C# |从混合字典中删除指定的关键字条目

原文:https://www . geesforgeks . org/c-sharp-从混合字典中删除指定的关键字条目/

杂交词典。移除(对象)方法用于从混合字典中移除具有指定关键字的条目。

语法:

public void Remove (object key);

在这里， 键 是要移除的条目的键。

异常:此方法抛出ArgumentNullException如果关键是 空 。

下面给出了一些例子，以便更好地理解实现:

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

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:

未处理异常: 系统。ArgumentNullException:键不能为空。 参数名称:键

注:

  • 如果混合字典不包含具有指定键的元素，则混合字典保持不变。不会引发异常。
  • 如果集合已经存储在哈希表中，并且元素数量低于列表字典的最佳大小，则集合将保留在哈希表中，以避免将元素从哈希表复制回列表字典的开销。
  • 这个方法是一个 O(1) 运算。

参考:

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