Csharp . NET JSON属性自定义所需逻辑

如果希望在Number为10时强制Text存在且不为空，并且需要纯Newtonsoft解决方案，则可以在参数化构造函数中执行此操作:

public class Foo
{
    [JsonConstructor]
    // Make public if you want to enforce the same requirements during regular construction
    protected Foo(int number, string text) 
    {
        if (number > 10 && text == null)
            throw new ArgumentException("missing text");
        this.Number = number;
        this.Text = text;
    }
    
    // Remove if you want to enforce the same requirements during regular construction
    public Foo() { }
    
    [JsonProperty(Required = Required.Always)]
    public int Number { get; set; }

    public string Text { get; set; }
}

请注意，构造函数参数的名称必须与相应的属性相同，忽略大小写的差异.

here.第一次见面

或者，如果出于某种原因不喜欢使用构造函数，可以在[OnDeserialized]回调中进行判断:

public class Foo
{
    [JsonProperty(Required = Required.Always)]
    public int Number { get; set; }

    public string Text { get; set; }
    
    [System.Runtime.Serialization.OnDeserialized]
    void OnDeserializedMethod(System.Runtime.Serialization.StreamingContext context)
    {
        if (Number > 10 && Text == null)
        {
            throw new JsonSerializationException("missing text");
        }
    }
}

here.第一次见面

请注意，两种解决方案都将null的值与Text等同于缺失值. 如果你想让{"Number":20, "Text":null}有效，你需要采用一个更复杂的解决方案，比如记住Text是否曾经被设置过，并在[OnDeserialized]回调中判断它:

public class Foo
{
    [JsonProperty(Required = Required.Always)]
    public int Number { get; set; }

    string text;
    bool textSpecified;
    public string Text { get => text; set { text = value; textSpecified = true; } }
    
    [System.Runtime.Serialization.OnDeserialized]
    void OnDeserializedMethod(System.Runtime.Serialization.StreamingContext context)
    {
        if (Number > 10 && !textSpecified)
        {
            throw new JsonSerializationException("missing text");
        }
    }
}

演示小提琴#3 here.