title: The designer could not be shown for this file because none of the classes within it can be designed
body: <p>We have the following shared component:</p>
  
  <pre><code>public class OurServiceBase : System.ServiceProcess.ServiceBase
  </code></pre>
  
  <p>This class has functionality we want in all our downstream services, such as standardized execution scheduling and logging functionality.</p>
  
  <p>In a new project, I add the following:</p>
  
  <pre><code>public class MyService : System.ServiceProcess.ServiceBase
  </code></pre>
  
  <p>In the Windows Designer, the class shows properly.</p>
  
  <p>When I change the service to derive from OurServiceBase</p>
  
  <pre><code>public class MyService : OurSharedLibrary.OurServiceBase
  </code></pre>
  
  <p>The designer stops working:</p>
  
  <p><img src="https://i.stack.imgur.com/SUw9m.jpg" alt="Error screenshot"></p>
  
  <p>The full error is:
  The designer could not be shown for this file because none of the classes within it can be designed. The designer inspected the following classes in the file: EmailProcessor --- The base class 'OurSharedLibrary.CienaServiceBase' could not be loaded. Ensure the assembly has been referenced and that all projects have been built. </p>
  
  <p>The proper assemblies are referenced, the project builds.  I don't understand why the designer is flipping out over this since my service ultimately does derive from a designable class.</p>
  
  <p>Any suggestions would be most welcome.</p>
  
  <p>Bit more information - the call stack from the designer when it renders the error about not being able to design the derived service:</p>
  
  <pre><code>at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.EnsureDocument(IDesignerSerializationManager manager)
  at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager manager)
  at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager serializationManager)
  at System.ComponentModel.Design.Serialization.BasicDesignerLoader.BeginLoad(IDesignerLoaderHost host) 
  </code></pre>
  
  <p>7/19/2011 2:34PM EDT New discovery.  </p>
  
  <p>Class "OurServiceBase" exists in a separate project (usually referenced as a DLL only).  On a whim, I copied the base class file into my project, built, and opened the designer.  It worked!  When I removed the base class file again and returned to the external DLL reference, the designer broke again.</p>