C＃|从HybridDictionary中删除指定的键条目

HybridDictionary.Remove(Object)方法用于从HybridDictionary中删除具有指定键的条目。

句法：

public void Remove (object key);

在此， key是要删除的条目的键。

异常：如果键为null，则此方法将引发ArgumentNullException 。

下面给出了一些示例，以更好地理解实现：

范例1：

// C# code to remove the entry
// with the specified key from
// the HybridDictionary.
using System;
using System.Collections;
using System.Collections.Specialized;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Creating a HybridDictionary named myDict
        HybridDictionary myDict = new HybridDictionary();
  
        // Adding key/value pairs in myDict
        myDict.Add("A", "Apple");
        myDict.Add("B", "Banana");
        myDict.Add("C", "Cat");
        myDict.Add("D", "Dog");
        myDict.Add("E", "Elephant");
        myDict.Add("F", "Fish");
  
        // Displaying the number of key/value
        // pairs in HybridDictionary myDict
        Console.WriteLine("Number of 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(DictionaryEntry de in myDict)
        {
            Console.WriteLine(de.Key + " --> " + de.Value);
        }
  
        // Removing the entry with the
        // specified key from the HybridDictionary.
        myDict.Remove("C");
  
        // Displaying the number of key/value
        // pairs in HybridDictionary myDict
        Console.WriteLine("Number of 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(DictionaryEntry de in myDict)
        {
            Console.WriteLine(de.Key + " --> " + de.Value);
        }
    }
}

输出：

Number of key/value pairs in myDict are : 6
The key/value pairs in myDict are : 
A --> Apple
B --> Banana
C --> Cat
D --> Dog
E --> Elephant
F --> Fish
Number of key/value pairs in myDict are : 5
The key/value pairs in myDict are : 
A --> Apple
B --> Banana
D --> Dog
E --> Elephant
F --> Fish

范例2：

// C# code to remove the entry
// with the specified key from
// the HybridDictionary.
using System;
using System.Collections;
using System.Collections.Specialized;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Creating a HybridDictionary named myDict
        HybridDictionary myDict = new HybridDictionary();
  
        // Adding key/value pairs in myDict
        myDict.Add("I", "first");
        myDict.Add("II", "second");
        myDict.Add("III", "third");
        myDict.Add("IV", "fourth");
        myDict.Add("V", "fifth");
  
        // Displaying the number of key/value
        // pairs in HybridDictionary myDict
        Console.WriteLine("Number of 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(DictionaryEntry de in myDict)
        {
            Console.WriteLine(de.Key + " --> " + de.Value);
        }
  
        // Removing the entry with the
        // specified key from the HybridDictionary.
        // This should raise "ArgumentNullException"
        // as the key is "null"
        myDict.Remove(null);
  
        // Displaying the number of key/value
        // pairs in HybridDictionary myDict
        Console.WriteLine("Number of 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(DictionaryEntry de in myDict)
        {
            Console.WriteLine(de.Key + " --> " + de.Value);
        }
    }
}

运行时错误：

Unhandled Exception:
System.ArgumentNullException: Key cannot be null.
Parameter name: key

笔记：

• 如果HybridDictionary不包含带有指定键的元素，则HybridDictionary保持不变。没有异常被抛出。
• 如果该集合已经存储在Hashtable中，并且元素的数量低于ListDictionary的最佳大小，则该集合将保留在Hashtable中，以避免将元素从Hashtable复制回ListDictionary的开销。
• 此方法是O(1)操作。

参考：

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