Cannot create an XmlSerializer of a type defined in a script

[aelij]

Version Used: 2.3.2 (VS 15.4)

Steps to Reproduce:

In C# Interactive:

#r "System.Xml"
class X { }
new System.Xml.Serialization.XmlSerializer(typeof(X))

Expected Behavior:
Return an XmlSerializer.

Actual Behavior:

The filename, directory name, or volume label syntax is incorrect. (Exception from HRESULT: 0x8007007B)
  + System.Runtime.InteropServices.Marshal.ThrowExceptionForHRInternal(int, System.IntPtr)
  + Microsoft.Win32.Fusion.ReadCache(System.Collections.ArrayList, string, uint)
  + System.Reflection.RuntimeAssembly.EnumerateCache(System.Reflection.AssemblyName)
  + System.Reflection.RuntimeAssembly.LoadWithPartialNameInternal(System.Reflection.AssemblyName, System.Security.Policy.Evidence, ref System.Threading.StackCrawlMark)
  + System.Reflection.Assembly.LoadWithPartialName(string, System.Security.Policy.Evidence)
  + System.Xml.Serialization.TempAssembly.LoadGeneratedAssembly(System.Type, string, out System.Xml.Serialization.XmlSerializerImplementation)
  + System.Xml.Serialization.XmlSerializer..ctor(System.Type, string)
  + System.Xml.Serialization.XmlSerializer..ctor(System.Type)

Analysis:
I believe the issue is that generated assembly name for script assemblies contains an invalid character for the file system (#), and when the serializer attempts to load a serialization assembly, it fails.

roslyn/src/Scripting/Core/ScriptBuilder.cs

Line 55 in 2b7c615

_assemblyNamePrefix = s_globalAssemblyNamePrefix + "#" + Interlocked.Increment(ref s_engineIdDispenser).ToString();

[jcouv]

Tagging @tmat

[andrew-vdb]

Any workaround for this?

[tmat]

I believe the issue is that generated assembly name for script assemblies contains an invalid character for the file system (#)

# is perfectly valid file name character.

[aelij]

@tmat I was mistaken, the problem was the * in the assembly name:

roslyn/src/Scripting/Core/ScriptBuilder.cs

Line 53 in b4cad27

s_globalAssemblyNamePrefix = "\u211B*" + Guid.NewGuid().ToString();

I've added a test to the PR.

[tmat]

This is a bug in XmlSerializer. I'm fine with implementing a workaround and omitting * from the assembly name since it's unlikely that the issue in XmlSerializer in .NET Framework will be fixed.

[tmat]

What's the scenario for which XML serialization of types defined in a script is needed?

[uholeschak]

Is there already a workaround for this?