title: Select object from nested collection using Linq
body: <p>I have a class structure something like this:</p>
  
  <pre><code>class MyClass
  {
      public IEnumerable&lt;AttributeGroup&gt; AttributeGroups { get; set; }
  }
  
  class AttributeGroup
  {
      public IEnumerable&lt;Attribute&gt; Attributes { get; set; }
  }
  
  class Attribute
  {
      public string SomeProp { get; set; }
  }
  </code></pre>
  
  <p>I need to get all 'Attributes' which has a specific 'SomeProp' value no matter which Attribute Group they belong to.</p>
  
  <p>For example, <code>SomeProperty== 'A'</code> can be found in both <code>MyClassObj.AttributeGroup[0]</code> and <code>MyClassObj.AttributeGroup[5]</code> and I need to write a Linq (or something like that) to fetch two objects from these two different attributegroups.</p>
  
  <p>Any suggestion?</p>