How do I filter a collection of objects

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3.71/5 (4 votes)

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I have a animal class. a herbivore class which inherits from animal and a elephant class which inherits from herbivore. I also have a carnivore class which inherits from animal and a tiger class which inherits from carnivore. I Have a observable collection called zoo with tigers and elephants. I have a listbox hooked up to the zoo collection. How do I filter for example when a button in clicked just to show tigers or eg to show elephants.

This is the code where I bind the zoo collection to the listbox:

C#

lstBoxAnimals.ItemsSource = zoo;

Posted 4-Mar-14 5:34am

Member 10642704

Updated 4-Mar-14 5:56am

Thomas Daniels

v2

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Comments

Sergey Alexandrovich Kryukov 4-Mar-14 11:38am

It depends on what you want to do, exactly.
—SA

Maciej Los 4-Mar-14 15:02pm

Agree. I had tried to explain it in my answer. I'm interesting of your opinion. What you think about it?

Sergey Alexandrovich Kryukov 4-Mar-14 15:14pm

I think this is one of constructive approaches to helping with such vague questions. You can either try to pull some clarification from OP, or provide some general information with the set of some useful links. We all understand that OP cannot get any pin-pointing advice, but showing where to look at and what is the problem with such questions can help to start moving in right direction.
—SA

BillWoodruff 4-Mar-14 21:41pm

What the OP wants to do is crystal clear: filter a Collection used as a DataSource.

Sergey Alexandrovich Kryukov 4-Mar-14 21:46pm

Well, this part I understand, too... :-)
—SA

Sergey Alexandrovich Kryukov 4-Mar-14 22:12pm

Also, for the very first time I read the OP's post with attention. It does not worth helping, by the reason I explained in my answer. Don't tell me I'm overreacting; I take such things seriously...
—SA

Thomas Daniels 4-Mar-14 11:39am

Can you show the code where you bind the zoo collection to the listbox?

Maciej Los 4-Mar-14 11:49am

Do you mean filter or search for items in ObservableCollection<T>?

Member 10642704 4-Mar-14 11:51am

I want to filter between herbivores and carnivores or a button click for example

Maciej Los 4-Mar-14 12:31pm

Please, improve your question and post the declaration of zoo (observablecollection).

Sergey Alexandrovich Kryukov 4-Mar-14 22:11pm

Okay, for the very first time I read the OP's post with attention. It does not worth helping, by the reason I explained in my answer. Don't tell me I'm overreacting; I take such things seriously...
—SA

2 solutions

Solution 2

I have no idea what you mean by "How do i filter a collection of objects". You did not provide enough information about your issue, even if you've been asked for it.

I would suggest to read this: Sorts and filters on ObservableCollection[^]. The author of above article wrote that ObservableCollection<T> allow sorting and filtering operations via CollectionViews[^]. I've never used that, but i think it's quite good idea.

I think below set of articles might be interesting too:
Give Your Everyday Custom Collections a Design-Time Makeover[^]
Collections (C# and Visual Basic)[^]

But the most powerful tool is Linq[^]:
How to: Populate Object Collections from Multiple Sources (LINQ)[^]
Using Observable collection with linq[^]

Try! And come back here with detailed question.
Cheers,
Maciej

Posted 4-Mar-14 8:42am

Maciej Los

Comments

Sergey Alexandrovich Kryukov 4-Mar-14 15:11pm

At the very least, it can give OP the idea on what's involved. My 5.
Actually, the problem is not correctly formulated by OP; it remains unclear how the collections should be used, why, what's the goal of filtering, etc.
—SA

Maciej Los 4-Mar-14 15:18pm

Thank you, Sergey for both comments ;) I really appreciate your opinion.

BillWoodruff 4-Mar-14 21:44pm

My vote of #3: What the OP wants to do is extremely easy to understand, and the solution is very easy to write.

Maciej Los 5-Mar-14 2:00am

Bill, don't you think your opinion is bit unfair (3 stars means down-voting)? I have done everything to make question more clearly (see my comment to the question). My answer is at least good, because provides a ways to find solution. I really appreciate your opinion, but i disagree with it ;(

BillWoodruff 9-Mar-14 7:17am

Maciej, I personally do not consider a vote of #3 a down-vote, but, rather, a neutral vote that acknowledges that effort, and helpful intent, went into the post. But, I think, given the richness of your response, I should change that to a #4, and I have. cheers, Bill

Maciej Los 9-Mar-14 7:39am

Bill, thank you for explonation. I would like to confirm that 3 stars means down-voting. Please check reputation FAQ.
Thank you, Bill ;)
Cheers!
Maciej

BillWoodruff 9-Mar-14 8:23am

Hi Maciej, You've got me curious, and I just read the QA FAQ, and the CP FAQ. I can't find any mention that a #3 is a down-vote on QA. I'm going to post a question about that on the Help Forum, since I certainly do not wish to inadvertently down-vote anyone ! thanks, Bill

posted:

http://www.codeproject.com/Questions/741182/Is-a-vote-of-sharp-on-a-QA-post-a-down-vote

Maciej Los 9-Mar-14 15:28pm

Very interesting discussion ;)

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BillWoodruff · Accepted Answer · 2014-03-04T15:40:00

This is quite easy to do: assuming your ObservableCollection<Animal> is named 'ZooAnimals' and your ListBox is named 'TheZoo' .. and there are two buttons with Click EventHandlers:

C#

private void TigersOnly_Click(object sender, EventArgs e)
{
    // filter ListBox to only show Tigers
    TheZoo.DataSource = ZooAnimals.Where(tgr => tgr is Tiger).ToList();

    // an alternative
    // TheZoo.DataSource = ZooAnimals.OfType<Tiger>().ToList();
}

private void ElephantsOnly_Click(object sender, EventArgs e)
{
    // filter ListBox to only show Elephants
    TheZoo.DataSource = ZooAnimals.Where(elp => elp is Elephant).ToList();

    // an alternative
    // TheZoo.DataSource = ZooAnimals.OfType<Elephant>().ToList();
}

Of course, you can reset the ListBox to show all instances of Types derived from Animal/Whatever-Vore/ by simply setting: TheZoo.DataSource = ZooAnimals;

Welcome to CodeProject :)