C# 从Core 2.0中的类库访问appsettings.json中的设置

我在这里读了十几个问题，至少有4篇博文，但我无法在VS2017解决方案中使用多个类库项目。然而，我可以让它与一个web应用程序和一个类库的解决方案一起工作，尽管使用的模式与我在文档中找到的模式不同，等等

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

我的解决方案包含5个项目：Web应用程序、测试、基础设施、服务、域（后三个是类库）

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

在基础设施项目中，我创建了一个名为EmailConfigurationSettings的类，并将其注册到WebApp的StartUp类中

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

此类位于类库中：

public class EmailConfigurationSettings
{
    public string Provider { get; set; }
    public string Username { get; set; }
    public string Password { get; set; }
}

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

这在WebApp的StartUp.cs中：

services.Configure<EmailConfigurationSettings>(Configuration.GetSection("EmailConfigurationSettings"));
services.AddOptions();

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

我需要服务项目中的设置。但现在我只是想确保我能真正找回它们。下面的代码遵循我找到的所有代码示例，但生成：

public class LoadEmailSettingsFromAppSettings
{
    private readonly IOptions<EmailConfigurationSettings> _emailSettings;

    public LoadEmailSettingsFromAppSettings(IOptions<EmailConfigurationSettings> emailSettings)
    {
        _emailSettings = emailSettings;
        Message = "Our provider is " + _emailSettings.Value.Provider;
    }

    public string Message { get; set; }
}

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

公共类加载EmailSettingsFromAppSettings
{
专用只读IOPS\u电子邮件设置；
公共加载电子邮件设置RomappSettings（IOOptions电子邮件设置）
{
_emailSettings=emailSettings；
Message=“我们的提供商是”+\u emailSettings.Value.provider；
}
公共字符串消息{get；set；}
}

_emailSettings始终为空

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

所以我试着在TestProject中测试它：

IOptions<EmailConfigurationSettings> someOptions = Options.Create<EmailConfigurationSettings>(new EmailConfigurationSettings());

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

IOptions someOptions=Options.Create（新建EmailConfigurationSettings（））；

嗯，那也是空的

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

在另一个解决方案中，使用WebApp和一个类库的解决方案， 使用我在其中一个博客上发现的稍微不同的模式，我实际上可以从appsettings.json检索值：

public class AuthMessageSender : IEmailSender, ISmsSender
{
    public AuthMessageSender(IOptions<EmailConfig> emailSettings)
    {
        _emailSettings = emailSettings.Value;
    }

    public EmailConfig _emailSettings { get; }

    public Task SendEmailAsync(string email, string subject, string message)
    {
        Execute(email, subject, message).Wait();
        return Task.FromResult(0);
    }

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

公共类AuthMessageSender:IEmailSender，ISmsSender
{
公共AuthMessageSender（IOptions emailSettings）
{
_emailSettings=emailSettings.Value；
}
公共EmailConfig_emailSettings{get；}
公共任务SendEmailAsync（字符串电子邮件、字符串主题、字符串消息）
{
执行（电子邮件、主题、消息）。等待（）；
返回Task.FromResult（0）；
}

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

请注意，IOptions类与9个属性不同，但构造方式与上面的模式相同

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

但是使用这种模式在多类库项目中不起作用。我如何理解如何在多类库场景中使用这种模式

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

---

我不知道为什么他们放弃了ConfigurationManager，这要容易得多。

在微服务中，您可以简单地绑定到与json定义匹配的新对象。您也可以这样做

var emailConfig = new EmailConfigurationSettings();
Configuration.GetSection("EmailConfigurationSettings").Bind(emailConfig);
services.AddSingleton(emailConfig);

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

一旦你这样做了，你所要做的就是在你的服务层构造函数中请求一份EmailConfigurationSettings的副本。这将给你该对象的依赖注入单例

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

---

我会在“绑定”上设置一个断点，并确保填充了电子邮件配置。

这里有一个关于类库的有趣答案：

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

在代码的这一部分中：

private readonly IOptions<EmailConfigurationSettings> _emailSettings;

public LoadEmailSettingsFromAppSettings(IOptions<EmailConfigurationSettings> emailSettings)
{
    _emailSettings = emailSettings;         

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

private readonly IOptions\u emailSettings；
公共加载电子邮件设置RomappSettings（IOOptions电子邮件设置）
{
_emailSettings=emailSettings；

依赖项注入不起作用，因为您在类库中，所以应该保持这种方式

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

在Web应用程序的某个地方，您可以构建LoadEmailSettingsFromAppSettings

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

公共类SomeClass
{
public SomeClass（IOptions emailSettings）//依赖项注入在您的webapp中工作
{
var loadEmail=new LoadEmailSettingsFromAppSettings（emailSettings）；//将emailSettings发送到类库中的其他类
//(...)
}
}

而私有只读应为：

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

public IOptions<EmailConfigurationSettings> EmailSettings {get; private set;}

public-IOptions-EmailSettings{get；private-set；}

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}

---

我希望运行项目a在AddSingleton调用（在StartUp.cs中）上设置一个断点是清楚和有帮助的产生一个空的emailConfig。所以这不起作用，与OP方法一样。如果这产生一个空的结果，那么他没有正确加载他的应用程序配置。这段代码取自我的个人mvc应用程序，所以我知道它可以工作。如果你将一个变量设置为getsection的返回值，我会认为它返回空

public class SomeClass
{
    public SomeClass(IOptions<EmailConfigurationSettings> emailSettings) // dependency injection works in your webapp
    {
        var loadEmail = new LoadEmailSettingsFromAppSettings(emailSettings); // send EmailSettings to your other class in your class library

        //(...)
    }
}