Blazor .NET Core 3 Preview Compile Error - Visual Studio 2019 Preview

Question

I am currently unable to compile my Blazor application using .NET Core 3 Preview and Visual Studio 2019 Preview (Latest Version, just downloaded)

I have only created a few files.

MainLayoutModel.cs (In Shared Folder)


using Microsoft.AspNetCore.Components;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace ICSSNetwork
{
    public class MainLayoutModel : LayoutComponentBase
    {
        [Inject] protected AppState AppState { get; set; }

        protected async Task Logout()
        {
            await AppState.Logout();
        }
    }
}

LoginDetails.cs (Project Root)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace ICSSNetwork
{
    public class LoginDetails
    {
        public string Username { get; set; }
        public string Password { get; set; }
    }
}

AppState.cs (Project Root)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
using System.Threading.Tasks;
using System.Web.Helpers;

namespace ICSSNetwork
{
    public class AppState
    {
        private readonly HttpClient _httpClient;
      //  private readonly ILocalStorage _localStorage;

        public bool IsLoggedIn { get; private set; }

        public AppState(HttpClient httpClient)
                       // ILocalStorage localStorage)
        {
            _httpClient = httpClient;
            //_localStorage = localStorage;
        }

        public async Task Login(LoginDetails loginDetails)
        {
            //var response = await _httpClient.PostAsync(Urls.Login, new StringContent(Json.Serialize(loginDetails), Encoding.UTF8, "application/json"));

            if (loginDetails.Password == "TEST123")
            {
                //await SetAuthorizationHeader();

                IsLoggedIn = true;
            }
        }

        public async Task Logout()
        {
            //await _localStorage.RemoveItem("authToken");
            IsLoggedIn = false;
        }

        //private async Task SaveToken(HttpResponseMessage response)
        //{
        //    var responseContent = await response.Content.ReadAsStringAsync();
        //    var jwt = Json.Deserialize<JwToken>(responseContent);

        //    await _localStorage.SetItem("authToken", jwt.Token);
        //}

        //private async Task SetAuthorizationHeader()
        //{
        //    if (!_httpClient.DefaultRequestHeaders.Contains("Authorization"))
        //    {
        //        var token = await _localStorage.GetItem<string>("authToken");
        //        _httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
        //    }
        //}
    }
}

I built my project when I first created it and it built fine. After adding these files I am getting the following build error:

