title: MVC6 Can't find app.UseStaticFiles() in Startup
body: <p>I am playing around the new ASPNET 5 beta using the latest version of Visual Studio Code (v0.3). I don't want to put the VS2015 RC on my work machine. I have a barebones (Hello World) MVC6 app which I've gotten running after figuring out the basics of the dn* command line tools.</p>
  
  <p>Now I want to serve a static file. I've added Microsoft.AspNet.StaticFiles to my project.json file and restored the packages.</p>
  
  <p>My project.json:</p>
  
  <pre><code>{
      "version": "1.0.0-*",
      "webroot": "wwwroot",
      "exclude": [
          "wwwroot"
      ],
      "packExclude": [
          "**.kproj",
          "**.user",
          "**.vspscc"
      ],
      "dependencies": {
          "Kestrel": "1.0.0-*",
          "Microsoft.AspNet.Diagnostics": "1.0.0-*",
          "Microsoft.AspNet.Mvc": "6.0.0-*",
          "Microsoft.AspNet.Server.IIS": "1.0.0-*",
          "Microsoft.AspNet.Server.WebListener": "1.0.0-*",
          "Microsoft.AspNet.StaticFiles": "1.0.0-*"
      },
      "commands": {
          "web": "Microsoft.AspNet.Hosting --server Microsoft.AspNet.Server.WebListener --server.urls http://localhost:8080",
          "kestrel": "Microsoft.AspNet.Hosting --server Kestrel --server.urls http://localhost:8080"
      },
      "frameworks": {
           "dnx451": { },
           "dnxcore50": { }
      }
  }
  </code></pre>
  
  <p>My Startup.cs:</p>
  
  <pre><code>using Microsoft.AspNet.Builder;
  using Microsoft.Framework.DependencyInjection;
  
  namespace EmailViewer
  {
      public class Startup
      {
          public void ConfigureServices(IServiceCollection services)
          {
              services.AddMvc();
          }
  
          public void Configure(IApplicationBuilder app)
          {            
              app.UseErrorPage();
              app.UseStaticFiles(); 
              app.UseMvcWithDefaultRoute();
              app.UseWelcomePage(); 
          }
      }
  }
  </code></pre>
  
  <p>Everything works fine until I include app.UseStaticFiles() at which point I get the following error:</p>
  
