AssemblyName.CodeBase stripped from AssemblyName before going to Resolving event handler

[AArnott]

On .NET Framework, Assembly.Load(AssemblyName) will consider the value of AssemblyName.CodeBase before failing to load the assembly.
On .NET Core, not only is the CodeBase property ignored, but it's omitted from a copy of the AssemblyName that is given to the AssemblyLoadContext.Resolving event handler, where I had hoped to re-implement the .NET Framework behavior of honoring that property.

For backwards compatibility when an app migrates from NetFX to .NET Core, being able to see the CodeBase property would be useful. Why is it omitted? Would you consider modifying .NET Core to propagate that property when calling the Resolving event handler to give the host more options for finding assemblies?

Repro:

using System;
using System.Reflection;
#if NETCOREAPP
using System.Runtime.Loader;
#endif

namespace ConsoleApp1
{
    internal class Program
    {
        static void Main(string[] args)
        {
#if NETCOREAPP
            AssemblyLoadContext.Default.Resolving += ALC_Resolving;
#endif

            AssemblyName an = AssemblyName.GetAssemblyName(@"C:\git\threading\bin\SosThreadingTools\Debug\net472\SosThreadingTools.dll");
#if NETCOREAPP
           // not necessary on net472
           an.CodeBase = @"C:\git\threading\bin\SosThreadingTools\Debug\net472\SosThreadingTools.dll";
#endif

            Assembly a = Assembly.Load(an); // throws on net5.0
            Console.WriteLine("a is not null: " + (a is object));
        }

#if NETCOREAPP
        private static Assembly ALC_Resolving(AssemblyLoadContext arg1, AssemblyName arg2)
        {
            if (!string.IsNullOrEmpty(arg2.CodeBase)) // null on net5.0
            {
                return arg1.LoadFromAssemblyPath(arg2.CodeBase);
            }

            return null;
        }
#endif
    }
}

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Issue Details

---

On .NET Framework, Assembly.Load(AssemblyName) will consider the value of AssemblyName.CodeBase before failing to load the assembly.
On .NET Core, not only is the CodeBase property ignored, but it's omitted from a copy of the AssemblyName that is given to the AssemblyLoadContext.Resolving event handler, where I had hoped to re-implement the .NET Framework behavior of honoring that property.

For backwards compatibility when an app migrates from NetFX to .NET Core, being able to see the CodeBase property would be useful. Why is it omitted? Would you consider modifying .NET Core to propagate that property when calling the Resolving event handler to give the host more options for finding assemblies?

Repro:

using System;
using System.Reflection;
#if NETCOREAPP
using System.Runtime.Loader;
#endif

namespace ConsoleApp1
{
    internal class Program
    {
        static void Main(string[] args)
        {
#if NETCOREAPP
            AssemblyLoadContext.Default.Resolving += ALC_Resolving;
#endif

            AssemblyName an = AssemblyName.GetAssemblyName(@"C:\git\threading\bin\SosThreadingTools\Debug\net472\SosThreadingTools.dll");
            an.CodeBase = @"C:\git\threading\bin\SosThreadingTools\Debug\net472\SosThreadingTools.dll";

            Assembly a = Assembly.Load(an); // net472 succeeds. net5 fails.
        }

#if NETCOREAPP
        private static Assembly ALC_Resolving(AssemblyLoadContext arg1, AssemblyName arg2)
        {
            if (!string.IsNullOrEmpty(arg2.CodeBase)) // net5 sees this as null
            {
                return arg1.LoadFromAssemblyPath(arg2.CodeBase);
            }

            return null;
        }
#endif
    }
}

Author:	AArnott
Assignees:	-
Labels:	area-AssemblyLoader-coreclr, untriaged
Milestone:	-

[jkotas]

#7752 has some context

[AArnott]

Thanks for the context. I get that .NET Core wants to diverge in assembly load behavior from Framework. I would like to see the Codebase property preserved in the Resolving event just so an app can choose to re-implement Framework behavior. Right now, it appears to be impossible.

[agocke]

We now have precedent from ProcessorArchitecture that we don't preserve obsolete information moving through AssemblyName. CodeBase is in the same category. Closing as Won't Fix.