[Wasm] Add .NET 5 interpreter support

[jeromelaban]

The bootstrapper is now yet compatible with .NET5 target frameworks, as the mono CI does not bundle the proper libraries.

This issue is about adding support for .NET 5 runtime support for the interpreter only.

[tomasfabian]

Is this issue also relevant for .netstandard2.1 apps? I tried to apply it for a Blazor 3.2 WebAssembly app, but the Uno.Wasm.Bootstrap assembly wasn't loaded by the browser (I also tried Ctrl+Shift+R)

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netstandard2.1</TargetFramework>
    <RazorLangVersion>3.0</RazorLangVersion>

    <MonoWasmRuntimeConfiguration>threads-release</MonoWasmRuntimeConfiguration>
  </PropertyGroup>

  <PropertyGroup Condition="'$(Configuration)'=='Debug'">
    <MonoRuntimeDebuggerEnabled>true</MonoRuntimeDebuggerEnabled>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly" Version="3.2.0" />
    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.Build" Version="3.2.0" PrivateAssets="all" />
    <PackageReference Include="Microsoft.AspNetCore.Components.WebAssembly.DevServer" Version="3.2.0" PrivateAssets="all" />
    <PackageReference Include="System.Net.Http.Json" Version="3.2.1" />
  </ItemGroup>

  <ItemGroup>
    <PackageReference Include="Uno.Wasm.Bootstrap" Version="1.3.0-dev.42" />
    <PackageReference Include="Uno.Wasm.Bootstrap.DevServer" Version="1.3.0-dev.42" PrivateAssets="all" />
  </ItemGroup>

  <!--<PropertyGroup Condition="'$(Configuration)'=='Debug'">
    <DebugType>portable</DebugType>
    <DebugSymbols>true</DebugSymbols>
  </PropertyGroup>

  <PropertyGroup Condition="'$(Configuration)'=='Debug'">
    <DefineConstants>$(DefineConstants);TRACE;DEBUG</DefineConstants>
  </PropertyGroup>-->

</Project>

Chrome versions is: Version 83.0.4103.97 (Official Build) (64-bit)

The Run method from this example webassembly-threading-in-net throws an error:
System.NotSupportedException: Cannot start threads on this runtime.

[jeromelaban]

Thanks @tomasfabian. Could you provide the full error you're getting ?

[tomasfabian]

of course, this is from the VS output, is it good enough?:

_System.NotSupportedException: Cannot start threads on this runtime.
at (wrapper managed-to-native) System.Threading.Thread.Thread_internal(System.Threading.Thread,System.MulticastDelegate)
at System.Threading.Thread.StartInternal (System.Object principal, System.Threading.StackCrawlMark& stackMark) <0x30f0290 + 0x00008> in :0
at System.Threading.Thread.Start (System.Threading.StackCrawlMark& stackMark) <0x30f0128 + 0x0004e> in :0
at System.Threading.Thread.Start () <0x30eff70 + 0x0000e> in :0
at Joker.BlazorApp.Sample.Program.RunAsync () [0x00065] in C:\Users\tomas.fabian\source\repos\Joker.BlazorApp.Sample\Joker.BlazorApp.Sample\Program.cs:89
at Joker.BlazorApp.Sample.Program.Main (System.String[] args) [0x000b3] in C:\Users\tomas.fabian\source\repos\Joker.BlazorApp.Sample\Joker.BlazorApp.Sample\Program.cs:196
at Microsoft.AspNetCore.Components.WebAssembly.Hosting.EntrypointInvoker.InvokeEntrypoint (System.String assemblyName, System.String[] args) <0x2df00c0 + 0x0012c> in :0_

[jeromelaban]

This looks like an issue with the runtime not being able to create threads, rather than the bootstrapper itself. Do you need to create a thread for your app, or is it just for testing ? Threading is still a work in progress at this point.

[tomasfabian]

I wanted to solve my threading issue with a StackExchange.Redis. It creates a thread underneath, I'm not able to change it... and I found this interesting Uno package.
Will Uno package be able to solve these issues in general, or should I contact the library contributors or the Blazor team? This can happen with other .Net Standard libs, too.
Thank you for your interest @jeromelaban!

[jeromelaban]

Fixed by unoplatform/Uno.Wasm.Bootstrap#288