C# 如何在.NET Core中的启动类构造函数中访问AppSettings

我正在尝试添加SeriLog设置，比如min log level和从配置文件滚动文件路径。标准是这样硬编码：

public Startup(IHostingEnvironment env)
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
        .AddEnvironmentVariables();
    Configuration = builder.Build();

    Log.Logger = new LoggerConfiguration()
        .MinimumLevel.Debug()
        .WriteTo.RollingFile("C:/LogFiles/log-{Date}.txt")
        .CreateLogger();
}

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Is((LogEventLevel)Enum.Parse(typeof(LogEventLevel),
        Configuration.GetValue<string>("AppSettings.MinimumLoggingLevel")))
    .WriteTo.RollingFile(Configuration.GetValue<string>("AppSettings.RollingFilePath"))

"AppSettings": {
    "RollingFilePath": "..."
},

{
   "Logging": {
   "IncludeScopes": false,
   "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
      }
   }
}

var IncludeScopes = Configuration.GetValue<bool>("Logging:IncludeScopes", true);

基本上，我需要能够从启动构造函数中的appsettings.json访问值。大概是这样的：

public Startup(IHostingEnvironment env)
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
        .AddEnvironmentVariables();
    Configuration = builder.Build();

    Log.Logger = new LoggerConfiguration()
        .MinimumLevel.Debug()
        .WriteTo.RollingFile("C:/LogFiles/log-{Date}.txt")
        .CreateLogger();
}

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Is((LogEventLevel)Enum.Parse(typeof(LogEventLevel),
        Configuration.GetValue<string>("AppSettings.MinimumLoggingLevel")))
    .WriteTo.RollingFile(Configuration.GetValue<string>("AppSettings.RollingFilePath"))

"AppSettings": {
    "RollingFilePath": "..."
},

{
   "Logging": {
   "IncludeScopes": false,
   "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
      }
   }
}

var IncludeScopes = Configuration.GetValue<bool>("Logging:IncludeScopes", true);

Log.Logger=new LoggerConfiguration（）
.MinimumLevel.Is（（LogEventLevel）枚举解析（typeof（LogEventLevel），
Configuration.GetValue（“AppSettings.MinimumLoggingLevel”））
.WriteTo.RollingFile（Configuration.GetValue（“AppSettings.RollingFilePath”））

---

我在另一篇SO帖子中找到了

Configuration.GetValue

语法，但如果

AppSettings

部分如下所示，它总是返回

null

：

public Startup(IHostingEnvironment env)
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
        .AddEnvironmentVariables();
    Configuration = builder.Build();

    Log.Logger = new LoggerConfiguration()
        .MinimumLevel.Debug()
        .WriteTo.RollingFile("C:/LogFiles/log-{Date}.txt")
        .CreateLogger();
}

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Is((LogEventLevel)Enum.Parse(typeof(LogEventLevel),
        Configuration.GetValue<string>("AppSettings.MinimumLoggingLevel")))
    .WriteTo.RollingFile(Configuration.GetValue<string>("AppSettings.RollingFilePath"))

"AppSettings": {
    "RollingFilePath": "..."
},

{
   "Logging": {
   "IncludeScopes": false,
   "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
      }
   }
}

var IncludeScopes = Configuration.GetValue<bool>("Logging:IncludeScopes", true);

然后将

更改为

：

.WriteTo.RollingFile(Configuration.GetValue<string>("AppSettings:RollingFilePath"))

---

My appsettings.json如下所示：

public Startup(IHostingEnvironment env)
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
        .AddEnvironmentVariables();
    Configuration = builder.Build();

    Log.Logger = new LoggerConfiguration()
        .MinimumLevel.Debug()
        .WriteTo.RollingFile("C:/LogFiles/log-{Date}.txt")
        .CreateLogger();
}

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Is((LogEventLevel)Enum.Parse(typeof(LogEventLevel),
        Configuration.GetValue<string>("AppSettings.MinimumLoggingLevel")))
    .WriteTo.RollingFile(Configuration.GetValue<string>("AppSettings.RollingFilePath"))

"AppSettings": {
    "RollingFilePath": "..."
},

{
   "Logging": {
   "IncludeScopes": false,
   "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
      }
   }
}

var IncludeScopes = Configuration.GetValue<bool>("Logging:IncludeScopes", true);

要访问某个值，我可以使用如下内容：

public Startup(IHostingEnvironment env)
{
    var builder = new ConfigurationBuilder()
        .SetBasePath(env.ContentRootPath)
        .AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
        .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true)
        .AddEnvironmentVariables();
    Configuration = builder.Build();

    Log.Logger = new LoggerConfiguration()
        .MinimumLevel.Debug()
        .WriteTo.RollingFile("C:/LogFiles/log-{Date}.txt")
        .CreateLogger();
}

Log.Logger = new LoggerConfiguration()
    .MinimumLevel.Is((LogEventLevel)Enum.Parse(typeof(LogEventLevel),
        Configuration.GetValue<string>("AppSettings.MinimumLoggingLevel")))
    .WriteTo.RollingFile(Configuration.GetValue<string>("AppSettings.RollingFilePath"))

"AppSettings": {
    "RollingFilePath": "..."
},

{
   "Logging": {
   "IncludeScopes": false,
   "LogLevel": {
      "Default": "Debug",
      "System": "Information",
      "Microsoft": "Information"
      }
   }
}

var IncludeScopes = Configuration.GetValue<bool>("Logging:IncludeScopes", true);

var IncludeScopes=Configuration.GetValue（“记录：IncludeScopes”，true）；