C# 实现 IEnumerable<T> 的问题
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Troubles implementing IEnumerable<T>
提问by BlackBear
I'm trying to write my own (simple) implementation of List. This is what I did so far:
我正在尝试编写自己的（简单的）List 实现。这是我到目前为止所做的：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace provaIEnum
{
class MyList<T> : IEnumerable<T>
{
private T[] _array;
public int Count { get; private set; }
public MyList() { /* ... */ }
public void Add(T element) { /* ... */ }
// ...
public IEnumerator<T> GetEnumerator()
{
for (int i = 0; i < Count; i++)
yield return _array[i];
}
}
I'm getting an error about GetEnumerator though:
我收到了一个关于 GetEnumerator 的错误：
'provaIEnum.Lista' does not implement interface member 'System.Collections.IEnumerable.GetEnumerator()'. 'provaIEnum.Lista.GetEnumerator()' cannot implement 'System.Collections.IEnumerable.GetEnumerator()' because it does not have the matching return type of 'System.Collections.IEnumerator'.
'provaIEnum.Lista' 没有实现接口成员 'System.Collections.IEnumerable.GetEnumerator()'。“provaIEnum.Lista.GetEnumerator()”无法实现“System.Collections.IEnumerable.GetEnumerator()”，因为它没有“System.Collections.IEnumerator”的匹配返回类型。
I'm not sure if I understand what VS's trying to tell me and I have no idea how to fix it.
我不确定我是否理解 VS 试图告诉我的内容，我不知道如何解决它。
Thanks for your time
谢谢你的时间
采纳答案by Darin Dimitrov
Since IEnumerable<T>implements IEnumerableyou need to implement this interface as well in your class which has the non-generic version of the GetEnumeratormethod. To avoid conflicts you could implement it explicitly:
由于IEnumerable<T>实现，IEnumerable您还需要在具有GetEnumerator方法的非通用版本的类中实现此接口。为避免冲突，您可以明确实现它：
IEnumerator IEnumerable.GetEnumerator()
{
// call the generic version of the method
return this.GetEnumerator();
}
public IEnumerator<T> GetEnumerator()
{
for (int i = 0; i < Count; i++)
yield return _array[i];
}
回答by Rich O'Kelly
You'll need to implement the non-generic GetEnumerator method as well:
您还需要实现非通用的 GetEnumerator 方法：
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
Since the IEnumerable<T>interface extends IEnumerable, you have to implement the methods declared on both.
由于IEnumerable<T>接口 extends IEnumerable，您必须实现在两者上声明的方法。
回答by Eric Lippert
Read the error message more carefully; it is telling you exactly what you must do. You did not implement System.Collections.IEnumerable.GetEnumerator.
更仔细地阅读错误信息；它准确地告诉您必须做什么。你没有实施System.Collections.IEnumerable.GetEnumerator。
When you implement the genericIEnumerable<T>you have to also implement System.Collections.IEnumerable's GetEnumerator.
当您实现泛型时，IEnumerable<T>您还必须实现System.Collections.IEnumerable的 GetEnumerator。
The standard way to do so is:
这样做的标准方法是：
public IEnumerator<T> GetEnumerator () { whatever }
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return this.GetEnumerator();
}
回答by Chris Shain
Add the following method:
添加以下方法：
IEnumerator IEnumerable.GetEnumerator()
{
return this.GetEnumerator();
}
回答by Ilya Kogan
There are two overloads of GetEnumerator()that you must implement. One comes from IEnumerable<T>and returns IEnumerator<T>. The other comes from IEnumerable and returns IEnumerator. The override should look like this:
GetEnumerator()您必须实现两个重载。一个来自IEnumerable<T>并返回IEnumerator<T>。另一个来自 IEnumerable 并返回IEnumerator。覆盖应如下所示：
IEnumerator IEnumerable.GetEnumerator()
IEnumerator IEnumerable.GetEnumerator()
This is because IEnumerable<T>implements IEnumerable.
这是因为IEnumerable<T>实现IEnumerable.
回答by Michael Hornfeck
Since your class, MyList<T>inherits IEnumerable<out T>which in turn inherits the non-generic IEnumerable, you have two methods you need to implement:
由于类，MyList<T>继承IEnumerable<out T>这反过来又继承了非一般的IEnumerable，你有两个方法需要实现：
IEnumerator<T> IEnumerable<T>.GetEnumerator()
{
throw new NotImplementedException();
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
throw new NotImplementedException();
}
An easy way to do this is when you declare your class:
一个简单的方法是当你声明你的类时：
class MyList<T> : IEnumerable<T>
Right click the IEnumerable<T>text and select Implement Interface > Implement Interface Explictlyfrom the context menu.
右键单击IEnumerable<T>文本并从上下文菜单中选择“实现接口”>“显式实现接口”。
回答by RotatingWheel
I got similar problem,though I implemented also IEnumerable and IEnumerable. I was using custom type (Person class) than generic type T. For me the reason was, namespace was not included in the top of file.
我遇到了类似的问题，虽然我也实现了 IEnumerable 和 IEnumerable。我使用的是自定义类型（Person 类）而不是通用类型 T。对我来说，原因是命名空间未包含在文件顶部。
using System.Collections;
After adding the namespace it was fine for me.
添加命名空间后，对我来说很好。
