Can different versions of the "same" assembly be loaded at the same time in .NET 6?
app is the app, which uses either Assembly.LoadFrom() or
AssemblyLoadContext to load an assembly. It attempts to load each assembly
specified on the command-line, then find and execute the method
Example.MyType.Print() from the assembly:
% dotnet app/bin/Debug/net6.0/multi-versions.dll …
Lib.cs is the source code to the library to load, specifying a public
static method Example.MyType.Print().
lib-v1 builds Lib.cs with V1 defined, and $(Version)=1.0.0.0.
% monodis --assembly lib-v1/bin/Debug/net6.0/lib.dll
Assembly Table
Name: lib
Hash Algoritm: 0x00008004
Version: 1.0.0.0
Flags: 0x00000000
PublicKey: BlobPtr (0x00000000)
Zero sized public key
Culture:
lib-v2 builds Lib.cs with V2 defined, and $(Version)=2.0.0.0.
% monodis --assembly lib-v2/bin/Debug/net6.0/lib.dll
Assembly Table
Name: lib
Hash Algoritm: 0x00008004
Version: 2.0.0.0
Flags: 0x00000000
PublicKey: BlobPtr (0x00000000)
Zero sized public key
Culture:
Can It Run? Not with Assembly.LoadFrom():
% make all
% make run
dotnet app/bin/Debug/net6.0/app.dll lib-v1/bin/Debug/net6.0/lib.dll lib-v2/bin/Debug/net6.0/lib.dll
v1
Unhandled exception. System.IO.FileLoadException: Assembly with same name is already loaded
at System.Runtime.Loader.AssemblyLoadContext.LoadFromPath(IntPtr ptrNativeAssemblyLoadContext, String ilPath, String niPath, ObjectHandleOnStack retAssembly) in System.Private.CoreLib.dll:token 0x6003a0b+0x2e
at System.Runtime.Loader.AssemblyLoadContext.LoadFromAssemblyPath(String assemblyPath) in System.Private.CoreLib.dll:token 0x6003a45+0x48
at System.Reflection.Assembly.LoadFrom(String assemblyFile) in System.Private.CoreLib.dll:token 0x6004ffa+0x74
at App.Main(String[] args) in /Users/jon/Documents/Developer/tmp/multi-versions/app/Program.cs:line 25
make: *** [run] Abort trap: 6
It can run with AssemblyLoadContext:
% make run STYLE=Context
dotnet app/bin/Debug/net6.0/app.dll true lib-v1/bin/Debug/net6.0/lib.dll lib-v2/bin/Debug/net6.0/lib.dll
v1
v2
It fails when using AssemblyLoadContext.Default.LoadFromAssemblyPath():
% make run STYLE=DefaultContext
dotnet app/bin/Debug/net6.0/app.dll DefaultContext lib-v1/bin/Debug/net6.0/lib.dll lib-v2/bin/Debug/net6.0/lib.dll
v1
Unhandled exception. System.IO.FileLoadException: Assembly with same name is already loaded
at System.Runtime.Loader.AssemblyLoadContext.LoadFromPath(IntPtr ptrNativeAssemblyLoadContext, String ilPath, String niPath, ObjectHandleOnStack retAssembly) in System.Private.CoreLib.dll:token 0x6003a0b+0x2e
at System.Runtime.Loader.AssemblyLoadContext.LoadFromAssemblyPath(String assemblyPath) in System.Private.CoreLib.dll:token 0x6003a45+0x48
at App.Load(AssemblyLoad how, String path) in /Users/jon/Documents/Developer/tmp/multi-versions/app/Program.cs:line 35
at App.Main(String[] args) in /Users/jon/Documents/Developer/tmp/multi-versions/app/Program.cs:line 19
make: *** [run] Abort trap: 6