Question

我试图覆盖类常量变量，但我的方法不起作用。

以下代码：

// The following line of code should output "DATE: 9/9/2014"
// But it outputs: "DATE: 31/3/2015"
CustomDateChecker.checkUsedByDate();

在下面的课程中;如何覆盖变量USED_BY_YEAR，USED_BY_MONTH和USED_BY_DAY？

public class DateChecker
{
    public const uint                   USED_BY_YEAR            = 2015;
    public const uint                   USED_BY_MONTH           = 3;
    public const uint                   USED_BY_DAY             = 31;

    public static bool checkUsedByDate()
    {
        TaskDialog.MessageBox.Show(string.Format("DATE: {0}/{1}/{2}", USED_BY_DAY, USED_BY_MONTH, USED_BY_YEAR));
    }
}

public class CustomDateChecker : DateChecker
{
    // Override Date
    public const uint                   USED_BY_YEAR            = 2014;
    public const uint                   USED_BY_MONTH           = 9;
    public const uint                   USED_BY_DAY             = 9;
}

修改：在阅读建议后，我已将变量更改为static readonly而不是const。但不幸的是它同样的问题，日期并没有改变。使用static readonly可能的解决方案吗？

public class DateChecker
{
    public static readonly uint                   USED_BY_YEAR            = 2015;
    public static readonly uint                   USED_BY_MONTH           = 3;
    public static readonly uint                   USED_BY_DAY             = 31;

    public static bool checkUsedByDate()
    {
        TaskDialog.MessageBox.Show(string.Format("DATE: {0}/{1}/{2}", USED_BY_DAY, USED_BY_MONTH, USED_BY_YEAR));
    }
}

public class CustomDateChecker : DateChecker
{
    // Override Date
    public static new readonly uint                   USED_BY_YEAR            = 2014;
    public static new readonly uint                   USED_BY_MONTH           = 9;
    public static new readonly uint                   USED_BY_DAY             = 9;
}

Answer 1

public class DateChecker
    {
        public readonly uint USED_BY_YEAR = 2015;
        public readonly uint USED_BY_MONTH = 3;
        public readonly uint USED_BY_DAY = 31;

        public DateChecker()
        {

        }

        public DateChecker(uint d, uint m, uint y)
        {
            this.USED_BY_DAY = d;
            this.USED_BY_MONTH = m;
            this.USED_BY_YEAR = y;
        }

        public bool checkUsedByDate()
        {
            Console.WriteLine(string.Format("DATE: {0}/{1}/{2}", USED_BY_DAY, USED_BY_MONTH, USED_BY_YEAR));
            return false;
        }
    }

    public class CustomDateChecker : DateChecker
    {
        // Override Date
        public new const uint USED_BY_YEAR = 2014;
        public new const uint USED_BY_MONTH = 9;
        public new const uint USED_BY_DAY = 9;

        public CustomDateChecker()
            : base(USED_BY_DAY, USED_BY_MONTH, USED_BY_YEAR)
        {
        }


    }

    private static void Main(string[] args)
    {
        CustomDateChecker d = new CustomDateChecker();
        d.checkUsedByDate();
    }

Answer 2

您正在尝试覆盖字段或成员。覆盖是与方法/属性相关联的功能，而不是与类的字段或成员相关联。
这里的其他问题是你试图使用静态方法来获得不会成功的多态行为。静态方法与类相关联，而不是与类的实例相关联。因此，静态方法不能与虚拟/覆盖限定符一起使用。为此，应该使用实例方法/非静态方法或属性。

看看以下示例是否有帮助。

        public class DateChecker
        {
            public virtual uint USED_BY_YEAR { get; set; }
            public virtual uint USED_BY_MONTH { get; set; }
            public virtual uint USED_BY_DAY { get; set; }
            public DateChecker()
            {
                USED_BY_YEAR = 2015;
                USED_BY_MONTH = 3;
                USED_BY_DAY = 31;

            }
            public virtual void checkUsedByDate()
            {
                Console.Write(string.Format("DATE: {0}/{1}/{2}", USED_BY_DAY, USED_BY_MONTH, USED_BY_YEAR));
            }
        }

     public class CustomDateChecker : DateChecker
    {
        public override uint USED_BY_DAY
        {
            get
            {
                return 9;
            }
            set
            {
                base.USED_BY_DAY = value;
            }
        }

        public override uint USED_BY_MONTH
        {
            get
            {
                return 9;
            }
            set
            {
                base.USED_BY_MONTH = value;
            }
        }

        public override uint USED_BY_YEAR
        {
            get
            {
                return 2014;
            }
            set
            {
                base.USED_BY_YEAR = value;
            }
        }        
    }
    class Program
    {        
        static void Main(string[] args)
        {
            new CustomDateChecker().checkUsedByDate();
        }
    }

覆盖父常量变量

2 个答案: