---
title: "C# Guides: Modularity, Encapsulation, Lambdas, Interoperability, and Asynchronous Programming"
---

# A Guide to Modularity, Encapsulation, Lambdas, Interoperability, and Asynchronous Programming

[TOC]

---
## Modularity
Modularity is a software design principle that promotes breaking a large, complex system into smaller, self-contained modules that can be developed, tested, and maintained independently.

Here is an example in C# code:

using System;

namespace Module1
{
    public class Module1Class
    {
        public void Method1()
        {
            Console.WriteLine("Method from Module1");
        }
    }
}

namespace Module2
{
    public class Module2Class
    {
        public void Method2()
        {
            Console.WriteLine("Method from Module2");
        }
    }
}

class Program
{
    static void Main()
    {
        var module1 = new Module1.Module1Class();
        var module2 = new Module2.Module2Class();

        module1.Method1();
        module2.Method2();
    }
}

In this example, we have two namespaces (Module1 and Module2) representing different modules. Each module contains its own classes and methods, making the code modular and maintainable.

---

## Encapsulation
Encapsulation is one of the fundamental principles of object-oriented programming (OOP), which involves bundling the data (attributes) and the methods (functions) that operate on the data into a single unit called a class. Access to the data is controlled through public, private, and protected access modifiers.

Here is an example in C# code:

class Employee
{
    private string name;
    private double salary;

    public Employee(string name, double salary)
    {
        this.name = name;
        this.salary = salary;
    }

    public void SetSalary(double newSalary)
    {
        if (newSalary > 0)
        {
            salary = newSalary;
        }
    }

    public double GetSalary()
    {
        return salary;
    }

    public string GetName()
    {
        return name;
    }
}

class Program
{
    static void Main()
    {
        Employee emp = new Employee("John", 50000.0);
        emp.SetSalary(55000.0);
        Console.WriteLine($"{emp.GetName()}'s salary is ${emp.GetSalary()}");
    }
}

In this example, the Employee class encapsulates the name and salary fields and provides public methods for setting and getting these values, allowing controlled access to the data.

---

## Lambdas
Lambdas are anonymous functions that can be used to create delegates or expression trees. They are useful for writing concise, inline functions.

Here is an example in C# code:

using System;
using System.Collections.Generic;

class Program
{
    static void Main()
    {
        List<int> numbers = new List<int> { 1, 2, 3, 4, 5 };

        // Using a lambda expression to find even numbers
        List<int> evenNumbers = numbers.FindAll(x => x % 2 == 0);

        Console.WriteLine("Even numbers:");
        evenNumbers.ForEach(num => Console.WriteLine(num));
    }
}

In this example, we use a lambda expression in the FindAll method to filter even numbers from a list.

---

## Interoperability
Interoperability refers to the ability of a programming language to work with other languages or systems. In C#, you can achieve interoperability by using platform invoke (P/Invoke) to call native functions in DLLs, or by using libraries like .NET Core's Platform Invocation Services (P/Invoke) or COM interop.

Here is an example in C# code:

using System;
using System.Runtime.InteropServices;

class Program
{
    [DllImport("user32.dll")]
    static extern int MessageBox(IntPtr hWnd, string text, string caption, uint type);

    static void Main()
    {
        MessageBox(IntPtr.Zero, "Hello, Interoperability!", "Message", 0x00000040);
    }
}

In this example, we use P/Invoke to call the MessageBox function from the user32.dll library, which is a Windows native function.

---

## Asynchronous Programming
Asynchronous programming allows you to write code that doesn't block the main thread, making your applications more responsive. In C#, you can use the async and await keywords to write asynchronous code.

Here is an example in C# code:

using System;
using System.Net.Http;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        await DownloadDataAsync();
    }

    static async Task DownloadDataAsync()
    {
        using (var client = new HttpClient())
        {
            string url = "https://jsonplaceholder.typicode.com/posts/1";
            HttpResponseMessage response = await client.GetAsync(url);

            if (response.IsSuccessStatusCode)
            {
                string content = await response.Content.ReadAsStringAsync();
                Console.WriteLine(content);
            }
        }
    }
}

In this example, we use asynchronous methods to download data from a web server without blocking the main thread, improving application responsiveness.