enumerating assemblies in GAC

Question

How can I enumerate all available assemblies in GAC in C#?

Actually I am facing an issue with a stupid code - the assembly called Telerik.Web.UI.dll is referred and

Answer 1

Check the way how fusion.dll is used in ILSpy to enumerate all the GAC assemblies.

Fusion COM Wrappers

using System;
using System.Runtime.InteropServices;
using System.Text;

namespace GacWithFusion
{
    // .NET Fusion COM interfaces
    [ComImport, Guid("CD193BC0-B4BC-11D2-9833-00C04FC31D2E"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IAssemblyName
    {
        [PreserveSig]
        int SetProperty(uint PropertyId, IntPtr pvProperty, uint cbProperty);

        [PreserveSig]
        int GetProperty(uint PropertyId, IntPtr pvProperty, ref uint pcbProperty);

        [PreserveSig]
        int Finalize();

        [PreserveSig]
        int GetDisplayName([Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder szDisplayName,
                           ref uint pccDisplayName,
                           uint dwDisplayFlags);

        [PreserveSig]
        int BindToObject(object refIID,
                         object pAsmBindSink,
                         IApplicationContext pApplicationContext,
                         [MarshalAs(UnmanagedType.LPWStr)] string szCodeBase,
                         long llFlags,
                         int pvReserved,
                         uint cbReserved,
                         out int ppv);

        [PreserveSig]
        int GetName(ref uint lpcwBuffer,
                    [Out(), MarshalAs(UnmanagedType.LPWStr)] StringBuilder pwzName);

        [PreserveSig]
        int GetVersion(out uint pdwVersionHi, out uint pdwVersionLow);

        [PreserveSig]
        int IsEqual(IAssemblyName pName,
                    uint dwCmpFlags);

        [PreserveSig]
        int Clone(out IAssemblyName pName);
    }

    [ComImport(), Guid("7C23FF90-33AF-11D3-95DA-00A024A85B51"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IApplicationContext
    {
        void SetContextNameObject(IAssemblyName pName);

        void GetContextNameObject(out IAssemblyName ppName);

        void Set([MarshalAs(UnmanagedType.LPWStr)] string szName,
                 int pvValue,
                 uint cbValue,
                 uint dwFlags);

        void Get([MarshalAs(UnmanagedType.LPWStr)] string szName,
                 out int pvValue,
                 ref uint pcbValue,
                 uint dwFlags);

        void GetDynamicDirectory(out int wzDynamicDir,
                                 ref uint pdwSize);
    }

    [ComImport(), Guid("21B8916C-F28E-11D2-A473-00C04F8EF448"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    internal interface IAssemblyEnum
    {
        [PreserveSig]
        int GetNextAssembly(out IApplicationContext ppAppCtx,
                            out IAssemblyName ppName,
                            uint dwFlags);

        [PreserveSig]
        int Reset();

        [PreserveSig]
        int Clone(out IAssemblyEnum ppEnum);
    }

    internal static class Fusion
    {
        // dwFlags: 1 = Enumerate native image (NGEN) assemblies
        //          2 = Enumerate GAC assemblies
        //          4 = Enumerate Downloaded assemblies
        //
        [DllImport("fusion.dll", CharSet = CharSet.Auto)]
        internal static extern int CreateAssemblyEnum(out IAssemblyEnum ppEnum,
                                                      IApplicationContext pAppCtx,
                                                      IAssemblyName pName,
                                                      uint dwFlags,
                                                      int pvReserved);
    }
}

Main

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Text;

namespace GacWithFusion
{
    public class Program
    {
        static void Main(string[] args)
        {
            foreach (var assemblyName in GetGacAssemblyFullNames())
            {
                Console.WriteLine(assemblyName.FullName);
            }
        }

        public static IEnumerable GetGacAssemblyFullNames()
        {
            IApplicationContext applicationContext;
            IAssemblyEnum assemblyEnum;
            IAssemblyName assemblyName;

            Fusion.CreateAssemblyEnum(out assemblyEnum, null, null, 2, 0);
            while (assemblyEnum.GetNextAssembly(out applicationContext, out assemblyName, 0) == 0)
            {
                uint nChars = 0;
                assemblyName.GetDisplayName(null, ref nChars, 0);

                StringBuilder name = new StringBuilder((int)nChars);
                assemblyName.GetDisplayName(name, ref nChars, 0);

                AssemblyName a = null;
                try
                {
                    a = new AssemblyName(name.ToString());
                }
                catch (Exception)
                {
                }

                if (a != null)
                {
                    yield return a;
                }
            }
        }
    }
}