c# - 有没有办法使用 F# 记录类型来提取 appsettings.json 配置？

Question

长话短说，当我使用类似 C# 的类时，我可以将 appsettings.json 提取到 Configuration 类型:

type Connection() =
    member val Host = Unchecked.defaultof<string> with get,set
    member val Port = Unchecked.defaultof<int> with get,set
    member val UserName = Unchecked.defaultof<string> with get,set
    member val Password = Unchecked.defaultof<string> with get,set

type Configuration() =
    member val RabbitMQ = Unchecked.defaultof<Connection> with get,set
    member val PostgreSQL = Unchecked.defaultof<Connection> with get,set

let fetchConfiguration =
        let builder = (new ConfigurationBuilder())
                          .SetBasePath(Directory.GetCurrentDirectory())
                          .AddJsonFile("appsettings.json", true, true)
                          .AddEnvironmentVariables(); 
        let configurationRoot = builder.Build();
        let configuration = new Configuration()
        configurationRoot.Bind(configuration)
        configuration

但是当使用 F# 记录类型时:

type Connection = {
    Host: string
    Port: int32
    Username: string
    Password: string
}

type Configuration = {
    RabbitMQ: Connection
    PostgreSQL: Connection
}

let fetchConfiguration =
        let builder = (new ConfigurationBuilder())
                          .SetBasePath(Directory.GetCurrentDirectory())
                          .AddJsonFile("appsettings.json", true, true)
                          .AddEnvironmentVariables(); 
        let configurationRoot = builder.Build();
        let configuration = {
            RabbitMQ = {
                Host = Unchecked.defaultof<string>
                Port = Unchecked.defaultof<int>
                Username = Unchecked.defaultof<string>
                Password = Unchecked.defaultof<string>
            }
            PostgreSQL = {
                Host = Unchecked.defaultof<string>
                Port = Unchecked.defaultof<int>
                Username = Unchecked.defaultof<string>
                Password = Unchecked.defaultof<string>
            }
        }
        configurationRoot.Bind(configuration)
        configuration

我最终得到的配置与我在调用“绑定(bind)”方法之前给出的值没有什么不同(即使我没有任何异常)，基本上就像什么都没发生一样。

注意:当我使用下面的默认值时，我有相同的行为:

let configuration = {
    RabbitMQ = Unchecked.defaultof<Connection>
    PostgreSQL = Unchecked.defaultof<Connection>
}

Answer 1

感谢上面的评论，解决方案只是设置 [<CLIMutable>] F# 记录类型的属性:

[<CLIMutable>]
type Connection = {
    Host: string
    Port: int32
    Username: string
    Password: string
}

[<CLIMutable>]
type Configuration = {
    RabbitMQ: Connection
    PostgreSQL: Connection
}

let fetchConfiguration =
        let builder = (new ConfigurationBuilder())
                          .SetBasePath(Directory.GetCurrentDirectory())
                          .AddJsonFile("appsettings.json", true, true)
                          .AddEnvironmentVariables(); 
        let configurationRoot = builder.Build();
        configurationRoot.Get<Configuration>()