Build error on UWP form ARM 32 with an external dll and an async function

Unity Engine
, ,
1

Hello

We have an issue when building for UWP - ARM32 (Hololens2)
We have a dll with async functions like this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Runtime.InteropServices;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace TestClassLib
{
    public class TestClass1
    {
        private readonly HttpClient _httpClient = new HttpClient();

      
        public async Task<int> GetDotNetCountAsync()
        {
            // Suspends GetDotNetCount() to allow the caller (the web server)
            // to accept another request, rather than blocking on this one.
            var html = await _httpClient.GetStringAsync("https://dotnetfoundation.org");

            return Regex.Matches(html, @"\.NET").Count;
        }

        public int GetDotNetCount()
        {
          

            return GetDotNetCountAsync().Result;
        }


    }
}

It’s compiled for ARM 32/Release. In an unity script if we call the synchrone function everythings works, but if we await on the async function over the dll boundary the build breaks.

#if UNITY_WSA && !UNITY_EDITOR
TestClass1 t = new TestClass1();
int n = t.GetDotNetCount(); //this works

int n2 = await t.GetDotNetCountAsync(); //this breaks the build
#endif

Build error is error CS1705: Assembly ‘ClassLib’ with identity ‘ClassLib, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null’ uses ‘System.Runtime, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’ which has a higher version than referenced assembly ‘System.Runtime’ with identity ‘System.Runtime, Version=4.1.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a’

Any clue would be welcome. Thanks for reading

2

Looks like your precompiled ClassLib is compiled against wrong version of .NET. You should compiling against .NET Standard 2.0 or .NET Standard 2.1 if you want to use it in Unity.