Get or set the value associated with the specified key in StringDictionary in C#

The StringDictionary class in C# provides an indexer that allows you to get or set values associated with specified keys. This indexer uses the key as a parameter and returns or assigns the corresponding value. The StringDictionary is case-insensitive and specifically designed for string keys and values.

Syntax

Following is the syntax for the StringDictionary indexer −

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

To get a value −

string value = stringDictionary[key];

To set a value −

stringDictionary[key] = value;

Parameters

• key − The string key whose associated value you want to get or set.

Return Value

Returns the string value associated with the specified key. If the key is not found, it returns null.

Getting Values from StringDictionary

You can retrieve values from a StringDictionary using the indexer with square bracket notation −

using System;
using System.Collections.Specialized;

public class Demo {
   public static void Main() {
      StringDictionary strDict = new StringDictionary();
      strDict.Add("A", "Books");
      strDict.Add("B", "Electronics");
      strDict.Add("C", "Appliances");
      strDict.Add("D", "Pet Supplies");
      strDict.Add("E", "Clothing");
      strDict.Add("F", "Footwear");
      
      Console.WriteLine("Value associated with key D = " + strDict["D"]);
      Console.WriteLine("Value associated with key F = " + strDict["F"]);
      Console.WriteLine("Value associated with key X = " + strDict["X"]);
   }
}

The output of the above code is −

Value associated with key D = Pet Supplies
Value associated with key F = Footwear
Value associated with key X = 

Setting Values in StringDictionary

You can also use the indexer to modify existing values or add new key-value pairs −

using System;
using System.Collections.Specialized;

public class Demo {
   public static void Main() {
      StringDictionary strDict = new StringDictionary();
      strDict.Add("A", "Books");
      strDict.Add("B", "Electronics");
      strDict.Add("C", "Appliances");
      strDict.Add("D", "Pet Supplies");
      strDict.Add("E", "Clothing");
      strDict.Add("F", "Footwear");
      
      Console.WriteLine("Original value for key F = " + strDict["F"]);
      
      // Update existing value
      strDict["F"] = "Sports Equipment";
      Console.WriteLine("Updated value for key F = " + strDict["F"]);
      
      // Add new key-value pair using indexer
      strDict["G"] = "Home Decor";
      Console.WriteLine("New value for key G = " + strDict["G"]);
   }
}

The output of the above code is −

Original value for key F = Footwear
Updated value for key F = Sports Equipment
New value for key G = Home Decor

Case-Insensitive Behavior

The StringDictionary treats keys in a case-insensitive manner. This means keys like "A" and "a" are considered the same −

using System;
using System.Collections.Specialized;

public class Demo {
   public static void Main() {
      StringDictionary strDict = new StringDictionary();
      strDict.Add("Product", "Laptop");
      
      Console.WriteLine("Value with 'Product' = " + strDict["Product"]);
      Console.WriteLine("Value with 'PRODUCT' = " + strDict["PRODUCT"]);
      Console.WriteLine("Value with 'product' = " + strDict["product"]);
      
      // Update using different case
      strDict["PRODUCT"] = "Desktop";
      Console.WriteLine("Updated value with 'Product' = " + strDict["Product"]);
   }
}

The output of the above code is −

Value with 'Product' = Laptop
Value with 'PRODUCT' = Laptop
Value with 'product' = Laptop
Updated value with 'Product' = Desktop

Conclusion

The StringDictionary indexer provides a convenient way to access and modify values using string keys. It supports both getting existing values and setting new or updated values, with case-insensitive key matching for enhanced usability.