  <pre><code>System.IO.FileLoadException: Could not load file or assembly 'EmailViewer' or one of its dependencies. General Exception (Exception from HRESULT: 0x80131500)
  File name: 'EmailViewer' ---&gt; Microsoft.Framework.Runtime.Roslyn.RoslynCompilationException: C:\src\fx5\EmailViewer\Startup.cs(16,13): error CS7069: Reference to type 'IApplicationBuilder' claims it is defined in 'Microsoft.AspNet.Http', but it could not be found
     at Microsoft.Framework.Runtime.Roslyn.RoslynProjectReference.Load(IAssemblyLoadContext loadContext)
     at Microsoft.Framework.Runtime.Loader.ProjectAssemblyLoader.Load(AssemblyName assemblyName, IAssemblyLoadContext loadContext)
     at Microsoft.Framework.Runtime.Loader.ProjectAssemblyLoader.Load(AssemblyName assemblyName)
     at dnx.host.LoaderContainer.Load(AssemblyName assemblyName)
     at dnx.host.DefaultLoadContext.LoadAssembly(AssemblyName assemblyName)
     at Microsoft.Framework.Runtime.Loader.AssemblyLoaderCache.GetOrAdd(AssemblyName name, Func`2 factory)
     at Microsoft.Framework.Runtime.Loader.LoadContext.LoadAssemblyImpl(AssemblyName assemblyName)
     at Microsoft.Framework.Runtime.Loader.LoadContext.TryLoadAssembly(LoadContext context, AssemblyName assemblyName, Assembly&amp; assembly)
     at Microsoft.Framework.Runtime.Loader.LoadContext.ResolveAssembly(Object sender, ResolveEventArgs args)
     at System.AppDomain.OnAssemblyResolveEvent(RuntimeAssembly assembly, String assemblyFullName)
     at System.Reflection.RuntimeAssembly._nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark&amp; stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
     at System.Reflection.RuntimeAssembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, RuntimeAssembly locationHint, StackCrawlMark&amp; stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
     at System.Reflection.RuntimeAssembly.InternalLoadAssemblyName(AssemblyName assemblyRef, Evidence assemblySecurity, RuntimeAssembly reqAssembly, StackCrawlMark&amp; stackMark, IntPtr pPrivHostBinder, Boolean throwOnFileNotFound, Boolean forIntrospection, Boolean suppressSecurityChecks)
     at System.Reflection.Assembly.Load(AssemblyName assemblyRef)
     at Microsoft.AspNet.Hosting.Startup.StartupLoader.FindStartupType(String startupAssemblyName, IList`1 diagnosticMessages)
     at Microsoft.AspNet.Hosting.Internal.HostingEngine.EnsureStartup()
     at Microsoft.AspNet.Hosting.Internal.HostingEngine.EnsureApplicationServices()
     at Microsoft.AspNet.Hosting.Internal.HostingEngine.Start()
     at Microsoft.AspNet.Hosting.Program.Main(String[] args)
  --- End of stack trace from previous location where exception was thrown ---
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
     at Microsoft.Framework.Runtime.Common.EntryPointExecutor.Execute(Assembly assembly, String[] args, IServiceProvider serviceProvider)
     at Microsoft.Framework.ApplicationHost.Program.ExecuteMain(DefaultHost host, String applicationName, String[] args)
     at Microsoft.Framework.ApplicationHost.Program.Main(String[] args)
  --- End of stack trace from previous location where exception was thrown ---
     at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
     at Microsoft.Framework.Runtime.Common.EntryPointExecutor.Execute(Assembly assembly, String[] args, IServiceProvider serviceProvider)
     at dnx.host.Bootstrapper.RunAsync(List`1 args, IRuntimeEnvironment env)
     at dnx.host.RuntimeBootstrapper.ExecuteAsync(String[] args)
     at dnx.host.RuntimeBootstrapper.Execute(String[] args)
  
  
  Microsoft.Framework.Runtime.Roslyn.RoslynCompilationException: C:\src\fx5\EmailViewer\Startup.cs(16,13): error CS7069: Reference to type 'IApplicationBuilder' claims it is defined in 'Microsoft.AspNet.Http', but it could not be found
     at Microsoft.Framework.Runtime.Roslyn.RoslynProjectReference.Load(IAssemblyLoadContext loadContext)
     at Microsoft.Framework.Runtime.Loader.ProjectAssemblyLoader.Load(AssemblyName assemblyName, IAssemblyLoadContext loadContext)
     at Microsoft.Framework.Runtime.Loader.ProjectAssemblyLoader.Load(AssemblyName assemblyName)
     at dnx.host.LoaderContainer.Load(AssemblyName assemblyName)
     at dnx.host.DefaultLoadContext.LoadAssembly(AssemblyName assemblyName)
     at Microsoft.Framework.Runtime.Loader.AssemblyLoaderCache.GetOrAdd(AssemblyName name, Func`2 factory)
     at Microsoft.Framework.Runtime.Loader.LoadContext.LoadAssemblyImpl(AssemblyName assemblyName)
     at Microsoft.Framework.Runtime.Loader.LoadContext.TryLoadAssembly(LoadContext context, AssemblyName assemblyName, Assembly&amp; assembly)
     at Microsoft.Framework.Runtime.Loader.LoadContext.ResolveAssembly(Object sender, ResolveEventArgs args)
     at System.AppDomain.OnAssemblyResolveEvent(RuntimeAssembly assembly, String assemblyFullName)
  </code></pre>
  
  <p>I've tried using these versions:</p>
  
  <ul>
  <li>1.0.0-beta4</li>
  <li>1.0.0-beta6-12114</li>
  </ul>
  
  <p>I can't figure out what I'm doing wrong. Any ideas? Thanks in advance!</p>