C＃|从OrderedDictionary中删除具有指定键的条目

OrderedDictionary.Remove(Object)方法用于从OrderedDictionary集合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。

例外情况：

• NotSupportedException：如果OrderedDictionary集合为只读。
• ArgumentNullException：如果键为null。

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 OrderedDictionary
using System;
using System.Collections;
using System.Collections.Specialized;
  
class GFG {
  
    // Driver method
    public static void Main()
    {
  
        // Creating a orderedDictionary named myDict
        OrderedDictionary myDict = new OrderedDictionary();
  
        // Adding key and value in myDict
        myDict.Add("key1", "value1");
        myDict.Add("key2", "value2");
        myDict.Add("key3", "value3");
        myDict.Add("key4", "value4");
        myDict.Add("key5", "value5");
  
        // Displaying the number of element initially
        Console.WriteLine("Number of elements are : " 
                                     + myDict.Count);
  
        // Displaying the elements in myDict
        foreach(DictionaryEntry de in myDict)
            Console.WriteLine(de.Key + " -- " + de.Value);
  
        // Removing the entry with the specified
        // key from the OrderedDictionary
        myDict.Remove("key2");
  
        // Displaying the number of element initially
        Console.WriteLine("Number of elements are : " 
                                     + myDict.Count);
  
        // Displaying the elements in myDict
        foreach(DictionaryEntry de in myDict)
            Console.WriteLine(de.Key + " -- " + de.Value);
    }
}

输出：

Number of elements are : 5
key1 -- value1
key2 -- value2
key3 -- value3
key4 -- value4
key5 -- value5
Number of elements are : 4
key1 -- value1
key3 -- value3
key4 -- value4
key5 -- value5

范例2：

// C# code to remove the entry
// with the specified key from
// the OrderedDictionary
using System;
using System.Collections;
using System.Collections.Specialized;
  
class GFG {
  
    // Driver method
    public static void Main()
    {
  
        // Creating a orderedDictionary named myDict
        OrderedDictionary myDict = new OrderedDictionary();
  
        // Adding key and value in myDict
        myDict.Add("A", "Apple");
        myDict.Add("B", "Banana");
        myDict.Add("C", "Cat");
        myDict.Add("D", "Dog");
  
        // Displaying the number of element initially
        Console.WriteLine("Number of elements are : " 
                                     + myDict.Count);
  
        // Displaying the elements in myDict
        foreach(DictionaryEntry de in myDict)
            Console.WriteLine(de.Key + " -- " + de.Value);
  
        // Removing the entry with the specified
        // key from the OrderedDictionary
        // This should raise "ArgumentNullException"
        // as the key is null
        myDict.Remove(null);
  
        // Displaying the number of element initially
        Console.WriteLine("Number of elements are : " 
                                     + myDict.Count);
  
        // Displaying the elements in myDict
        foreach(DictionaryEntry de in myDict)
            Console.WriteLine(de.Key + " -- " + de.Value);
    }
}

运行时错误：

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

笔记：

• 删除的条目之后的条目将向上移动以占据腾出的位置，并且被移动的条目的索引也会被更新。
• 如果OrderedDictionary集合不包含带有指定键的条目，则OrderedDictionary保持不变，并且不会引发任何异常。

参考：

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