Combine Generic ICollection Expression with an Any Accepting a Generic Predicate

Question

I'm trying to figure out how to combine the following Expressions:

Expression<Func<TParent, ICollection<TChild>>> childSelector = p => p.Children;

Expression<Func<TChild, bool>> childPredicate = c => c.NameLast.StartsWith("V");

var anyExpression = childSelector <------> .Any(childPredicate);

The "<------>" is the part I don't know what to do with. I'm using LINQKit, I just can't figure out how to combine these expressions.

Can someone give me a hand?

score 1 · Answer 1 · answered Jun 22 '11 at 19:57

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I'm not 100% clear on what you want anyExpression to be, but this is my best guess.

Expression<Func<TParent, bool>> anyExpression = p => p.Select(childselector).Any(childPredicate);

answered Jun 22 '11 at 19:57

juharr

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This may work in other cases, and I did actually try this. While it did build, it gave me an error at runtime regarding the variable "p" not being defined. Which made sense, with the way I was building the predicate in other places in my code. Thanks for your answer, hopefully it will help someone here. – Dylan Vester Jun 27 '11 at 13:00

score 0 · Answer 2 · answered Jun 22 '11 at 19:15

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you can do childselector(parent).Any(childPredicate) where parent is a TParent instance.

answered Jun 22 '11 at 19:15

Bas

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Thanks for the response, however, I won't have an instance of a parent until much later in the program execution. I'm trying to build an expression try across multiple classes, so I'm a few levels removed from the actual querying. – Dylan Vester Jun 22 '11 at 19:22

score 0 · Accepted Answer · edited May 23 '17 at 11:48

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I found the answer to my problem

childSelector.Combine(p => p.AsQueryable().Any<TEntity>(this.Predicate), true)

This is how the code turned out.

edited May 23 '17 at 11:48

Community

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answered Jun 22 '11 at 20:04

Dylan Vester

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Combine Generic ICollection Expression with an Any Accepting a Generic Predicate

3 Answers3