to apply some kind of filter that does the following:

People.Where(p => p. ScheduledMeetings.Contains(someMeeting))

which will return all people participating in the specified meeting.

The documentation samples all use the built-in CreateFilterExpression method of the FilterDescriptor class. So my first choice was to use the existing FilterDescriptor class in combination with FilterOperator.Contains but it seems that ‘Contains’ only works with strings and not with IEnumerable (even with FilterDescriptor.MemberType specified)!

 I suppose I need to implement some custom FilterDescriptor class inheriting from FilterDescriptorBase and then provide the Expression from the CreateFilterExpression override. But how do I create such expression?

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Stefan Dobrev
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answered on 13 May 2010, 08:27 AM
Hi Yavor,

You can use the PredicateFilterDescriptor used in this blog post.

Regards,
Stefan Dobrev
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Todor
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answered on 14 May 2010, 12:50 PM
Thanks Stefan,

The PredicateFilterDescriptor really helped. This approach allows for direct use of predicates instead of creating the expression tree indirectly with the CompositeFilterDescriptor which is extremely more flexible and powerful!!

The referenced blog entry is excelent as well! 
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Stefan Dobrev
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Todor
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