I found a way that can load all hostingStartupAssemblies with dependencies

[1257960069]

using System.Reflection;
using Admin.NET.Core;
using Microsoft.Extensions.DependencyModel;

class Program
{
    static Program()
    {
        var hostingStartupAssembliesFromDeps = DependencyContext.Default
            .GetDefaultAssemblyNames()
            .Select(Assembly.Load)
            .Where(assembly => assembly.GetCustomAttributes<HostingStartupAttribute>().Any())
            .Select(assembly => assembly.GetName().Name)
            .Where(name => !name.StartsWith("Microsoft"));

        var hostingStartupAssemblies = $"{Environment.GetEnvironmentVariable("ASPNETCORE_HOSTINGSTARTUPASSEMBLIES")};{string.Join(";", hostingStartupAssembliesFromDeps)}";
        Environment.SetEnvironmentVariable("ASPNETCORE_HOSTINGSTARTUPASSEMBLIES", hostingStartupAssemblies);
    }
}

[mythz]

Cool, what use-case would you use this for?

[1257960069]

Configure startup classes for modular development can work in any project, not just in entry projects. There is also no need to configure environment variables to discover relevant assembly。

[1257960069]

if ProjectA depend on ProjectB。ProjectB depend ProjectC，ProjectC has a IHostingStarup class。 this class can not be call when run app， if not set ASPNETCORE_HOSTINGSTARTUPASSEMBLIES at ProjectA