无法解析 Microsoft 扩展配置 IConfiguration 类型的服务

Question

我收到此错误，一生无法理解。

尝试激活“Microsoft.FeatureManagement.ConfigurationFeatureSettingsProvider”时无法解析“Microsoft.Extensions.Configuration.IConfiguration”类型的服务。

这是一个简单的 .net core 2.2 控制台应用程序，添加了以下 nuget 包。

1. Microsoft.Extensions.Configuration.Json
2. Microsoft.Extensions.DependencyInjection
3. 微软功能管理

using System;
using System.Threading.Tasks;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.FeatureManagement;
using Microsoft.FeatureManagement.FeatureFilters;

namespace ConfigurationConsoleApp
{
    class Program
    {
        static async Task Main(string[] args)
        {
            const string FeatureName = "Beta";

            var configuration = new ConfigurationBuilder().AddJsonFile("appsettings.json").Build();
            var services = new ServiceCollection();
            services.AddSingleton(configuration).AddFeatureManagement().AddFeatureFilter<PercentageFilter>().AddFeatureFilter<AccountIdFilter>();
            var serviceProvider = services.BuildServiceProvider();
            var featureManager = serviceProvider.GetRequiredService<IFeatureManager>();
            var enabled = await featureManager.IsEnabledAsync(FeatureName);
            Console.WriteLine($"The {FeatureName} feature is {(enabled ? "enabled" : "disabled")} ");
        }
    }
}

// The following are the command for the packages.

dotnet add package Microsoft.Extensions.Configuration.Json --version 2.1.1
dotnet add package Microsoft.Extensions.DependencyInjection --version 2.1.1
dotnet add package Microsoft.FeatureManagement --version 2.0.0-preview-010610001-1263

Answer 1

好的，这是经过几个小时的头发拉扯。

services.AddSingleton(configuration).AddFeatureManagement().AddFeatureFilter<PercentageFilter>().AddFeatureFilter<AccountIdFilter>();

should be 

services.AddSingleton<IConfiguration>(configuration).AddFeatureManagement().AddFeatureFilter<PercentageFilter>().AddFeatureFilter<AccountIdFilter>();

注意泛型 <IConfiguration>

我还注意到，将配置对象声明为 IConfiguration 也可以解决问题。使用 var 声明配置会出现问题。而不是 var 使用IConfiguration。然后问题又消失了。