KeyedCollection字符串不区分大小写

Question

我试着按照文档操作，但我不能让它工作。有一个包含密钥字符串的KeyedCollection。

如何在KeyedCollection中使字符串键不区分大小写？

可以只在ctor中传递StringComparer.OrdinalIgnoreCase。

private static WordDefKeyed wordDefKeyed = new WordDefKeyed(StringComparer.OrdinalIgnoreCase);   // this fails

public class WordDefKeyed : KeyedCollection<string, WordDef>
{
        // The parameterless constructor of the base class creates a 
        // KeyedCollection with an internal dictionary. For this code 
        // example, no other constructors are exposed.
        //
        public WordDefKeyed() : base() { }

        public WordDefKeyed(IEqualityComparer<string> comparer)
            : base(comparer)
        {
            // what do I do here???????
        }

        // This is the only method that absolutely must be overridden,
        // because without it the KeyedCollection cannot extract the
        // keys from the items. The input parameter type is the 
        // second generic type argument, in this case OrderItem, and 
        // the return value type is the first generic type argument,
        // in this case int.
        //
        protected override string GetKeyForItem(WordDef item)
        {
            // In this example, the key is the part number.
            return item.Word;
        }
}

private static Dictionary<string, int> stemDef = new Dictionary<string, int(StringComparer.OrdinalIgnoreCase);   // this works this is what I want for KeyedCollection

Answer 1

如果您希望默认情况下类型WordDefKeyed不区分大小写，那么默认的无参数构造函数应该向其传递一个IEqualityComparer实例，如下所示：

public WordDefKeyed() : base(StringComparer.OrdinalIgnoreCase) { }

StringComparer class具有一些常用的默认IEqualityComparer<T>实现，具体取决于您要存储的数据类型：

• StringComparer.Ordinal和StringComparer.CultureInvariantIgnoreCase -当您使用机器可读字符串时使用，而不是输入或显示到cultures.
• StringComparer.CurrentCulture和StringComparer.OrdinalIgnoreCase中的字符串-当您使用不会显示给UI但对区域性敏感且在cultures.
• StringComparer.CurrentCulture和StringComparer.CurrentCultureIgnoreCase中可能相同的字符串时使用-用于特定于当前区域性的字符串，例如在收集用户输入时。

如果需要当前区域性以外的区域性的StringComparer，则可以调用静态Create method为特定CultureInfo创建StringComparer。