C# | Gets or sets the value at the specified key in StringDictionary

StringDictionary.Item[String] Property is used to get or set the value associated with the specified key.

Syntax:

public virtual string this[string key] { get; set; }

Here, key is the Key of type System.String whose value is be to get or set.

Return Value: This property returns the value associated with the specified key. If the specified key is not found, Get returns null, and Set creates a new entry with the specified key.

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

Below programs illustrate the use of above-discussed property:

Example 1:

// C# code to get or set the value at 
// the specified key in StringDictionary 
using System; 
using System.Collections; 
using System.Collections.Specialized; 
  
class GFG { 
  
    // Driver code 
    public static void Main() 
    { 
  
        // Creating a StringDictionary named my1 
        StringDictionary my1 = new StringDictionary(); 
  
        // Adding key and value into the StringDictionary 
        my1.Add("1", "C"); 
        my1.Add("2", "C++"); 
        my1.Add("3", "Java"); 
        my1.Add("4", "Python"); 
        my1.Add("5", "C#"); 
  
        // Displaying the keys and 
        // values in StringDictionary 
        foreach(DictionaryEntry d in my1) 
        { 
            Console.WriteLine(d.Key + " " + d.Value); 
        } 
  
        Console.WriteLine("\nAfter Item[String] Property: \n"); 
  
        // setting the value at key 2 
        my1["2"] = "HTML"; 
  
        // Displaying the keys and 
        // values in StringDictionary 
        foreach(DictionaryEntry d1 in my1) 
        { 
            Console.WriteLine(d1.Key + " " + d1.Value); 
        } 
    } 
} 

Output:

3 Java
5 C#
4 Python
2 C++
1 C

After Item[String] Property: 

3 Java
4 Python
2 HTML
1 C
5 C#

Example 2:

// C# code to get or set the value at 
// the specified key in StringDictionary 
using System; 
using System.Collections; 
using System.Collections.Specialized; 
  
class GFG { 
  
    // Driver code 
    public static void Main() 
    { 
  
        // Creating a StringDictionary named my1 
        StringDictionary my1 = new StringDictionary(); 
  
        // Adding key and value into the StringDictionary 
        my1.Add("1", "HTML"); 
        my1.Add("2", "CSS"); 
        my1.Add("3", "PHP"); 
        my1.Add("4", "MongoDB"); 
        my1.Add("5", "AngularJS"); 
  
        // Displaying the keys and 
        // values in StringDictionary 
        foreach(DictionaryEntry d in my1) 
        { 
            Console.WriteLine(d.Key + " " + d.Value); 
        } 
  
        Console.WriteLine("\nAfter Item[String] Property: \n"); 
  
        // setting the value at Key 8 
        // here key 8 is not present 
        // so it will add a new key/value 
        // pair. see output 
        my1["8"] = "C#"; 
  
        // Displaying the keys and 
        // values in StringDictionary 
        foreach(DictionaryEntry d1 in my1) 
        { 
            Console.WriteLine(d1.Key + " " + d1.Value); 
        } 
    } 
} 

Output:

3 PHP
5 AngularJS
4 MongoDB
2 CSS
1 HTML

After Item[String] Property: 

3 PHP
4 MongoDB
2 CSS
1 HTML
8 C#
5 AngularJS

Reference:

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

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