C＃| Dictionary.Keys属性

此属性用于获取包含Dictionary中的键的集合。

句法：

public System.Collections.Generic.Dictionary.KeyCollection Keys { get; }

返回值：它返回一个包含Dictionary中键的集合。

下面是说明上述财产的使用的程序：

范例1：

// C# code to get the keys
// in the Dictionary
using System;
using System.Collections.Generic;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Create a new dictionary of
        // strings, with string keys.
        Dictionary myDict = 
           new Dictionary();
  
        // Adding key/value pairs in myDict
        myDict.Add("Australia", "Canberra");
        myDict.Add("Belgium", "Brussels");
        myDict.Add("Netherlands", "Amsterdam");
        myDict.Add("China", "Beijing");
        myDict.Add("Russia", "Moscow");
        myDict.Add("India", "New Delhi");
  
        // To get count of key/value pairs in myDict
        Console.WriteLine("Total key/value pairs"+
              " in myDict are : " + myDict.Count);
  
        // To get the keys alone, 
        // use the Keys property.
        Dictionary.KeyCollection keyColl = 
                                              myDict.Keys;
  
        // The elements of the KeyCollection
        // are strongly typed with the type 
        // that was specified for dictionary 
        // keys
        foreach(string s in keyColl)
        {
            Console.WriteLine("Key = {0}", s);
        }
    }
}

输出：

Total key/value pairs in myDict are : 6
Key = Australia
Key = Belgium
Key = Netherlands
Key = China
Key = Russia
Key = India

范例2：

// C# code to get the keys in the Dictionary
using System;
using System.Collections.Generic;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Create a new dictionary of
        // strings, with string keys.
        Dictionary myDict = 
          new Dictionary();
  
        // Adding key/value pairs in myDict
        myDict.Add(9, 8);
        myDict.Add(3, 4);
        myDict.Add(4, 7);
        myDict.Add(1, 7);
  
        // To get count of key/value pairs in myDict
        Console.WriteLine("Total key/value pairs "+
                "in myDict are : " + myDict.Count);
  
        // To get the keys alone, 
        // use the Keys property.
        Dictionary.KeyCollection keyColl = 
                                       myDict.Keys;
  
        // The elements of the KeyCollection
        // are strongly typed with the type 
        // that was specified for dictionary keys.
        foreach(int s in keyColl)
        {
            Console.WriteLine("Key = {0}", s);
        }
    }
}

输出：

Total key/value pairs in myDict are : 4
Key = 9
Key = 3
Key = 4
Key = 1

参考：

• https://docs.microsoft.com/zh-cn/dotnet/api/system.collections.generic.dictionary-2.keys?view=netframework-4.7.2