title: ASP.NET UpdatePanel library reference errors
body: <p>I am having a problem with VS 2010 apparently losing it's ability to load an UpdatePanel in the middle of development and it is driving me crazy.  I am using VS2010 and building a user control with .NET 3.5, targeting DNN 5.x.</p>
  
  <p>I have created a control to be used on a DNN website that utilizes an update panel.  When I develop the control by FTPing to the website and developing on it, everything works just fine.  I decided to move development to a local copy of DNN and create a web application project for the control.  Everything was working just fine at first.  After a few builds, I started to receive the following errors:</p>
  
  <blockquote>
    <p>The type or namespace name
    'UpdateProgress' does not exist in the
    namespace
    'System.Web.UI.WebControls.WebParts'
    (are you missing an assembly
    reference?)</p>
    
    <p>The type or namespace name
    'UpdatePanel' does not exist in the
    namespace
    'System.Web.UI.WebControls.WebParts'
    (are you missing an assembly
    reference?)</p>
  </blockquote>
  
  <p>I figured I had messed something up along the way and screwed up a reference to the libraries, so I unloaded everything and reloaded the library references.  I continued to get the error and could not compile the control.  Finally, I decided to redo the entire project and import the code I had already written.  Everything was working just fine until a few builds later when the same error popped up.</p>
  
  <p>I followed all of the same steps, unloading the references, reloading them, and finally deleting the project.  Each time I create a new project, and copy the exact same code into the .ascx files, they work just fine...for a few builds.  Last night, I compiled the library and tested the changes.  Everything was great so I closed the project and turned off the machine.  Turned it on this morning and received the build errors.  It is like I have a ticking timebomb in my computer that just shuts these things off.</p>
  
  <p>Any ideas on what I am missing that might be causing this?  I don't know why a library would flicker on and off like this.  I have yet to run into this sort of a problem with any other project on my local machine and I really don't want to develop this through FTPing to the website, again.  Bleh!</p>