如何通過 System.Text.Json 從文件加載值並將它們存儲為只讀？

Question

我想通過 System.Text.Json 從 JSON 文件加載設置。 這些設置在加載后都應該是只讀的。

到目前為止我的代碼：

string jsonString = File.ReadAllText(filename);
Settings s = JsonSerializer.Deserialize<Settings>(jsonString);

和設置類：

public class Settings
{
    public decimal A { get; set; }
    public int B { get; set; }
    public double C { get; set; }
    public double D { get; set; }
}

問題：值是可編輯的並使用private set; 不起作用，因為 JsonSerializer 需要能夠訪問 setter。

Answer 1

為序列化程序創建一個帶有公共set的基類，然后在不允許對其進行變異的派生類中覆蓋它們。

---

我建議您更改設計並創建一個具有所有可變屬性的基類，這將成為任何反序列化操作的目標（因為可變屬性與反序列化配合得很好）。 然后消費者將通過從該基類中隱蔽/復制/反射它來獲取不可變實例。

var bse = JsonConvert.DeserializeObject<MutablePropertyStore>("{ 'PropertyB' : true }");
Console.WriteLine("Base:    " +  bse.ToString());   

var derived = new ImmutablePropertyStore(bse);              
Console.WriteLine("Derived: " + derived.ToString());    

結果

Base:    Property A is 'False' and Property B is 'True'.
Derived: Property A is 'False' and Property B is 'True'.

---

示例.Net Fiddle

代碼

public sealed class ImmutablePropertyStore : MutablePropertyStore
{
    public new bool PropertyA { get; private set; }
    public new bool PropertyB { get; private set; }

    public ImmutablePropertyStore() { }

    public ImmutablePropertyStore(MutablePropertyStore ms)
    {
        PropertyA = ms.PropertyA;
        PropertyB = ms.PropertyB;
    }

    public ImmutablePropertyStore(bool propertyA = true, bool propertyB = false)
    {
        PropertyA = propertyA;
        PropertyB = propertyB;
    }

    public override string ToString() 
        => $"Property A is '{PropertyA}' and Property B is '{PropertyB}'."; 
}

public class MutablePropertyStore
{
    public virtual bool PropertyA { get; set;}
    public virtual bool PropertyB { get; set;}

    // Set all defaults here
    public MutablePropertyStore() {  }

    public override string ToString() 
        => $"Property A is '{PropertyA}' and Property B is '{PropertyB}'.";      

}