C＃|获取一个包含哈希表中的键的ICollection

Hashtable.Keys属性用于获取包含Hashtable中的键的ICollection。

句法：

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

返回值：该属性返回一个ICollection，其中包含哈希表中的键。

笔记：

• ICollection中的键顺序未指定。
• 检索此属性的值是O(1)操作。

下面的程序说明了上面讨论的属性的用法：

范例1：

// C# code to get an ICollection containing
// the keys in the Hashtable.
using System;
using System.Collections;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Creating a Hashtable
        Hashtable myTable = new Hashtable();
  
        // Adding elements in Hashtable
        myTable.Add("4", "Even");
        myTable.Add("9", "Odd");
        myTable.Add("5", "Odd and Prime");
        myTable.Add("2", "Even and Prime");
  
        // Get a collection of the keys.
        ICollection c = myTable.Keys;
  
        // Displaying the contents
        foreach(string str in c)
            Console.WriteLine(str + ": " + myTable[str]);
    }
}

输出：

5: Odd and Prime
9: Odd
2: Even and Prime
4: Even

范例2：

// C# code to get an ICollection containing
// the keys in the Hashtable.
using System;
using System.Collections;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Creating a Hashtable
        Hashtable myTable = new Hashtable();
  
        // Adding elements in Hashtable
        myTable.Add("India", "Country");
        myTable.Add("Chandigarh", "City");
        myTable.Add("Mars", "Planet");
        myTable.Add("China", "Country");
  
        // Get a collection of the keys.
        ICollection c = myTable.Keys;
  
        // Displaying the contents
        foreach(string str in c)
            Console.WriteLine(str + ": " + myTable[str]);
    }
}

输出：

Chandigarh: City
India: Country
China: Country
Mars: Planet

参考：

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