C# | Remove all entries from the ListDictionary

ListDictionary.Clear method is used to remove the all entries from the ListDictionary.

Syntax:

public void Clear ();

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

Example 1:

// C# code to remove all entries
// from the ListDictionary
using System;
using System.Collections;
using System.Collections.Specialized;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a ListDictionary named myDict
        ListDictionary myDict = new ListDictionary();

        // Adding key/value pairs in myDict
        myDict.Add("Australia", "Canberra");
        myDict.Add("Belgium", "Brussels");
        myDict.Add("Netherlands", "Amsterdam");
        myDict.Add("China", "Beijing");
        myDict.Add("Russia", "Moscow");
        myDict.Add("India", "New Delhi");

        // To get count of key/value pairs in myDict
        Console.WriteLine("Total 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 all entries from the ListDictionary
        myDict.Clear();

        // To get count of key/value pairs in myDict
        Console.WriteLine("Total 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:

Total key/value pairs in myDict are : 6
The key/value pairs in myDict are : 
Australia Canberra
Belgium Brussels
Netherlands Amsterdam
China Beijing
Russia Moscow
India New Delhi
Total key/value pairs in myDict are : 0
The key/value pairs in myDict are :

Example 2:

// C# code to remove all entries
// from the ListDictionary
using System;
using System.Collections;
using System.Collections.Specialized;

class GFG {

    // Driver code
    public static void Main()
    {

        // Creating a ListDictionary named myDict
        ListDictionary myDict = new ListDictionary();

        // 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");

        // To get count of key/value pairs in myDict
        Console.WriteLine("Total 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 all entries from the ListDictionary
        myDict.Clear();

        // To get count of key/value pairs in myDict
        Console.WriteLine("Total 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:

Total key/value pairs in myDict are : 5
The key/value pairs in myDict are : 
I first
II second
III third
IV fourth
V fifth
Total key/value pairs in myDict are : 0
The key/value pairs in myDict are :

Note:

• Count is set to zero, and references to other objects from elements of the collection are also released.
• This method is an O(1) operation.

Reference:

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