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C# | Remove entry with specified key from the StringDictionary
  • Last Updated : 01 Feb, 2019

StringDictionary.Remove(String) method is used to remove the entry with the specified key from the string dictionary.

Syntax:

public virtual void Remove (string key);

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

Exceptions:

  • ArgumentNullException: If the key is null.
  • NotSupportedException: If the StringDictionary is read-only.

Below programs illustrate the use of StringDictionary.Remove(String) method:



Example 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);
        }
    }
}

Output:

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

Example 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);
        }
    }
}

Runtime Error:

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

Note:

  • If the StringDictionary does not contain an element with the specified key, the StringDictionary remains unchanged. No exception is thrown.
  • The key is handled in a case-insensitive manner, i.e, it is translated to lowercase before it is used to find the entry to remove from the StringDictionary.
  • This method is an O(1) operation.

Reference:

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