当前位置: 首页>>代码示例 >>用法及示例精选 >>正文


C# Dictionary.Add()用法及代码示例


Dictionary.Add()方法用于向字典添加指定的键和值。

用法:

public void Add (TKey key, TValue value);

参数:


  • key: 这是要添加的元素的关键。
    value: 它是要添加的元素的值。对于引用类型,该值可以为null。

异常:

  • ArgumentNullException:如果键为null。
  • ArgumentException:如果词典中已经存在具有相同键的元素。

以下示例程序旨在说明Dictionary.Add()方法的使用:

示例1:

// C# code to add the specified key 
// and value into 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<string, string> myDict =  
           new Dictionary<string, string>(); 
  
        // 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); 
  
        // Displaying the key/value 
        // pairs in myDict 
        Console.WriteLine("The key/value pairs"+ 
                           " in myDict are : "); 
  
        foreach(KeyValuePair<string, string> kvp in myDict) 
        { 
            Console.WriteLine("Key = {0}, Value = {1}", 
                              kvp.Key, kvp.Value); 
        } 
    } 
}
输出:
Total key/value pairs in myDict are : 6
The key/value pairs in myDict are : 
Key = Australia, Value = Canberra
Key = Belgium, Value = Brussels
Key = Netherlands, Value = Amsterdam
Key = China, Value = Beijing
Key = Russia, Value = Moscow
Key = India, Value = New Delhi

示例2:

// C# code to add the specified  
// key and value into 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<string, string> myDict =  
          new Dictionary<string, string>(); 
  
        // 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"); 
  
        // The Add method throws an 
        // exception if the new key is 
        // already in the dictionary. 
        try { 
  
            myDict.Add("Russia", "Moscow"); 
        } 
  
        catch (ArgumentException) { 
  
            Console.WriteLine("An element with Key "+ 
                     "= \"Russia\" already exists."); 
        } 
    } 
}
输出:
An element with Key = "Russia" already exists.

注意:

  • 键不能为null,但如果TValue是引用类型,则值可以为null。
  • 如果Count小于容量,则此方法将执行O(1)操作。
  • 如果必须增加容量以容纳新元素,则此方法将成为O(n)操作,其中n为Count。

参考:



相关用法


注:本文由纯净天空筛选整理自rupesh_rao大神的英文原创作品 C# | Dictionary.Add() Method。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。