Question

我正在尝试实现一个相对简单的类层次结构。但是，从学校开始，我的一些知识似乎就丢失了。问题是子类的属性在检索时会丢失。

层次结构如下：

具有关于子类的一般属性的抽象类
具有特定属性的子类。继承自抽象类
子类的集合

集合

public class ActiveFilters
{
    public List<ActiveFilter> Filters { get; set; }
    enum FilterTypes 
    { 
        DateRange = 1,
        CheckBox = 2,
        TextBox = 3,
        RadioButtons = 4
    };

    public ActiveFilters()
    {
        Filters = new List<ActiveFilter>();

        //Required filters on start
        Filters.Add(
            new FilterDateRange(
                "/statistikstart.aspx",
                (int)FilterTypes.DateRange,
                "paymentDate",
                new DateTime(1800, 1, 1),
                DateTime.Now.AddDays(7)
            )
        );
        Filters.Add(
            new FilterDateRange(
                "/statistikgiro.aspx",
                (int)FilterTypes.DateRange,
                "paymentDate",
                new DateTime(1800, 1, 1),
                DateTime.Now
            )
        );
    }

    public ActiveFilter GetActiveFilter(string source, string name)
    {
        try
        {
            return Filters.FirstOrDefault(x => x.Source == source && x.Name == name) as ActiveFilter;
        }
        catch
        {
            //Filter not in collection
            return null;
        }
    }
}

抽象类

public abstract class ActiveFilter
{
    public string Source { get; set; }
    public int Type { get; set; }
    public string Name { get; set; }
}

子类

public class FilterDateRange : ActiveFilter
{
    public DateTime FromDate { get; set; }
    public DateTime ToDate { get; set; }

    public FilterDateRange(string source, int type, string name, DateTime fromDate, DateTime toDate)
    {
        base.Source = source;
        base.Type = type;
        base.Name = name;
        this.FromDate = FromDate;
        this.ToDate = ToDate;
    }
}

当我尝试从集合构造函数中检索一个创建的过滤器时，子类中没有保存日期。保存的唯一信息是抽象类的属性：

FilterDateRange test = ((FilterDateRange)((ActiveFilters)Session["activeFilters"]).GetActiveFilter("/statistikstart.aspx", "paymentDate"));

问题是我从GetActiveFilter（）而不是子类返回ActiveFilter吗？如果是这样，当过滤器可以是不同的子类时，如何重写GetActiveFilter（）以返回过滤器？

Answer 1

你有一些拼写错误：

public FilterDateRange(string source, int type, string name, DateTime fromDate, DateTime toDate)
{
    base.Source = source;
    base.Type = type;
    base.Name = name;
    this.FromDate = FromDate; // set FromDate to FromDate (the property) 
    this.ToDate = ToDate;
}

应该是

public FilterDateRange(string source, int type, string name, DateTime fromDate, DateTime toDate)
{
    base.Source = source;
    base.Type = type;
    base.Name = name;
    this.FromDate = fromDate; // set FromDate to fromDate (the parameter)
    this.ToDate = toDate;
}

在继承类的集合中丢失子类的属性

1 个答案: