Getting Started with .NET

Learn how to set up your .NET development environment and create your first application.

What You'll Learn

• Installing the .NET SDK
• Understanding .NET versions
• Creating different project types
• Running and debugging applications

What is .NET?

.NET is a free, open-source, cross-platform framework created by Microsoft. It provides:

┌─────────────────────────────────────────────────────────┐
│                    .NET Components                       │
├─────────────────────────────────────────────────────────┤
│  Runtime (CLR)        │  Manages memory, executes code  │
│  Base Class Library   │  Common functionality           │
│  SDK                  │  Tools for development          │
│  Languages            │  C#, F#, VB.NET                 │
└─────────────────────────────────────────────────────────┘

Installing .NET

Download the SDK

Visit dotnet.microsoft.com/download or use package managers:

Windows

winget install Microsoft.DotNet.SDK.8

macOS

brew install dotnet-sdk

Linux (Ubuntu)

sudo apt-get update
sudo apt-get install -y dotnet-sdk-8.0

Verify Installation

# Check version
dotnet --version

# List installed SDKs
dotnet --list-sdks

# List installed runtimes
dotnet --list-runtimes

# Get help
dotnet --help

Your First Console App

Create the Project

# Create a new console application
dotnet new console -n HelloWorld

# Navigate to the project
cd HelloWorld

Examine the Code

// Program.cs
Console.WriteLine("Hello, World!");

Run the Application

dotnet run

Output:

Hello, World!

Your First Web API

Create the Project

# Create a Web API
dotnet new webapi -n MyApi

cd MyApi

Examine the Code

// Program.cs
var builder = WebApplication.CreateBuilder(args);

// Add services to the container
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

var app = builder.Build();

// Configure the HTTP request pipeline
if (app.Environment.IsDevelopment())
{
    app.UseSwagger();
    app.UseSwaggerUI();
}

app.UseHttpsRedirection();

// Sample endpoint
var summaries = new[]
{
    "Freezing", "Bracing", "Chilly", "Cool", "Mild",
    "Warm", "Balmy", "Hot", "Sweltering", "Scorching"
};

app.MapGet("/weatherforecast", () =>
{
    var forecast = Enumerable.Range(1, 5).Select(index =>
        new WeatherForecast
        (
            DateOnly.FromDateTime(DateTime.Now.AddDays(index)),
            Random.Shared.Next(-20, 55),
            summaries[Random.Shared.Next(summaries.Length)]
        ))
        .ToArray();
    return forecast;
})
.WithName("GetWeatherForecast")
.WithOpenApi();

app.Run();

record WeatherForecast(DateOnly Date, int TemperatureC, string? Summary)
{
    public int TemperatureF => 32 + (int)(TemperatureC / 0.5556);
}

Run the API

dotnet run

Visit https://localhost:5001/swagger to see the API documentation.

Project Templates

# List all available templates
dotnet new list

# Common templates
dotnet new console      # Console application
dotnet new webapi       # ASP.NET Core Web API
dotnet new mvc          # ASP.NET Core MVC
dotnet new blazor       # Blazor Web App
dotnet new worker       # Worker Service
dotnet new classlib     # Class library
dotnet new xunit        # xUnit test project
dotnet new gitignore    # .gitignore file

Common CLI Commands

Command	Description
dotnet new	Create a new project
dotnet build	Build the project
dotnet run	Build and run
dotnet test	Run tests
dotnet publish	Publish for deployment
dotnet add package	Add NuGet package
dotnet restore	Restore dependencies
dotnet clean	Clean build outputs

Development Tools

Visual Studio (Windows/Mac)

Full-featured IDE with:

• IntelliSense
• Debugger
• Designer tools
• Git integration

Visual Studio Code

Lightweight editor with C# extension:

# Install C# Dev Kit extension
code --install-extension ms-dotnettools.csdevkit

JetBrains Rider

Cross-platform professional IDE with:

• Advanced refactoring
• Code analysis
• Database tools

Hot Reload

.NET supports hot reload for faster development:

# Run with hot reload
dotnet watch run

Changes to code are automatically applied without restarting.

Complete Example

// Program.cs - Simple API with multiple endpoints
var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

// Simple endpoints
app.MapGet("/", () => "Welcome to my API!");

app.MapGet("/hello/{name}", (string name) =>
    $"Hello, {name}!");

app.MapGet("/api/time", () => new
{
    CurrentTime = DateTime.Now,
    TimeZone = TimeZoneInfo.Local.DisplayName
});

// Todo API
var todos = new List<Todo>();

app.MapGet("/api/todos", () => todos);

app.MapGet("/api/todos/{id}", (int id) =>
    todos.FirstOrDefault(t => t.Id == id) is Todo todo
        ? Results.Ok(todo)
        : Results.NotFound());

app.MapPost("/api/todos", (Todo todo) =>
{
    todo.Id = todos.Count + 1;
    todos.Add(todo);
    return Results.Created($"/api/todos/{todo.Id}", todo);
});

app.MapDelete("/api/todos/{id}", (int id) =>
{
    var todo = todos.FirstOrDefault(t => t.Id == id);
    if (todo is null) return Results.NotFound();

    todos.Remove(todo);
    return Results.NoContent();
});

app.Run();

record Todo
{
    public int Id { get; set; }
    public string Title { get; set; } = "";
    public bool IsComplete { get; set; }
}

Summary

You've learned:

• Installing and verifying .NET SDK
• Creating console and web API projects
• Running applications with dotnet run
• Common CLI commands
• Development tool options

Next Steps

Continue to Project Structure to understand .NET project organization!