title: What are your favorite extension methods for C#? (codeplex.com/extensionoverflow)
body: <p>Let's make a list of answers where you post your excellent and favorite <a href="http://en.wikipedia.org/wiki/Extension_method" rel="nofollow noreferrer">extension methods</a>. </p>
  
  <p>The requirement is that the full code must be posted and a example and an explanation on how to use it.</p>
  
  <p>Based on the high interest in this topic I have setup an Open Source Project called extensionoverflow on <a href="http://www.codeplex.com/extensionoverflow" rel="nofollow noreferrer"><strong>Codeplex</strong></a>. </p>
  
  <p><strong>Please mark your answers with an acceptance to put the code in the Codeplex project.</strong></p>
  
  <p><strong>Please post the full sourcecode and not a link.</strong></p>
  
  <p><strong>Codeplex News:</strong></p>
  
  <p>24.08.2010 The Codeplex page is now here:  <a href="http://extensionoverflow.codeplex.com/" rel="nofollow noreferrer">http://extensionoverflow.codeplex.com/</a></p>
  
  <p>11.11.2008 <strong>XmlSerialize / XmlDeserialize</strong> is now <a href="http://www.codeplex.com/extensionoverflow/SourceControl/FileView.aspx?itemId=284374&amp;changeSetId=17001" rel="nofollow noreferrer">Implemented</a> and <a href="http://www.codeplex.com/extensionoverflow/SourceControl/FileView.aspx?itemId=288847&amp;changeSetId=17001" rel="nofollow noreferrer">Unit Tested</a>.</p>
  
  <p>11.11.2008 There is still room for more developers. ;-) <strong>Join NOW!</strong></p>
  
  <p>11.11.2008 Third contributer joined <a href="http://www.codeplex.com/extensionoverflow" rel="nofollow noreferrer">ExtensionOverflow</a>, welcome to <a href="http://www.codeplex.com/site/users/view/BKristensen" rel="nofollow noreferrer">BKristensen</a></p>
  
  <p>11.11.2008 <strong>FormatWith</strong> is now <a href="http://www.codeplex.com/extensionoverflow/SourceControl/FileView.aspx?itemId=284374&amp;changeSetId=16839" rel="nofollow noreferrer">Implemented</a> and <a href="http://www.codeplex.com/extensionoverflow/SourceControl/FileView.aspx?itemId=288847&amp;changeSetId=16839" rel="nofollow noreferrer">Unit Tested</a>.</p>
  
  <p>09.11.2008 Second contributer joined <a href="http://www.codeplex.com/extensionoverflow" rel="nofollow noreferrer">ExtensionOverflow</a>. welcome to <a href="https://stackoverflow.com/users/3055/chakrit">chakrit</a>.</p>
  
  <p>09.11.2008 We need more developers. ;-)</p>
  
  <p>09.11.2008 <strong>ThrowIfArgumentIsNull</strong> in now <a href="http://www.codeplex.com/extensionoverflow/SourceControl/FileView.aspx?itemId=278942&amp;changeSetId=16468" rel="nofollow noreferrer">Implemented</a> and <a href="http://www.codeplex.com/extensionoverflow/SourceControl/FileView.aspx?itemId=284112&amp;changeSetId=16468" rel="nofollow noreferrer">Unit Tested</a> on Codeplex.</p>