Build C# project process does not copy dependency assemblies to output folder

Question

I am testing a code targeting .NET standard 2.0, in Visual Studio 2022. The code depends on Polly and Microsoft.Extensions.Http.Polly. The program fails to start with error message :

Unhandled Exception: System.IO.FileNotFoundException: Could not load file or assembly 'Polly, Version=7.0.0.0, Culture=neutral, PublicKeyToken=c8a3ffc3f8f825cc' or one of its dependencies. The system cannot find the file specified.

I found that the error occurred because the build project process does not copy the Polly.dll to folder NetRetry\bin\Debug\netstandard2.0. But why are these assemblies not copied to output folder? I can find these assemblies in .nuget\packages folder.

---

To reproduce this error

Program.cs

using Microsoft.Extensions.Http;
using Polly;
using System;
using System.Net.Http;
using System.Threading;

class Program
{
    static void Main(string[] args)
    {
        var h = Policy
            .HandleResult<HttpResponseMessage>(r => r.StatusCode != System.Net.HttpStatusCode.OK)
            .Or<Exception>()
            .RetryAsync(3, (r, count) =>
                {
                    Console.WriteLine($"Log retry {count}");
                    r.Result.Dispose();
                });

        var handler = new PolicyHttpMessageHandler(h);
        handler.InnerHandler = new HttpClientHandler();

        HttpClient c = new HttpClient(handler);
        var result = c.GetAsync("https://www.google.com/non-existing", CancellationToken.None).ConfigureAwait(false).GetAwaiter().GetResult();
    }
}

NetRetry.csproj

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

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFrameworks>netstandard2.0</TargetFrameworks>
    <AutoGenerateBindingRedirects>True</AutoGenerateBindingRedirects>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.Http.Polly" Version="6.0.3" />
    <PackageReference Include="Polly" Version="7.2.3" />
  </ItemGroup>

</Project>

---

I tried retargeting project to .NET 5.0 and build the project. This time the assemblies are all copied to folder NetRetry\bin\Debug\net5.0, and the program runs normally.

Answer 1

Manually enable CopyLocalLockFileAssemblies will solve this.

Add to PropertyGroup

    <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>