title: What is System.Web.Extensions for?
body: <p>By default ASP.NET 3.5 Web App project has references to assemblies <code>System.Data.DataSetExtensions.dll</code> and <code>System.Web.Extensions.dll</code>.</p>
  
  <p>With <code>System.Data.DataSetExtensions</code> everything is clear for me, it contains such useful extension methods as <code>DataTable.AsEnumerable()</code> and <code>DataTable.CopyToDataTable()</code>.</p>
  
  <p>And what about <code>System.Web.Extensions.dll</code>? What useful members could you mention to use?</p>