Enumerate all AppDomains without mscoree

Question

How to enumerate all the process' domains without referencing mscoree. Is it possible? I found some solution from 2007 year somewhere in the Internet. But it enumerates and empty collection.

Here's the code:

public static class DomainHelper
{
    public static AppDomain[] LoadedDomains
    {
        get
        {
            var loadedDomains = new List<AppDomain>();
            var runtimeHost = new CorRuntimeHost() as ICorRuntimeHost;

            try
            {
                var enumeration = IntPtr.Zero;
                runtimeHost.EnumDomains(out enumeration);

                try
                {
                    object nextDomain = null;
                    runtimeHost.NextDomain(enumeration, ref nextDomain);

                    while (nextDomain != null)
                    {
                        loadedDomains.Add((AppDomain) nextDomain);
                        nextDomain = null;
                        runtimeHost.NextDomain(enumeration, ref nextDomain);
                    }
                }
                finally
                {
                    runtimeHost.CloseEnum(enumeration);
                }
            }
            finally
            {
                Marshal.ReleaseComObject(runtimeHost);
            }

            return loadedDomains.ToArray();
        }
    }

    [ComImport]
    [Guid("CB2F6723-AB3A-11d2-9C40-00C04FA30A3E")]
    private class CorRuntimeHost // : ICorRuntimeHost
    {}

    [Guid("CB2F6722-AB3A-11D2-9C40-00C04FA30A3E")]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    private interface ICorRuntimeHost
    {
        void CloseEnum(IntPtr enumHandle);
        void CreateDomain();
        void CreateDomainEx();
        void CreateDomainSetup();
        void CreateEvidence();
        void CreateLogicalThreadState();
        void CurrentDomain();
        void DeleteLogicalThreadState();
        void EnumDomains(out IntPtr enumHandle);
        void GetConfiguration();
        void GetDefaultDomain();
        void LocksHeldByLogicalThread();
        void MapFile();
        void NextDomain(IntPtr enumHandle, [MarshalAs(UnmanagedType.IUnknown)] ref object appDomain);
        void Start();
        void Stop();
        void SwitchInLogicalThreadState();
        void SwitchOutLogicalThreadState();
        void UnloadDomain();
    }
}

Answer 1

Not referencing mscoree.tlb is what is getting you into trouble, the ICorRuntimeHost is declared wrong. The method order is completely mixed up, unclear how that happened. Life was also much simpler back in 2007, the hosting interface was drastically redesigned for .NET 4.0 and ICorRuntimeHost is deprecated. It still works though, surely for a while to come.

I'll post code that runs on .NET 4.0 and higher. Proper approach is to start with ICLRMetaHost. Then obtain the ICLRRuntimeInfo instance for the runtime instance that you are interested in. Keep in mind that .NET 4.0 supports in-process side-by-side instancing of the CLR, you'll want to find the one that your code is using. The ICLRRuntimeInfo::GetInterface() method can then return an instance to the legacy ICorRuntimeHost interface.

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;

public static class CLRUtil {
    public static IEnumerable<_AppDomain> EnumAppDomains() {
        // Obtain ICLRMetaHost interface
        object objHost;
        int hr = CLRCreateInstance(ref CLSID_CLRMetaHost, ref IID_CLRMetaHost, out objHost);
        if (hr < 0) throw new COMException("Cannot create meta host", hr);
        var host = (ICLRMetaHost)objHost;

        // Obtain ICLRRuntimeInfo interface
        var vers = Environment.Version;
        var versString = string.Format("v{0}.{1}.{2}", vers.Major, vers.Minor, vers.Build);
        var objRuntime = host.GetRuntime(versString, ref IID_CLRRuntimeInfo);
        var runtime = (ICLRRuntimeInfo)objRuntime;
        bool started;
        uint flags;
        runtime.IsStarted(out started, out flags);
        if (!started) throw new COMException("CLR not started??");

