Question

我正在尝试遵循this example from Microsoft Docs来从ASP.NET Core 2.1应用程序中的appsettings.json文件中检索一些配置选项。

我上课了

public class MailServer
{
    public string Host { get; set; }
    public int Port { get; set; }
    public bool UseSSL { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
    public string FromAddress { get; set; }
    public MailServer()
    {
    }
}

转到Startup.cs中的配置

public void ConfigureServices(IServiceCollection services)
{
    // .....
    services.Configure<MailServer>(Configuration.GetSection("MailServer"));
    // .....
    services.AddSingleton<IScheduledTask, ScheduledTask>();
}

在启动时，我还添加了ScheduledTask作为单例，以便从该特定类访问上下文-这也是我要访问选项的地方。

public interface IScheduledTask
{
    void MonitorCloudHosts();
}

public class ScheduledTask : IScheduledTask
{
    private readonly IServiceProvider _ServiceProvider;
    private readonly MailServer _mailServer;

    // note here you ask to the injector for IServiceProvider
    public ScheduledTask(IServiceProvider serviceProvider, IOptions<MailServer> optionsAccessor)
    {
        _ServiceProvider = serviceProvider;
        _mailServer = optionsAccessor.Value;
    }

    public void MonitorCloudHosts()
    {
        // Do some stuff
        var xyz = _mailServer.Host;
    }
}

这是我的appsettings.json文件：

  {
    "Logging": {
      "LogLevel": {
        "Default": "Warning"
      }
    },
    "AllowedHosts": "*",
    "ConnectionStrings": {
      "CloudMonitorConnection": "Server=.\\SQLEXPRESS;Database=CloudMonitor;Integrated Security=SSPI;MultipleActiveResultSets=true;",
      "HangFireConnection": "Server=.\\SQLEXPRESS;Database=HangFire;Integrated Security=SSPI;"
    },
    "MailServer": {
      "Host": "smtp.gmail.com",
      "Port": "587",
      "UseSSL": "True",
      "Username": "xxxxxxx@gmail.com",
      "Password": "xxxxxxx",
      "FromAddress": "xxxxxxx<xxxxxxx@gmail.com>"
    }
  }

编译器在调用_mailServer.Host时显示错误，提示“需要对象引用...”-但是在optionsAccessor.Value上未显示错误。

optionsAccessor.Value是否应返回MailServer的实例？我在这里做菜鸟错误吗？

Answer 1

UseSSL类的属性MailServer为bool，但在appsettings.json中设置为"True"。

您应该像这样更改appsettings.json：

"MailServer": {
  "Host": "smtp.gmail.com",
  "Port": 587,
  "UseSSL": true,
  "Username": "xxxxxxx@gmail.com",
  "Password": "xxxxxxx",
  "FromAddress": "xxxxxxx<xxxxxxx@gmail.com>"
}

编辑：我用此代码创建了一个空项目，并将其编译。也许在使用语句时出错或启用了严格模式？

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace samp
{
    public class MailServer
    {
        public string Host { get; set; }
        public int Port { get; set; }
        public bool UseSSL { get; set; }
        public string Username { get; set; }
        public string Password { get; set; }
        public string FromAddress { get; set; }
        public MailServer()
        {
        }
    }

    public interface IScheduledTask
    {
        void MonitorCloudHosts();
    }

    public class ScheduledTask : IScheduledTask
    {
        private readonly IServiceProvider _ServiceProvider;
        private readonly MailServer _mailServer;

        // note here you ask to the injector for IServiceProvider
        public ScheduledTask(IServiceProvider serviceProvider, IOptions<MailServer> optionsAccessor)
        {
            _ServiceProvider = serviceProvider;
            _mailServer = optionsAccessor.Value;
        }

        public void MonitorCloudHosts()
        {
            // Do some stuff
            var xyz = _mailServer.Host;
        }
    }

    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
            services.Configure<MailServer>(Configuration.GetSection("MailServer"));
            services.AddSingleton<IScheduledTask, ScheduledTask>();
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseMvc();
        }
    }
}

ASP.NET Core 2.1-选项模式-访问选项不会返回绑定类的实例

1 个答案: