C＃|从OrderedDictionary中删除指定索引处的条目

OrderedDictionary.RemoveAt(Int32)方法用于从OrderedDictionary集合中删除指定索引处的条目。

句法：

public void RemoveAt (int index);

在这里， index是要删除的条目的从零开始的索引。

例外情况：

• NotSupportedException：如果OrderedDictionary集合为只读。
• ArgumentOutOfRangeException：如果索引小于零或索引等于或大于Count。

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 at
// the specified index 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 at the specified
        // index from the OrderedDictionary
        myDict.RemoveAt(3);
  
        // 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
key2 -- value2
key3 -- value3
key5 -- value5

范例2：

// C# code to remove the entry at
// the specified index 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 at the specified
        // index from the OrderedDictionary
        // This should raise "ArgumentOutOfRangeException"
        // as index is less than 0
        myDict.RemoveAt(-2);
  
        // 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.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: index

注意：删除的条目之后的条目将向上移动以占据腾出的位置，并且移动的条目的索引也会被更新。

参考：

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