在C＃类中实现不同的索引器 [英] Implementation of different indexers within C# class
问题描述
我想在我的类中添加不同的索引器实现：
I'd like to add different indexer implementations in my class :
SpecificCollection
public class SpecificCollection<T> : ISpecificCollection <T>
{
public int this[int index]
{
get
{
throw new NotImplementedException();
}
set
{
throw new NotImplementedException();
}
}
public object this[int index]
{
get
{
throw new NotImplementedException();
}
set
{
throw new NotImplementedException();
}
}
public string this[int index]
{
get
{
throw new NotImplementedException();
}
set
{
throw new NotImplementedException();
}
}
public event void OnAddElement;
public event void OnRemoveElement;
public void AddNewElement(T element)
{
throw new NotImplementedException();
}
public void DeleteElement(int index)
{
throw new NotImplementedException();
}
public int Count
{
get
{
throw new NotImplementedException();
}
set
{
throw new NotImplementedException();
}
}
}
StudentSpecificCollection
StudentSpecificCollection
public class StudentSpecificCollection : SpecificCollection<Student>
{
private string[] arrName;
private int[] arrAge;
private object[] arrStudent ;
public int ISpecificCollectionIndexers<Student>.this[int index]
{
get
{
return arrAge[index];
}
set
{
arrAge[index] = value;
}
}
object ISpecificCollectionIndexers<Student>.this[int index]
{
get
{
return arrStudent[index];
}
set
{
arrStudent[index] = value;
}
}
string ISpecificCollectionIndexers<Student>.this[int index]
{
get
{
return arrName[index];
}
set
{
arrName[index] = value;
}
}
public event void OnAddElement;
public event void OnRemoveElement;
public void AddNewElement(Student element)
{
object objStudent = arrStudent.Where(x => x != null).LastOrDefault();
int index = (objStudent == null) ? 0 : Array.IndexOf(arrStudent, objStudent);
arrName[index] = element.Name ;
arrAge[index] = element.Age;
arrStudent[index] = element;
}
public void DeleteElement(int index)
{
if (index > Count - 1) return;
arrName[index] = null;
arrAge[index] = -1;
arrStudent[index] = null;
}
public int Count
{
get
{
return arrName.Where(x=>x !=null).Count();
}
set
{
}
}
public StudentSpecificCollection()
{
arrName = new string[100];
arrAge = new int[100];
arrStudent = new object[100];
}
}
所以我需要知道： / p>
So I need to know :
- 如何使用不同的索引器实现？
推荐答案
使用接口的显式实现，可以执行以下操作：
Using explicit implementation of interfaces, you can do something like:
public interface IMyClass
{
object this[int index]
{
get; set;
}
}
public class MyClass : IMyClass
{
public string this[int index]
{
get
{
return "";
}
set
{
}
}
object IMyClass.this[int index]
{
get
{
return "";
}
set
{
}
}
}
因此实现具有相同签名的两个不同的枚举器（其中signature =类型/输入参数的数量）。注意，你可以有多个接口，每个接口有一个不同的返回类型的索引器，所以给定x接口和一个类，你可以有x + 1个不同的索引器具有相同的签名。
so implement two different enumerators with the same signature (where signature = type/number of input parameters). Note that you can have multiple interfaces, each one with an indexer with a different return type, so given x interfaces and one class, you can have x + 1 distinct indexers with the same signature.
现在...如果 Student 是一个真实类而不是对象使用隐式转换做一些技巧（你不能使用/对对象类进行隐式转换）：
Now... If Student was a "real" class instead of an object, you could do some tricks with implicit casts (you can't do implicit casts with/against the object class):
public class StudentSpecificCollection
{
private string[] arrName;
private int[] arrAge;
private object[] arrStudent;
public MyObject this[int index]
{
get
{
return new MyObject(this, index);
}
set
{
if (value.Type.HasFlag(MyObject.MyObjectType.Name))
{
arrName[index] = value;
}
if (value.Type.HasFlag(MyObject.MyObjectType.Age))
{
arrAge[index] = value;
}
if (value.Type.HasFlag(MyObject.MyObjectType.Student))
{
arrStudent[index] = value;
}
}
}
public class MyObject
{
[Flags]
public enum MyObjectType
{
Name = 1,
Age = 2,
Student = 4
}
public readonly MyObjectType Type;
public readonly string Name;
public readonly int Age;
public readonly object Student;
protected MyObject(string name)
{
Type = MyObjectType.Name;
Name = name;
}
protected MyObject(int age)
{
Type = MyObjectType.Age;
Age = age;
}
protected MyObject(object student)
{
Type = MyObjectType.Student;
Student = student;
}
public MyObject(StudentSpecificCollection obj, int ix)
{
Name = obj.arrName[ix];
Age = obj.arrAge[ix];
Student = obj.arrStudent[ix];
}
public static implicit operator string(MyObject obj)
{
if (!obj.Type.HasFlag(MyObjectType.Name))
{
throw new Exception();
}
return obj.Name;
}
public static implicit operator int(MyObject obj)
{
if (!obj.Type.HasFlag(MyObjectType.Age))
{
throw new Exception();
}
return obj.Age;
}
//public static implicit operator object(MyObject obj)
//{
// if (!obj.Type.HasFlag(MyObjectType.Student))
// {
// throw new Exception();
// }
// return obj.Student;
//}
public static implicit operator MyObject(string name)
{
return new MyObject(name);
}
public static implicit operator MyObject(int age)
{
return new MyObject(age);
}
//public static implicit operator MyObject(object student)
//{
// return new MyObject(student);
//}
}
}
a MyObject 类，然后可以隐式转换为 int / string ）
(the indexer returns a MyObject class that then can be implicitly casted to int/string)
然后使用
var obj = new StudentSpecificCollection();
// Load some students here
obj[0] = "Foo";
obj[0] = 25;
string name = obj[0];
int age = obj[0];
请注意，我不要认为这是一个好主意。但您要求。
Note that I don't think this is a good idea. But you asked for it.
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