转换StringCollection列出＆LT;字符串＆GT; [英] Convert StringCollection to List<String>

问题描述

通常情况下，我会选择名单，其中，字符串＆GT; [或者，在VB中，列表（串） ]在 StringCollection 尽可能：又见的 <一个href="http://stackoverflow.com/questions/669106/best-string-container-stringcollection-collectionstring-liststring-arraylist">Best字符串集装箱 的。

Normally, I'd choose List<String> [or, in VB, List(Of String)] over StringCollection whenever possible: see also Best string container.

不过，因为它似乎，仿制药 - 因此，名单，其中，字符串＆GT; - 显然不是在VS 2008的设置，设计支持。所以，如果我想用在我的用户设置字符串列表，我不得不求助于使用 StringCollection 那里。

However, as it seems, generics — and hence, List<String> — are apparently not supported in VS 2008's settings designer. Therefore, if I want to use a list of strings in my user settings, I have to resort to using a StringCollection there.

现在，因为我不希望看到 StringCollection 在我的code，我需要将其转换为名单，其中，字符串＆GT; 。如何做到这一点有效？或者，甚至更好，我是错误的，有一种方法使用名单，其中，字符串＆GT; 的设置设计师

Now as I don't want to see StringCollection throughout my code, I need to convert it to List<String>. How do I do this efficiently? Or, even better, am I mistaken and there is a way to use List<String> in settings designer?

编辑：我必须使用.NET 2.0 的

推荐答案

如果您的有无的使用.NET 2.0，我会想象cleanliest选项是创建一个包装 StringCollection 实现的IEnumerable＆LT;字符串＆GT; 和的IEnumerator＆LT;字符串＆GT; 的 StringCollection StringEnumerator 分别为C>和。 （注意的：根据元数据， StringEnumerator 不执行的IEnumerator ）。示例如下。然而，在一天结束的时候，有人在什么地方是打算做一个的foreach（）在 StringCollection ，所以一的可以的认为，一个简单的的foreach（字符串stringCollection项目），并增加了名单，其中，串＆GT; 就足够了;我怀疑这会不会是performat足以满足您的需求。

If you have to use .NET 2.0, I would imagine the cleanliest option would be to create a wrapper for StringCollection that implements IEnumerable<string> and IEnumerator<string> for StringCollection and StringEnumerator respectively. (note: according to metadata, StringEnumerator does not implement IEnumerator). Sample below. However, at the end of the day, someone, somewhere is going to be doing a foreach() over the StringCollection, so one could argue that a simple foreach(string item in stringCollection) and adding to the List<string> would suffice; I doubt this wouldn't be performat enough for your needs.

您也可以实施的IList＆LT;字符串＆GT; 使用这种方式为好，以节省您复制标的字符串，但是你将支付具有包装的处罚类型的委托调用（堆栈上的一个方法调用！）。我建议你​​无论如何对待你的系统内的事情，术语接口 IEnumberable＆LT;字符串＆GT; ，的IList＆LT;字符串＆GT; 而不是具体的名单等，它会引导你失望的路径，以更大的灵活性。

You could also implement IList<string> using this approach as well, to save you duplicating the underlying strings, but you'll pay a penalty of having the "wrapper" type delegate calls (one more method call on the stack!). I would suggest you treat things in-terms of interfaces within your system anyway IEnumberable<string>, IList<string> etc, instead of the concrete List, it will guide you down a path to greater flexibility.

    static void Main(string[] args)
    {
        StringCollection stringCollection = new StringCollection();
        stringCollection.AddRange(new string[] { "hello", "world" });

        // Wrap!
        List<string> listOfStrings = new List<string>(new StringCollectionEnumerable(stringCollection));

        Debug.Assert(listOfStrings.Count == stringCollection.Count);
        Debug.Assert(listOfStrings[0] == stringCollection[0]); 

    }

    private class StringCollectionEnumerable : IEnumerable<string>
    {
        private StringCollection underlyingCollection; 

        public StringCollectionEnumerable(StringCollection underlyingCollection)
        {
            this.underlyingCollection = underlyingCollection; 
        }

        public IEnumerator<string> GetEnumerator()
        {
            return new StringEnumeratorWrapper(underlyingCollection.GetEnumerator()); 
        }

        System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
        {
            return this.GetEnumerator(); 
        }
    }

    private class StringEnumeratorWrapper : IEnumerator<string>
    {
        private StringEnumerator underlyingEnumerator; 

        public StringEnumeratorWrapper(StringEnumerator underlyingEnumerator)
        {
            this.underlyingEnumerator = underlyingEnumerator;
        }

        public string Current
        {
            get
            {
                return this.underlyingEnumerator.Current; 
            }
        }

        public void Dispose()
        {
            // No-op 
        }

        object System.Collections.IEnumerator.Current
        {
            get
            {
                return this.underlyingEnumerator.Current;
            }
        }

        public bool MoveNext()
        {
            return this.underlyingEnumerator.MoveNext(); 
        }

        public void Reset()
        {
            this.underlyingEnumerator.Reset(); 
        }
    }

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