Error on published ASP.NET core site: Cannot find compilation library location for package 'Microsoft.AspNet.WebApi.Client'

Question

My webb app works fine when run from Visual Studio, but when I publish and try to load a page, I get:

InvalidOperationException: Cannot find compilation library location for package 'Microsoft.AspNet.WebApi.Client' Microsoft.Extensions.DependencyModel.CompilationLibrary.ResolveReferencePaths(ICompilationAssemblyResolver resolver, List assemblies)

I've been stuck on this for quite a while. I've attempted to apply the various workarounds in the thread https://github.com/dotnet/core-setup/issues/2981, but none of them have worked.

My csproj file is pasted below. I'm not sure what other information would be useful:

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

  <PropertyGroup>
    <TargetFramework>netcoreapp2.1</TargetFramework>
    <UserSecretsId>aspnet-CrowdQuery2-8C668DB3-5C80-4D9E-851D-2434D0CDA7E9</UserSecretsId>
    <PublishWithAspNetCoreTargetManifest>false</PublishWithAspNetCoreTargetManifest>
  </PropertyGroup>

  <PropertyGroup>
    <RuntimeFrameworkVersion>2.1.2</RuntimeFrameworkVersion>    
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.AspNet.WebApi.Client" Version="5.2.6" />
    <PackageReference Include="Microsoft.AspNetCore.App" />
    <PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="2.1.3" PrivateAssets="All" />
  </ItemGroup>

  <ItemGroup>
    <Folder Include="ViewModels\" />
  </ItemGroup>

</Project>

Answer 1

I've been having the same issue using Microsoft Azure.

The solution in this case was to clean up the wwwroot folder in our web app using Kudu (Development Tools -> Advanced Options), because there were some old DLLs still left from before the upgrade to .NET Core 2.1, because .NET Core 1 publishes the DLLs to the wwwroot folder, whereas in 2.1, the DLLs are loaded from a global store.

After having completely emptied the wwwroot folder, and redeploying the app, the error was resolved and the app ran as expected.