C# Fundamentals: .NET Development Guide

.NET basics, LINQ, async/await, ASP.NET, and Entity Framework intro with examples.

Why C# is a strong career language

C# is a modern, strongly typed language built for the .NET ecosystem. It powers enterprise backends, cloud services, desktop apps, Unity games, and APIs.

The language emphasizes clean syntax, tooling support, and robust object-oriented design.

Your first C# program

Hello C#

using System;

class Program
{
    static void Main()
    {
        Console.WriteLine("Hello, Rishtaara!");
    }
}

Understanding the .NET stack

.NET SDK gives you compiler and CLI tools.
CLR executes managed code and handles memory management.
NuGet provides package management for reusable libraries.

CLI workflow

Create and run a console app

dotnet new console -n RishtaaraApp
cd RishtaaraApp
dotnet run

Top-level statements style

Console.WriteLine("Quick start with top-level statements");

Classes, properties, and methods

C# supports encapsulation through access modifiers and properties. Properties are preferred over public fields for controlled access.

Basic class with property

public class Student
{
    public string Name { get; set; }
    public int Score { get; set; }

    public Student(string name, int score)
    {
        Name = name;
        Score = score;
    }

    public void PrintSummary()
    {
        Console.WriteLine($"{Name} scored {Score}");
    }
}

Inheritance and abstraction basics

Base classes share common behavior.
Abstract classes enforce implementation contracts.
Interfaces define capabilities independent of class hierarchy.

Why LINQ is powerful

LINQ (Language Integrated Query) lets you query collections using expressive, composable syntax. It improves readability and reduces boilerplate loops.

Filtering and projection with LINQ

Common LINQ operations

using System.Linq;

var scores = new List<int> { 78, 92, 85, 97 };

var topScores = scores.Where(s => s >= 90).ToList();
var doubled = scores.Select(s => s * 2).ToList();
var average = scores.Average();

Console.WriteLine(string.Join(", ", topScores));
Console.WriteLine(average);

Asynchronous programming model

async/await simplifies non-blocking code. It is essential for API calls, file I/O, and high-throughput server endpoints.

Task-based async example

Awaiting asynchronous work

using System.Net.Http;

static async Task<string> FetchAsync(string url)
{
    using var client = new HttpClient();
    return await client.GetStringAsync(url);
}

var content = await FetchAsync("https://example.com");
Console.WriteLine(content.Length);

ASP.NET Core in backend development

Build REST APIs with minimal APIs or controllers.
Use dependency injection and middleware pipeline.
Host microservices and cloud apps on Azure/AWS/on-prem.

Minimal API starter

First API endpoint

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.MapGet("/health", () => Results.Ok(new { status = "ok" }));
app.MapGet("/courses", () => new[] { "C#", "ASP.NET", "EF Core" });

app.Run();

ORM basics with EF Core

Entity Framework Core maps C# classes to database tables, so you can query data with LINQ instead of writing raw SQL for every operation.

DbContext and model setup

Simple EF Core model

public class AppDbContext : DbContext
{
    public DbSet<Student> Students => Set<Student>();

    public AppDbContext(DbContextOptions<AppDbContext> options) : base(options) {}
}

public class Student
{
    public int Id { get; set; }
    public string Name { get; set; } = "";
    public int Score { get; set; }
}

Query with LINQ

var toppers = await db.Students
    .Where(s => s.Score > 90)
    .OrderByDescending(s => s.Score)
    .ToListAsync();

Project scope

Build CRUD endpoints with ASP.NET Core.
Persist courses using EF Core.
Add async service methods.
Filter results using LINQ queries.

Project starter snippet

Course endpoint skeleton

app.MapPost("/courses", async (AppDbContext db, Course course) =>
{
    db.Add(course);
    await db.SaveChangesAsync();
    return Results.Created($"/courses/{course.Id}", course);
});

app.MapGet("/courses/{id:int}", async (AppDbContext db, int id) =>
{
    var course = await db.Set<Course>().FindAsync(id);
    return course is null ? Results.NotFound() : Results.Ok(course);
});

Key Takeaways

C# and .NET provide a full-stack ecosystem for modern apps.
OOP, LINQ, and async/await are essential C# productivity tools.
ASP.NET Core enables clean API design with powerful middleware.
EF Core streamlines database work using typed models and LINQ.
A project-oriented approach solidifies backend engineering fundamentals.

Frequently Asked Questions

Is C# only for Windows development?: No. Modern .NET is cross-platform and runs well on Linux, macOS, and Windows for web apps, APIs, and cloud services.
Should I learn LINQ before ASP.NET?: Yes. LINQ is used heavily in ASP.NET and EF Core projects, so understanding filtering, projection, and sorting early helps a lot.
Do I need SQL if I use EF Core?: Yes, at least basics. EF Core abstracts many queries, but SQL knowledge helps with performance tuning, debugging, and schema design.