C# | Removing the specified key entry from HybridDictionary

HybridDictionary.Remove(Object) method is used to remove the entry with the specified key from the HybridDictionary.

Syntax:

public void Remove (object key);

Here, key is the key of the entry to remove.

Exception: This method throws ArgumentNullException if the key is null.

Below given are some examples to understand the implementation in a better way :

Example 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); 
        } 
    } 
} 

Output:

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

Example 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); 
        } 
    } 
} 

Runtime Error:

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

Note:

If the HybridDictionary does not contain an element with the specified key, the HybridDictionary remains unchanged. No exception is thrown.
If the collection is already stored in a Hashtable and the number of elements falls below the optimal size for a ListDictionary, the collection remains in the Hashtable to avoid the overhead of copying elements from the Hashtable back to a ListDictionary.
This method is an O(1) operation.

Reference:

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

My Personal Notes

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