无法解析类型为 Microsoft Extensions Configuration IConfiguration 的服务

Question

我收到这个错误，我一辈子都无法理解。

在尝试激活 'Microsoft.FeatureManagement.ConfigurationFeatureSettingsProvider' 时无法解析类型 'Microsoft.Extensions.Configuration.IConfiguration' 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. Microsoft.FeatureManagement

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拔毛之后。

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 也可以达到目的。使用 var 声明配置会产生问题。使用 IConfiguration 而不是 var。然后问题又消失了。

Answer 2

很抱歉将此评论作为答案，但如果您在新项目中使用上面的代码，请小心。它仍然进入根目录进行搜索，当您有 2 个具有相同 application.Environment.json

的项目时可能会导致问题

var configuration = new ConfigurationBuilder().AddJsonFile("appsettings.json").Build();