如何从 .NET Core 中的 appsettings.json 读取部分值

Question

我正在使用 .NET Core 5.0。我在 appsettings.json 文件中有以下部分。

"Policies": [
        {
            "name": "ApproverPolicy",
            "description": "ApproverPolicy",
            "rules": [
                {
                    "name": "abc@gmail.com",
                    "description": "abc@gmail.com"
                },
                {
                    "name": "def@gmail.com",
                    "description": "def@gmail.com"
                }
            ]
        },
        {
            "name": "RegionPolicy",
            "description": "RegionPolicy",
            "rules": [
                {
                    "name": "East US",
                    "description": "East US"
                },
                {
                    "name": "North Europe",
                    "description": "North Europe"
                }
            ]
        }
    ]

我定义了以下 C# 类。

public class Policy : PolicyDefinition
{
    public IList<Rule> Rules { get; set; }
}
        
public class PolicyDefinition 
{
    public string Name { get; set; }
    public string Description { get; set; }
}
    
public class Rule
{
    public string Name { get; set; }
    public string Description { get; set; }
    public RuleStatus Status { get; set; }
    public DateTime UpdatedAt { get; set; }
    public string UpdatedBy { get; set; }
}
    
public enum RuleStatus
{
    Undefined = 0,
    Blocked = 1,
    Approved = 2,
    Rejected = 4,
    Unknown = 8
}

我正在使用以下代码从 appsettings.json 文件中读取策略部分。Name 和 Description 属性按预期填充，但“Rules”属性为 NULL。正确填充规则属性需要哪些更改？非常感激你的帮助。

_configuration.GetSection("Policies")
              .GetChildren()
              .ToList()
              .Select(x => new Policy
               {
                   Name = x.GetValue<string>("name"),
                   Description = x.GetValue<string>("description"),
                   Rules = x.GetValue<IList<Rule>>("rules")
                }).ToList();

以下代码适用于这种情况。感谢所有的帮助。

_configuration.GetSection("Policies").Get<List<Policy>>().ToList();

Answer 1

声明一个与您的 appsettings 结构相匹配的类会更容易。然后你可以在启动时设置它们并使用 IOptions 将它注入到类中。

用于启动

 var appSettingsSection = Configuration.GetSection("Policies");
 services.Configure<List<Policy>>(appSettingsSection);
 var appSettings = appSettingsSection.Get<List<Policy>>();

然后当你注射

public SomeClass(IOptions<List<Policy>> options){
     var policies = options.Value;
}