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POC# Class library collections ObservableCollection<T> vs Collection<T>
 

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    <p>I'm creating a class library that could be used in a number of situations ASP.NET, Console Apps, other class libraries and XAML targets like Silverlight or WPF.</p> <p>Initially I decided to expose collections as IList. But then when writing samples using XAML I found that if I want to make it easy to bind to these collections I need to use ObservableCollection.</p> <p>What are my options?</p> <p>I could make the library expose ObservableCollection and force that upon users who have nothing to do with XAML. Is that a bad thing?</p> <p>I could make my class generic allowing the caller to specify the collection type they want as long as it implements ICollection perhaps with default to Collection</p> <p>I could make a set of classes one that uses ObservableCollection and one that does not say Foo and ObservableFoo.</p> <p>I could implement INotifyCollectionChanged in my class but that seems silly when ObservableCollection does it for me.</p> <p>Obviously I'm trying to keep the code clean and simple, but supporting data binding seems important.</p> <p>Any suggestions?</p> <p>Edit: Tried creating a Portable Class Library project using both alternatives.</p> <p>In class Foo I have</p> <pre><code> private readonly Collection&lt;string&gt; strings = new Collection&lt;string&gt;(); public ReadOnlyCollection&lt;string&gt; Strings { get { return new ReadOnlyCollection&lt;string&gt;(this.strings); } } </code></pre> <p>In class ObservableFoo I have</p> <pre><code> private readonly ObservableCollection&lt;string&gt; strings = new ObservableCollection&lt;string&gt;(); public ReadOnlyObservableCollection&lt;string&gt; Strings { get { return new ReadOnlyObservableCollection&lt;string&gt;(this.strings); } } </code></pre> <p>The very simple unit test code is</p> <pre><code> [TestMethod] public void TestMethod1() { var foo = new ObservableFoo(); // or new Foo() Assert.AreNotEqual(0, foo.Id); Assert.AreNotEqual(0, foo.Strings.Count); } </code></pre> <p>The only downside is that when I used ReadOnlyObservableCollection the test project got this compile error</p> <blockquote> <p>The type 'System.Collections.ObjectModel.ReadOnlyObservableCollection`1' is defined in an assembly that is not referenced. You must add a reference to assembly 'System.Windows, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e, Retargetable=Yes'</p> </blockquote> <p>So in this case, using ReadOnlyObservableCollection would force users to add a reference to System.Windows which is a downside.</p> <p><strong>Edit: I came up with a solution that I posted on my blog - see <a href="http://blogs.msdn.com/b/rjacobs/archive/2012/07/22/how-to-make-a-library-portable-and-data-binding-friendly-at-the-same-time.aspx" rel="nofollow">How to make a library portable and data binding friendly at the same time?</a></strong></p>
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    1. COI think it would be helpful if you provided a concise code sample.
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      1. USStrelok
 

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