CreateInstanceAndUnwrap locks up dll under IIEXpress

Question

I have an ASP.NET site that does CreateInstanceAndUnwrap:

var setup = new AppDomainSetup
        {
            ShadowCopyFiles = "true",
            ShadowCopyDirectories = "true",
            ApplicationBase = textPipe["host"] == "web" ? Path.GetDirectoryName(new Uri(Assembly.GetExecutingAssembly().CodeBase).LocalPath) : Environment.CurrentDirectory,
            ConfigurationFile = $"UnitTests/{testProject}/app.config"
        };

        var domain = AppDomain.CreateDomain("UnitTestDomain", null, setup);

        var type = typeof(TestProxy);
        var instance = (TestProxy)domain.CreateInstanceAndUnwrap(
            type.Assembly.FullName,
            type.FullName);

All works, but after I run this code under IISExpress on my dev workstation, I can no longer recompile the DLLs -- the error I get is "Unable to copy file .... because it is being used by another process." I have to stop IISExpress before recompiling. This will be definitely be a bigger issue in production, if it will be necessary to stop AppPool prior to each deployment.

Not sure why the files are locked? I am using the ShadowCopyFiles and ShadowCopyDirectories, but that doesn't seem to help.

What can I do to avoid locking files? Thank you.

Answer 1

It's been a while since I've had to deal with AppDomain, but I think maybe calling

AppDomain.Unload(domain)

at the end of the relevant request should free the assembly. If there is a need for it to be in memory continually (if it is too expensive to reload per request), then unloading the domain probably won't work for you.