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POLINQ: How to get items from an inner list into one list?
 

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  1. POLINQ: How to get items from an inner list into one list?
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    <p>Having the following classes (highly simplified):</p> <pre><code>public class Child { public string Label; public int CategoryNumber; public int StorageId; } public class Parent { public string Label; public List&lt;Child&gt; Children = new List&lt;Child&gt;(); } </code></pre> <p>And having the following data:</p> <pre><code>var parents = new List&lt;Parent&gt;(); var parent = new Parent() {Label="P1"}; parent.Children.Add(new Child() {Label="C1", CategoryNumber=1, StorageId=10}); parent.Children.Add(new Child() {Label="C2", CategoryNumber=2, StorageId=20}); parents.Add(parent); parent = new Parent() {Label="P2"}; parent.Children.Add(new Child() {Label="C3", CategoryNumber=1, StorageId=10}); parent.Children.Add(new Child() {Label="C4", CategoryNumber=2, StorageId=30}); parents.Add(parent); parent = new Parent() {Label="P3"}; parent.Children.Add(new Child() {Label="C5", CategoryNumber=3, StorageId=10}); parent.Children.Add(new Child() {Label="C6", CategoryNumber=2, StorageId=40}); parents.Add(parent); </code></pre> <p>Now, how would I get a list of children (with CategoryNumber=2) from the list of parents containing at least one child with CategoryNumber = 1 ?</p> <p>I can do the following but it does not appear to be optimal:</p> <pre><code>var validParents = from p in parents where p.Children.Any (c =&gt; c.CategoryNumber==1) select p; var selectedChildren = validParents.Select(p =&gt; from c in p.Children where c.CategoryNumber == 2 select c); </code></pre> <p>Here's what I get for selectedChildren:</p> <ul> <li><code>IEnumerable&lt;IEnumerable&lt;Child&gt;&gt;</code> <ul> <li><code>IEnumerable&lt;Child&gt;</code> <ul> <li>C2 2 20</li> </ul></li> <li><code>IEnumerable&lt;Child&gt;</code> <ul> <li>C4 2 30</li> </ul></li> </ul></li> </ul> <p>Is it possible to only have one flat list containing the two children elements instead of two sub-list? How would it translate in LINQ ?</p>
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