Pair Class in C#

The KeyValuePair structure in C# allows you to store a pair of related values as a single unit. It is commonly used in collections like Dictionary and can be used in lists to store paired data such as name-value combinations or key-identifier pairs.

The KeyValuePair<TKey, TValue> is a generic structure that provides a way to store two related pieces of data together, where TKey represents the key type and TValue represents the value type.

Syntax

Following is the syntax for creating a KeyValuePair −

KeyValuePair<TKey, TValue> pair = new KeyValuePair<TKey, TValue>(key, value);

Following is the syntax for creating a list of KeyValuePair −

var list = new List<KeyValuePair<TKey, TValue>>();
list.Add(new KeyValuePair<TKey, TValue>(key, value));

Properties

The KeyValuePair structure provides two main properties −

• Key − Gets the key in the key/value pair.

• Value − Gets the value in the key/value pair.

Creating and Using KeyValuePair

Example

using System;
using System.Collections.Generic;

class Program {
   static void Main() {
      var myList = new List<KeyValuePair<string, int>>();
      
      // adding elements
      myList.Add(new KeyValuePair<string, int>("Laptop", 1));
      myList.Add(new KeyValuePair<string, int>("Desktop System", 2));
      myList.Add(new KeyValuePair<string, int>("Tablet", 3));
      myList.Add(new KeyValuePair<string, int>("Mobile", 4));
      myList.Add(new KeyValuePair<string, int>("E-Book Reader", 5));
      myList.Add(new KeyValuePair<string, int>("LED", 6));

      foreach (var val in myList) {
         Console.WriteLine(val);
      }
   }
}

The output of the above code is −

[Laptop, 1]
[Desktop System, 2]
[Tablet, 3]
[Mobile, 4]
[E-Book Reader, 5]
[LED, 6]

Accessing Key and Value Properties

Example

using System;
using System.Collections.Generic;

class Program {
   static void Main() {
      var products = new List<KeyValuePair<string, double>>();
      
      products.Add(new KeyValuePair<string, double>("Laptop", 999.99));
      products.Add(new KeyValuePair<string, double>("Mouse", 25.50));
      products.Add(new KeyValuePair<string, double>("Keyboard", 75.00));

      Console.WriteLine("Product Details:");
      foreach (var product in products) {
         Console.WriteLine($"Product: {product.Key}, Price: ${product.Value}");
      }
      
      // Accessing individual elements
      Console.WriteLine($"\nFirst product: {products[0].Key} costs ${products[0].Value}");
   }
}

The output of the above code is −

Product Details:
Product: Laptop, Price: $999.99
Product: Mouse, Price: $25.5
Product: Keyboard, Price: $75

First product: Laptop costs $999.99

Creating KeyValuePair with Different Data Types

Example

using System;
using System.Collections.Generic;

class Program {
   static void Main() {
      // Different data type combinations
      var studentGrades = new List<KeyValuePair<string, char>>();
      var settings = new List<KeyValuePair<string, bool>>();
      
      studentGrades.Add(new KeyValuePair<string, char>("John", 'A'));
      studentGrades.Add(new KeyValuePair<string, char>("Mary", 'B'));
      
      settings.Add(new KeyValuePair<string, bool>("DarkMode", true));
      settings.Add(new KeyValuePair<string, bool>("AutoSave", false));

      Console.WriteLine("Student Grades:");
      foreach (var grade in studentGrades) {
         Console.WriteLine($"{grade.Key}: {grade.Value}");
      }

      Console.WriteLine("\nSettings:");
      foreach (var setting in settings) {
         Console.WriteLine($"{setting.Key}: {setting.Value}");
      }
   }
}

The output of the above code is −

Student Grades:
John: A
Mary: B

Settings:
DarkMode: True
AutoSave: False

Conclusion

KeyValuePair in C# is a versatile structure for storing two related values as a single unit. It's particularly useful when you need to maintain associations between different data types and provides easy access to both key and value components through its properties.