In TFM net 5.0 i have a console app that has the setup as below code:

• I dont understand why i get exception "System.ArgumentNullException: 'Value cannot be null. (Parameter 'services')'" when running the app.
• Why does the exception refer to "services"?
• Why cant i add AddOtions(): to serviceCollection?

namespace funkyNamespace
{
    public class Program
    {
        public static IConfigurationRoot configuration;
        private static IServiceCollection serviceCollection;


        public static void Main()
        {
             ConfigureServices(serviceCollection);
            MainAsync(log).GetAwaiter().GetResult();
        }

        private static async Task MainAsync()
        {
           //....business logic is here
        }
       static void ConfigureServices(IServiceCollection       serviceColletion)
        {
            serviceColletion.AddOptions();


            var serviceBuilder = serviceColletion.BuildServiceProvider();


            configuration = new ConfigurationBuilder()
                .SetBasePath(Directory.GetParent(AppContext.BaseDirectory).FullName)
                .AddJsonFile("local.settings.json", false)
                .Build();

            var section = configuration.GetSection("Values");
            serviceColletion.AddMemoryCache();
           ....
           ....
        }
    }
}

CodePudding user response：

You need to instantiate the service collection first. For example in the field initializer:

 private static IServiceCollection serviceCollection = new ServiceCollection();

Also there are some other issues with your code:

• Probably you want to store result of serviceColletion.BuildServiceProvider(); in a field (or maybe even the "root" service or even not storing anything - just using the build "root" service), not the collection itself (note that calling BuildServiceProvider multiple time is highly discouraged)
• You are adding services to the collection after building the provider - so they will not be present in the build one.

CodePudding user response：

You don't return anything to your servicecollection.

First I would change:

static void ConfigureServices(IServiceCollection serviceColletion)

to

static void ConfigureServices(this IServiceCollection serviceColletion)

Then change:

ConfigureServices(serviceCollection);

to

serviceCollection.ConfigureServices();

A complete answer:

namespace funkyNamespace
{
    public class Program
    {
        public static IConfigurationRoot configuration;
        private static IServiceCollection serviceCollection;


        public static void Main()
        {
            serviceCollection.ConfigureServices();
            MainAsync(log).GetAwaiter().GetResult();
        }

        private static async Task MainAsync()
        {}

        static void ConfigureServices(this IServiceCollection serviceColletion)
        {
            serviceColletion.AddOptions();


            var serviceBuilder = serviceColletion.BuildServiceProvider();


            configuration = new ConfigurationBuilder()
                .SetBasePath(Directory.GetParent(AppContext.BaseDirectory).FullName)
                .AddJsonFile("local.settings.json", false)
                .Build();

            var section = configuration.GetSection("Values");
            serviceColletion.AddMemoryCache();
           ....
          }
    }
}