Error MSB3073 The command "dotnet "C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.blazor.mono\3.0.0-preview8.19380.1\build\netstandard1.0\../../tools/illink/illink.dll" -l none --disable-opt unreachablebodies --verbose --strip-security true --exclude-feature com --exclude-feature sre -v false -c link -u link -b true -d "C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.blazor.mono\3.0.0-preview8.19380.1\build\netstandard1.0\../../tools/mono/bcl/" -d "C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.blazor.mono\3.0.0-preview8.19380.1\build\netstandard1.0\../../tools/mono/bcl/Facades/" -o "C:\Users\adamc\Desktop\ICSSNetworkManager\ICSSNetwork\ICSSNetwork\obj\Debug\netstandard2.0\blazor\linker/" -x "C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.blazor.build\3.0.0-preview8.19405.7\targets\BuiltInBclLinkerDescriptor.xml" -x "C:\Users\adamc\Desktop\ICSSNetworkManager\ICSSNetwork\ICSSNetwork\obj\Debug\netstandard2.0\blazor\linker.descriptor.xml" -a "C:\Users\adamc\.nuget\packages\blazored.localstorage\2.0.12\lib\netstandard2.0\Blazored.LocalStorage.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnet.razor\3.2.7\lib\net45\System.Web.Razor.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnet.webpages\3.2.7\lib\net45\System.Web.Helpers.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnet.webpages\3.2.7\lib\net45\System.Web.WebPages.Deployment.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnet.webpages\3.2.7\lib\net45\System.Web.WebPages.Razor.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnet.webpages\3.2.7\lib\net45\System.Web.WebPages.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.authorization\3.0.0-preview8.19405.7\lib\netstandard2.0\Microsoft.AspNetCore.Authorization.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.blazor\3.0.0-preview8.19405.7\lib\netstandard2.0\Microsoft.AspNetCore.Blazor.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.blazor.httpclient\3.0.0-preview8.19405.7\lib\netstandard2.0\Microsoft.AspNetCore.Blazor.HttpClient.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.components\3.0.0-preview8.19405.7\lib\netstandard2.0\Microsoft.AspNetCore.Components.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.components.web\3.0.0-preview8.19405.7\lib\netstandard2.0\Microsoft.AspNetCore.Components.Web.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.metadata\3.0.0-preview8.19405.7\lib\netstandard2.0\Microsoft.AspNetCore.Metadata.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.bcl.asyncinterfaces\1.0.0-preview8.19405.3\lib\netstandard2.0\Microsoft.Bcl.AsyncInterfaces.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.extensions.dependencyinjection\3.0.0-preview8.19405.4\lib\netstandard2.0\Microsoft.Extensions.DependencyInjection.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.extensions.dependencyinjection.abstractions\3.0.0-preview8.19405.4\lib\netstandard2.0\Microsoft.Extensions.DependencyInjection.Abstractions.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.extensions.logging.abstractions\3.0.0-preview8.19405.4\lib\netstandard2.0\Microsoft.Extensions.Logging.Abstractions.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.extensions.options\3.0.0-preview8.19405.4\lib\netstandard2.0\Microsoft.Extensions.Options.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.extensions.primitives\3.0.0-preview8.19405.4\lib\netstandard2.0\Microsoft.Extensions.Primitives.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.jsinterop\3.0.0-preview8.19405.4\lib\netstandard2.0\Microsoft.JSInterop.dll" -a "C:\Users\adamc\.nuget\packages\microsoft.web.infrastructure\1.0.0\lib\net40\Microsoft.Web.Infrastructure.dll" -a "C:\Users\adamc\.nuget\packages\mono.webassembly.interop\3.0.0-preview8.19405.4\lib\netstandard2.0\Mono.WebAssembly.Interop.dll" -a "C:\Program Files\dotnet\sdk\NuGetFallbackFolder\system.buffers\4.5.0\lib\netstandard2.0\System.Buffers.dll" -a "C:\Users\adamc\.nuget\packages\system.componentmodel.annotations\4.6.0-preview8.19405.3\lib\netstandard2.0\System.ComponentModel.Annotations.dll" -a "C:\Users\adamc\.nuget\packages\system.memory\4.5.3\lib\netstandard2.0\System.Memory.dll" -a "C:\Program Files\dotnet\sdk\NuGetFallbackFolder\system.numerics.vectors\4.5.0\lib\netstandard2.0\System.Numerics.Vectors.dll" -a "C:\Users\adamc\.nuget\packages\system.runtime.compilerservices.unsafe\4.6.0-preview8.19405.3\lib\netstandard2.0\System.Runtime.CompilerServices.Unsafe.dll" -a "C:\Users\adamc\.nuget\packages\system.text.encodings.web\4.6.0-preview8.19405.3\lib\netstandard2.0\System.Text.Encodings.Web.dll" -a "C:\Users\adamc\.nuget\packages\system.text.json\4.6.0-preview8.19405.3\lib\netstandard2.0\System.Text.Json.dll" -a "C:\Users\adamc\.nuget\packages\system.threading.tasks.extensions\4.5.2\lib\netstandard2.0\System.Threading.Tasks.Extensions.dll" -a "C:\Users\adamc\Desktop\ICSSNetworkManager\ICSSNetwork\ICSSNetwork\obj\Debug\netstandard2.0\ICSSNetwork.dll"" exited with code -532462766. ICSSNetwork C:\Users\adamc\.nuget\packages\microsoft.aspnetcore.blazor.build\3.0.0-preview8.19405.7\targets\Blazor.MonoRuntime.targets 441

Anyone have any idea as to what may be causing this? Is it a bug with the .NET Core 3 Preview?

Is there some additional output when executing "dotnet build" on the command line? — Christian Klemm
@ChristianKlemm Managed to get this Unhandled Exception: Mono.Cecil.AssemblyResolutionException: Failed to resolve assembly: 'System.Web, Version=4.0.0.0, Culture=neutral Seems it can't resolve System.Web but I don't see why. — Adam Creed
It's odd that you have a reference to System.Web. Do you added an explicit reference to it somewhere? Or did you install some additional NuGet packages? — Christian Klemm
@ChristianKlemm I added one additional NuGet Package (Blazored.LocalStorage) but nothing about System.Web. I also checked my references and System.Web is not listed. I am thinking this is a bug in the preview as I can't think of anything else. — Adam Creed

Christian Klemm Christian Klemm · Accepted Answer · 2019-08-25T23:51:38

In your AppState.cs you have the using statement using System.Web.Helpers;. The System.Web Namespace was used in ASP.NET and has been abandoned for ASP.NET Core.

I just created a fresh Blazor Wasm project (however this should also work using Blazor Serverside, not sure which one you're using) and pasted your AppState class. The namespace System.Web.Helpers cannot be found, neither can the class LoginDetails. You might want to double check all your references and NuGet packages because I'm quite sure that one adds the namespace System.Web.Helpers and references System.Web which is not available on .NET Core.

Blazor .NET Core 3 Preview Compile Error - Visual Studio 2019 Preview

1 Answers