C＃|在StringDictionary中获取键的集合

StringDictionary.Keys属性用于获取StringDictionary中的键的集合。

句法：

public virtual System.Collections.ICollection Keys { get; }

返回值：一个ICollection，它提供StringDictionary中的键。

下面给出了一些示例，以更好地理解实现：

范例1：

// C# code to get a collection
// of keys in the StringDictionary
using System;
using System.Collections;
using System.Collections.Specialized;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Creating a StringDictionary named myDict
        StringDictionary myDict = new StringDictionary();
  
        // Adding key and value into the StringDictionary
        myDict.Add("A", "Apple");
        myDict.Add("B", "Banana");
        myDict.Add("C", "Cat");
        myDict.Add("D", "Dog");
  
        // To copy the StringDictionary values to
        // a one-dimensional Array instance at
        // the specified index.
        String[] myKeys = new String[myDict.Count];
        myDict.Keys.CopyTo(myKeys, 0);
  
        // Getting a collection of keys
        // in the StringDictionary
        for (int i = 0; i < myDict.Count; i++) {
            Console.WriteLine(myKeys[i] + " " + myDict[myKeys[i]]);
        }
    }
}

输出：

d Dog
b Banana
c Cat
a Apple

范例2：

// C# code to get a collection
// of keys in the StringDictionary
using System;
using System.Collections;
using System.Collections.Specialized;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Creating a StringDictionary named myDict
        StringDictionary myDict = new StringDictionary();
  
        // Adding key and value into the StringDictionary
        myDict.Add("3", "prime & odd");
        myDict.Add("2", "prime & even");
        myDict.Add("4", "non-prime & even");
        myDict.Add("9", "non-prime & odd");
  
        // To copy the StringDictionary values to
        // a one-dimensional Array instance at
        // the specified index.
        String[] myKeys = new String[myDict.Count];
        myDict.Keys.CopyTo(myKeys, 0);
  
        // Getting a collection of keys
        // in the StringDictionary
        for (int i = 0; i < myDict.Count; i++) {
            Console.WriteLine(myKeys[i] + " " + myDict[myKeys[i]]);
        }
    }
}

输出：

2 prime & even
3 prime & odd
9 non-prime & odd
4 non-prime & even

笔记：

• ICollection中的键顺序未指定，但与Values方法返回的ICollection中的关联值的顺序相同。
• 返回的ICollection不是静态副本。而是，ICollection引用了原始StringDictionary中的键。因此，对StringDictionary的更改将继续反映在ICollection中。
• 检索此属性的值是O(1)操作。

参考：

• https://docs.microsoft.com/zh-cn/dotnet/api/system.collections.specialized.stringdictionary.keys?view=netframework-4.7.2