C＃|从StringDictionary中删除具有指定键的条目

StringDictionary.Remove(String)方法用于从字符串字典中删除具有指定键的条目。

句法：

public virtual void Remove (string key);

在此， key是要删除的条目的键。

例外情况：

• ArgumentNullException：如果键为null。
• NotSupportedException：如果StringDictionary是只读的。

下面的程序说明了StringDictionary.Remove(String)方法的用法：

范例1：

// C# code to remove the entry
// with the specified key from
// the StringDictionary
using System;
using System.Collections;
using System.Collections.Specialized;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Creating a StringDictionary named myDict
        StringDictionary myDict = new StringDictionary();
  
        // Adding key and value into the StringDictionary
        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 keys and values in StringDictionary
        Console.WriteLine("The number of key/value pairs are : " + myDict.Count);
  
        foreach(DictionaryEntry dic in myDict)
        {
            Console.WriteLine(dic.Key + " " + dic.Value);
        }
  
        // Removing the entry with the specified
        // key from the StringDictionary
        myDict.Remove("D");
  
        // Displaying the keys and values in StringDictionary
        Console.WriteLine("The number of key/value pairs are : " + myDict.Count);
  
        foreach(DictionaryEntry dic in myDict)
        {
            Console.WriteLine(dic.Key + " " + dic.Value);
        }
    }
}

输出：

The number of key/value pairs are : 6
b Banana
c Cat
a Apple
f Fish
d Dog
e Elephant
The number of key/value pairs are : 5
b Banana
c Cat
a Apple
f Fish
e Elephant

范例2：

// C# code to remove the entry
// with the specified key from
// the StringDictionary
using System;
using System.Collections;
using System.Collections.Specialized;
  
class GFG {
  
    // Driver code
    public static void Main()
    {
  
        // Creating a StringDictionary named myDict
        StringDictionary myDict = new StringDictionary();
  
        // Adding key and value into the StringDictionary
        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 keys and values in StringDictionary
        Console.WriteLine("The number of key/value pairs are : " + myDict.Count);
  
        foreach(DictionaryEntry dic in myDict)
        {
            Console.WriteLine(dic.Key + " " + dic.Value);
        }
  
        // Removing the entry with the specified
        // key from the StringDictionary
        // This should raise "ArgumentNullException"
        // as the key is null
        myDict.Remove(null);
  
        // Displaying the keys and values in StringDictionary
        Console.WriteLine("The number of key/value pairs are : " + myDict.Count);
  
        foreach(DictionaryEntry dic in myDict)
        {
            Console.WriteLine(dic.Key + " " + dic.Value);
        }
    }
}

运行时错误：

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

笔记：

• 如果StringDictionary不包含带有指定键的元素，则StringDictionary保持不变。没有异常被抛出。
• 密钥以不区分大小写的方式处理，即，在用于查找要从StringDictionary中删除的条目之前将其转换为小写。
• 此方法是O(1)操作。

参考：

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