Using ApplicationHost.CreateApplicationHost() to create an Asp.Net post, while loading assemblies from another location

Question

I'm trying to use CreateApplicationHost to create an Asp.Net application host for a simple web server, however I'm getting a System.IO.FileNotFoundException when it attempts to create an instance of my marshalling object:

host = (MyMarshaller)ApplicationHost.CreateApplicationHost((MyMarshaller), virtualDir, physicalDir);

I believe that this error is because it cannot find the assembly containing the class MyMarshaller - if I put this assembly in the bin directory of physicalDir then everything works fine, however I don't want to do this (I also don't want to place my assembly in the GAC either).

Is there any way that I can control where CreateApplicationHost looks for my assembly? (Note that MyMarshaller class is conted in the same assembly as the above line of code)

Answer 1

The short answer is that it isn't possible to do this, however the Cassini source revealed an alternative solution.

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Update

The above link no longer works, however the CassiniDev project on CodePlex appears to be pretty close (possibly a derivative work) and contains the same solution.

The solution is to avoid using CreateApplicationHost and "do it yourself" instead - in this case use reflection to create an instance of the internal "BuildManagerHost" type and call "RegisterAssembly", like so

/// <remarks>
/// This is Dmitry's hack to enable running outside of GAC.
/// There are some errors being thrown when running in proc
/// </remarks>
private object CreateWorkerAppDomainWithHost(string virtualPath, string physicalPath, Type hostType,int port)
{
    // create BuildManagerHost in the worker app domain
    //ApplicationManager appManager = ApplicationManager.GetApplicationManager();
    Type buildManagerHostType = typeof(HttpRuntime).Assembly.GetType("System.Web.Compilation.BuildManagerHost");
    IRegisteredObject buildManagerHost = ApplicationManager.CreateObject(_appId, buildManagerHostType, virtualPath,
                                                                  physicalPath, false);
    
    // call BuildManagerHost.RegisterAssembly to make Host type loadable in the worker app domain
    buildManagerHostType.InvokeMember("RegisterAssembly",
                                      BindingFlags.Instance | BindingFlags.InvokeMethod | BindingFlags.NonPublic,
                                      null,
                                      buildManagerHost,
                                      new object[] { hostType.Assembly.FullName, hostType.Assembly.Location });
    
    // create Host in the worker app domain
    // FIXME: getting FileLoadException Could not load file or assembly 'WebDev.WebServer20, Version=4.0.1.6, Culture=neutral, PublicKeyToken=f7f6e0b4240c7c27' or one of its dependencies. Failed to grant permission to execute. (Exception from HRESULT: 0x80131418)
    // when running dnoa 3.4 samples - webdev is registering trust somewhere that we are not
    return ApplicationManager.CreateObject(_appId, hostType, virtualPath, physicalPath, false);
}