        // Obtain legacy ICorRuntimeHost interface and iterate appdomains
        var V2Host = (ICorRuntimeHost)runtime.GetInterface(ref CLSID_CorRuntimeHost, ref IID_CorRuntimeHost);
        IntPtr hDomainEnum;
        V2Host.EnumDomains(out hDomainEnum);
        for (;;) {
            _AppDomain domain = null;
            V2Host.NextDomain(hDomainEnum, out domain);
            if (domain == null) break;
            yield return domain;
        }
        V2Host.CloseEnum(hDomainEnum);
    }

    private static Guid CLSID_CLRMetaHost = new Guid(0x9280188d, 0xe8e, 0x4867, 0xb3, 0xc, 0x7f, 0xa8, 0x38, 0x84, 0xe8, 0xde);
    private static Guid IID_CLRMetaHost = new Guid(0xD332DB9E, 0xB9B3, 0x4125, 0x82, 0x07, 0xA1, 0x48, 0x84, 0xF5, 0x32, 0x16);
    private static Guid IID_CLRRuntimeInfo = new Guid(0xBD39D1D2, 0xBA2F, 0x486a, 0x89, 0xB0, 0xB4, 0xB0, 0xCB, 0x46, 0x68, 0x91);
    private static Guid CLSID_CorRuntimeHost = new Guid(0xcb2f6723, 0xab3a, 0x11d2, 0x9c, 0x40, 0x00, 0xc0, 0x4f, 0xa3, 0x0a, 0x3e);
    private static Guid IID_CorRuntimeHost = new Guid(0xcb2f6722, 0xab3a, 0x11d2, 0x9c, 0x40, 0x00, 0xc0, 0x4f, 0xa3, 0x0a, 0x3e);

    [DllImport("mscoree.dll")]
    private static extern int CLRCreateInstance(ref Guid clsid, ref Guid iid,
        [MarshalAs(UnmanagedType.Interface)] out object ptr);

    [ComImport, Guid("D332DB9E-B9B3-4125-8207-A14884F53216"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    private interface ICLRMetaHost {
        [return: MarshalAs(UnmanagedType.Interface)]
        object GetRuntime(string version, ref Guid iid);
        // Rest omitted
    }

    [ComImport, Guid("BD39D1D2-BA2F-486a-89B0-B4B0CB466891"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    private interface ICLRRuntimeInfo {
        void GetVersionString(char[] buffer, int bufferLength);
        void GetRuntimeDirectory(char[] buffer, int bufferLength);
        bool IsLoaded(IntPtr hProcess);
        void LoadErrorString(uint id, char[] buffer, int bufferLength, int lcid);
        void LoadLibrary(string path, out IntPtr hMdodule);
        void GetProcAddress(string name, out IntPtr addr);
        [return: MarshalAs(UnmanagedType.Interface)]
        object GetInterface(ref Guid clsid, ref Guid iid);
        bool IsLoadable();
        void SetDefaultStartupFlags(uint flags, string configFile);
        void GetDefaultStartupFlags(out uint flags, char[] configFile, int configFileLength);
        void BindAsLegacyV2Runtime();
        void IsStarted(out bool started, out uint flags);
    }

    [ComImport, Guid("CB2F6722-AB3A-11d2-9C40-00C04FA30A3E"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    private interface ICorRuntimeHost {
        void CreateLogicalThreadState();
        void DeleteLogicalThreadState();
        void SwitchinLogicalThreadState(IntPtr cookie);
        void SwitchoutLogicalThreadState(out IntPtr cookie);
        void LocksHeldByLogicalThread(out int count);
        void MapFile(IntPtr hFile, out IntPtr address);
        void GetConfiguration(out IntPtr config);
        void Start();
        void Stop();
        void CreateDomain(string name, object identity, out _AppDomain domain);
        void GetDefaultDomain(out _AppDomain domain);
        void EnumDomains(out IntPtr hEnum);
        void NextDomain(IntPtr hEnum, out _AppDomain domain);
        void CloseEnum(IntPtr hEnum);
        // rest omitted
    }
}

Sample usage:

class Program {
    static void Main(string[] args) {
        AppDomain.CreateDomain("Example");
        foreach (var domain in CLRUtil.EnumAppDomains()) {
            Console.WriteLine("Found appdomain {0}", domain.FriendlyName);
        }
        Console.ReadLine();
    }
}

Output:

Found appdomain ConsoleApplication1.vshost.exe
Found appdomain Example