![](/img/trans.png)
[英]System.InvalidOperationException: The current type, Microsoft.Extensions.Configuration.IConfiguration, is an interface and cannot be constructed
[英]“InvalidOperationException: No service for type 'Microsoft.Extensions.Configuration.IConfiguration' has been registered.”
我是编程的新手,还是c#和.NET Core的新手。
我在尝试确定为什么这个简单的“ hello world”应用程序因标题错误而失败时遇到了一些困难。
我正在尝试让应用程序读取“ Hello !!”。 从appsettings.json并将其显示在屏幕上。
这是我的Startup.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Configuration;
namespace My_NET_Core_Test_2
{
public class Startup
{
// This method gets called by the runtime. Use this method to add services to the container.
// For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
public void ConfigureServices(IServiceCollection services)
{
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app,
IHostingEnvironment env,
ILoggerFactory loggerFactory,
IConfiguration configuration)
{
loggerFactory.AddConsole();
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.Run(async (context) =>
{
var greeting = configuration["Greeting"];
await context.Response.WriteAsync(greeting);
});
}
}
}
这是我的Program.cs:
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Hosting;
namespace My_NET_Core_Test_2
{
public class Program
{
public static void Main(string[] args)
{
var host = new WebHostBuilder()
.UseKestrel()
.UseContentRoot(Directory.GetCurrentDirectory())
.UseIISIntegration()
.UseStartup<Startup>()
.UseApplicationInsights()
.Build();
host.Run();
}
}
}
这是我的appsettings.json:
{
"Greeting": "Hello!!",
"ConnectionStrings": {
"DefaultConnection": "Server=(localdb)\\MSSQLLocalDB;Database=_CHANGE_ME;Trusted_Connection=True;MultipleActiveResultSets=true"
}
}
感谢您的协助!
由于无法解决IConfiguration实例,因此会出现此问题。 您可以通过ConfigurationBuilder在Startup构造函数中定义实例,该实例让您定义应从何处获取配置值。
这是一个基本示例,其中ConfigurationBuilder将从内容根路径中的appsettings.json读取值并读取环境变量。
public class Startup
{
private readonly IConfiguration _configuration;
public Startup(IHostingEnvironment env)
{
var builder = new ConfigurationBuilder()
.SetBasePath(env.ContentRootPath)
.AddJsonFile($"appsettings.json", optional: false, reloadOnChange: true)
.AddEnvironmentVariables();
_configuration = builder.Build();
}
// This method gets called by the runtime. Use this method to add services to the container.
// For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
public void ConfigureServices(IServiceCollection services)
{
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app,
IHostingEnvironment env,
ILoggerFactory loggerFactory)
{
loggerFactory.AddConsole();
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
app.Run(async (context) =>
{
var greeting = _configuration["Greeting"];
await context.Response.WriteAsync(greeting);
});
}
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.