C# Feature – using (statements & declarations)

Overview

using ensures IDisposable resources are disposed. C# 8 added using declarations and using var.

Introduced In

C# 1 (statement), C# 8 (declaration)

Before

var fs = File.OpenRead(path);
// remember to dispose later

After

using var fs = File.OpenRead(path); // disposed at end of scope

Annotated Example

// Classic statement
using (var stream = File.OpenRead(path))
{
  // use stream
}

// Declaration form (C# 8+)
using var stream2 = File.OpenRead(path);

Gotchas & Best Practices

• using declaration disposes at end of scope, not immediately.
• Prefer await using for IAsyncDisposable.

Related Features

• async/await