Marshal.GetActiveObject() throws MK_E_UNAVAILABLE exception in C#

Question

The following vbscript code works prefectly fine:

Dim App 
Set App = GetObject("","QuickTest.Application")
App.Quit

But when I translate it into C# code as below:

class Program
{
    [STAThread]
    static void Main(string[] args)
    {
        object qtApp = Marshal.GetActiveObject("QuickTest.Application");
        (qtApp as QuickTest.Application).Quit();
    }
}

I get the exception:

An unhandled exception of type 'System.Runtime.InteropServices.COMException' occurred in mscorlib.dll

Additional information: (Exception from HRESULT: 0x800401E3 (MK_E_UNAVAILABLE))

I don't think the problem is related to ROT, because the vbscript code works. So what is wrong with the C# code?

Answer 1

Marshal.GetActiveObject use progID , check your progID, e.g. you could use this code for display objects in ROT

using System.Collections.Generic;
using System.Runtime.InteropServices;
using System.Runtime.InteropServices.ComTypes;
using System.Text;
using Microsoft.Win32;
...
class Program
{
    private const int S_OK = 0x00000000;

    [DllImport("ole32.dll")]
    private static extern int GetRunningObjectTable(uint reserved, out IRunningObjectTable pprot);

    [DllImport("ole32.dll")]
    private static extern int CreateBindCtx(uint reserved, out IBindCtx ppbc);      

    private static void OleCheck(string message, int result)
    {
        if (result != S_OK)
            throw new COMException(message, result);
    }

    private static System.Collections.Generic.IEnumerable<IMoniker> EnumRunningObjects()
    {           
        IRunningObjectTable objTbl;
        OleCheck("GetRunningObjectTable failed", GetRunningObjectTable(0, out objTbl));
        IEnumMoniker enumMoniker;
        IMoniker[] monikers = new IMoniker[1];
        objTbl.EnumRunning(out enumMoniker);
        enumMoniker.Reset();
        while (enumMoniker.Next(1, monikers, IntPtr.Zero) == S_OK)
        {
            yield return monikers[0];
        }
    }

    private static bool TryGetCLSIDFromDisplayName(string displayName, out string clsid)
    {
        var bBracket = displayName.IndexOf("{");
        var eBracket = displayName.IndexOf("}");
        if ((bBracket > 0) && (eBracket > 0) && (eBracket > bBracket))
        {
            clsid = displayName.Substring(bBracket, eBracket - bBracket + 1);
            return true;
        }
        else 
        {
            clsid = string.Empty;
            return false;
        }   
    }

    private static string ReadSubKeyValue(string keyName, RegistryKey key)
    {
        var subKey = key.OpenSubKey(keyName);
        if (subKey != null)
        {
            using(subKey)
            {
                var value = subKey.GetValue("");
                return value == null ? string.Empty : value.ToString();
            }
        }
        return string.Empty;
    }

    private static string GetMonikerString(IMoniker moniker)
    {
        IBindCtx ctx;
        OleCheck("CreateBindCtx failed", CreateBindCtx(0, out ctx));
        var sb = new StringBuilder();
        string displayName;
        moniker.GetDisplayName(ctx, null, out displayName);
        sb.Append(displayName);
        sb.Append('\t');
        string clsid; 
        if (TryGetCLSIDFromDisplayName(displayName, out clsid))
        {
            var regClass = Registry.ClassesRoot.OpenSubKey("\\CLSID\\" + clsid);
            if (regClass != null)
            {
                using(regClass)
                {
                    sb.Append(regClass.GetValue(""));
                    sb.Append('\t');
                    sb.Append(ReadSubKeyValue("ProgID", regClass));
                    sb.Append('\t');
                    sb.Append(ReadSubKeyValue("LocalServer32", regClass));
                }
            }
        }
        return sb.ToString();
    }

    [STAThread]
    public static void Main(string[] args)
    {
        Console.WriteLine("DisplayName\tRegId\tProgId\tServer");
        foreach(var moniker in EnumRunningObjects())
        {
            Console.WriteLine(GetMonikerString(moniker));
        }
    }
}