扩展使用C＃泛型？ [英] Extending using C# generics?

问题描述

我想创建一个可扩展的嵌套结构，看起来我应该可以使用泛型来做到这一点，尽管我可能没有正确使用它们。

我想能够从GroupType和/或OptionType创建子类。问题是我不能对泛型类型执行 new 操作，即使我指定它们只能是某种基类型。

有没有办法做我想做的事情？

  public class AllInfo< GroupType，OptionType> 
其中GroupType：GroupBase< OptionType> 
其中OptionType：OptionBase 
 {
 public List< string>名称{set;得到; } 
 public List< GroupType>组{set;得到; } 
 $ b $ public AllInfo（）
 {
 DataSet ds = DatabaseRetreival（）; 
 this.Groups.add（new GroupType（ds [Name]，ds [Type]））; 
} 
 
} 
 
公共类GroupBase< OptionType> 
 where OptionType：OptionBase 
 {
 public string Name {set;得到; } 
 public string Type {set;得到; } 
 public List< OptionType>选项{set;得到; } 
 $ b $公共GroupBase（字符串名称，字符串类型）
 {
 this.Name = name; 
 this.Type = type; 
 
 DataSet ds = DatabaseRetreival（this.Type）; 
 this.Options.Add（new OptionType（ds [Name]））; 
} 
} 
 
 public class OptionBase 
 {
 public string Name {set;得到; } 
 
 public OptionBase（string name）
 {
 this.Name = name; 
 
 
 
 $ div $解析方案

你无法指定泛型类应该具有哪些构造函数。构造函数不是继承的，所以即使你指定的基类具有该构造函数，从它派生的类也不必具有该构造函数。

您可以要求的构造函数是无参数的构造函数：

 其中GroupType：GroupBase< OptionType> ;, new（）
  

因为只有让我们使用无参数构造函数，您还可以使用虚拟方法将数据放入对象中，例如：

  GroupType group = new GroupType（）; 
 group.Init（ds [Name]，ds [Type]）; 
 this.Groups.add（group）; 
  

I want to create an extendable nested structure and it seems like I should be able to do this using generics, though I may not be using them "properly".

I want to be able to create child classes from GroupType and/or OptionType. The problem is that I can't perform the new operation on the generic types even though I specified they could only be of a certain base type.

Is there any way to do what I'm trying to do?

public class AllInfo<GroupType, OptionType> 
    where GroupType: GroupBase<OptionType>
    where OptionType: OptionBase
{
    public List<string> Names { set; get; }
    public List<GroupType> Groups { set; get; }

    public AllInfo()
    {
        DataSet ds = DatabaseRetreival();
        this.Groups.add(new GroupType(ds["Name"], ds["Type"]));
    }

}

public class GroupBase<OptionType> 
    where OptionType: OptionBase
{
    public string Name { set; get; }
    public string Type { set; get; }
    public List<OptionType> Options { set; get; }

    public GroupBase(string name, string type)
    {
         this.Name = name;
         this.Type = type;

         DataSet ds = DatabaseRetreival(this.Type);
         this.Options.Add(new OptionType(ds["Name"]));
    }
}

public class OptionBase
{
    public string Name { set; get; }

    public OptionBase(string name)
    {
        this.Name = name;
    }
}

解决方案

You can't specify which constructors a generic class should have. The constructors are not inherited, so even if the base class that you specified has that constructor, a class that derives from it doesn't have to have that constructor.

The only constructor that you can require is the parameterless constructor:

where GroupType: GroupBase<OptionType>, new()

As that only let's you use the parameterless constructor, you would also use a virtual method for putting the data in the object, for example:

GroupType group = new GroupType();
group.Init(ds["Name"], ds["Type"]);
this.Groups.add(group);

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