Namespaces

Namespaces prevent name collisions and organize code logically:

```csharp

namespace MyApp.Models {

public class User {

public string Name { get; set; } = "";

}

}

namespace MyApp.Services {

using MyApp.Models; // bring User into scope

public class UserService {

public User Create(string name) => new User { Name = name };

}

}

```

---

File-Scoped Namespaces (C# 10+)

Removes one level of indentation — the namespace applies to the whole file:

```csharp

namespace MyApp.Models; // no braces needed

public class Product {

public string Name { get; set; } = "";

}

```

---

using Directives

```csharp

using System; // namespace import

using System.Collections.Generic;

using static System.Math; // import static members

using Alias = System.DateTime; // alias

double r = Sqrt(16); // from static import

Alias now = Alias.Now;

```

---

Global Usings (C# 10+)

Add to a single file (e.g., `GlobalUsings.cs`) and they apply project-wide:

```csharp

global using System;

global using System.Collections.Generic;

global using System.Linq;

```

---

Partial Classes

Split a class across multiple files — common in auto-generated code:

```csharp

// File1.cs

partial class Customer {

public string Name { get; set; } = "";

}

// File2.cs

partial class Customer {

public void Greet() => Console.WriteLine($"Hi, {Name}");

}

```

---

NuGet Packages

C#'s package manager. Install via CLI:

```bash

dotnet add package Newtonsoft.Json

dotnet add package Dapper

```

Or in `.csproj`:

```xml

<PackageReference Include="Newtonsoft.Json" Version="13.0.3" />

```

---

What's Next?

Your code is well-organized. Next: **concurrency** — async/await, Task, and parallel programming.