配置GetSection返回对象部分的空值 [英] Configuration GetSection returns null value for object sections

问题描述

您好，我在 .NET Core应用中使用了 json 配置文件，但我不明白为什么我要为对象的子节得到null值:

Hello i am using a a json configuration file within a .NET Core App and i do not understand why i get the value null for subsections that are objects:

{
    "tt": {
        "aa":3,
        "x":4
    },
    "Url":333,
    "Config": {
        "Production": {
            "RedisAddress": {
                "Hostname": "redis0",
                "Port": 6379
            },
            "OwnAddress": {
                "Hostname": "0.0.0.0",
                "Port": 9300
            }
        },
        "Dev": {
            "RedisAddress": {
                "Hostname": "redis0",
                "Port": 6379
            },
            "OwnAddress": {
                "Hostname": "0.0.0.0",
                "Port": 9300
            },
            "Logger": "logger.txt"
        }
    }
}

当我尝试 GetSection("Config")或 GetSection("tt")时，我得到的值是 null .但是它会返回原始类型的值，例如我的 Url .

When i try GetSection("Config") or GetSection("tt") i get the value null.It however returns the value for primitive types like in my case Url.

有趣的是，如果我在 configuration.Providers [0] .Data 中查看，我会像图片中一样呈现所有内容:

What is funny is that if i peek inside the configuration.Providers[0].Data i have all the content present like in the picture:

为什么它为 object 类型返回null?

Why does it return null for object types?

代码

WebHostBuilder builder = new WebHostBuilder();
builder.UseStartup<Startup>();

string appPath = AppDomain.CurrentDomain.BaseDirectory;
string jsonPath = Path.Combine(Directory.GetParent(Directory.GetParent(appPath).FullName).FullName, "appsettings.json");

IConfiguration configuration = new ConfigurationBuilder()
    .SetBasePath(appPath)
    .AddJsonFile(jsonPath, optional: true, reloadOnChange: true)
    .Build();

var sect = configuration.GetSection("Config");//has value null
var sect2 = configuration.GetSection("tt");//has value null
var sect3 = configuration.GetSection("Url"); has value 333

推荐答案

两个答案( TanvirArjel 和

Both answers (TanvirArjel and Kirk Larkin) are correct. I am just going to clarify things for you and provide another way of getting the value form the configuration file.

要从 appsettings.json 中获取一个值，您需要将该值的路径(以冒号分隔的)传递给 configuration .

To get a value from appsettings.json you need to pass the path of the value (colon-separated) to the configuration.

有多种方法可以在不将节绑定到类的情况下获取值.例如:

There are different ways to get the value without binding the section to a class. E.g.:

var aaAsString = configuration["tt:aa"]; //will return the value as a string "3".
//To get the actual value type you need to cast them 
var aa1 = configuration.GetValue<int>("tt:aa"); //returns 3.
var aa2 = configuration.GetSection("tt").GetValue<int>("aa");
var aa3 = configuration.GetSection("tt").GetValue(typeof(int), "aa");

这篇关于配置GetSection返回对象部分的空值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！