Unmanaged resources

Context: Unmanaged resources are resources that the .NET GC does not know about. Examples include file handles, window handles (HWND), GDI objects, database connections, network sockets, and memory allocated via Marshal.AllocHGlobal. These resources must be explicitly released by the developer. IDisposable is the standard pattern for releasing them.

Usage Example

using System;
using System.Runtime.InteropServices;

public class NativeBuffer : IDisposable
{
    private IntPtr _buffer;
    private bool _disposed = false;

    public NativeBuffer(int size)
    {
        _buffer = Marshal.AllocHGlobal(size);
    }

    public void Dispose()
    {
        if (!_disposed && _buffer != IntPtr.Zero)
        {
            Marshal.FreeHGlobal(_buffer);
            _buffer = IntPtr.Zero;
            _disposed = true;
        }
        GC.SuppressFinalize(this);
    }

    ~NativeBuffer()
    {
        if (_buffer != IntPtr.Zero)
        {
            Marshal.FreeHGlobal(_buffer);
        }
    }
}

Output console

// No output; the native memory is freed when Dispose() is called.

Important notes

• Unmanaged resources cause resource leaks if not released.
• Always provide a finalizer (destructor) as a backup.

Real‑world usage example

Native memory allocator – When using Marshal.AllocHGlobal for interop, wrap it in an IDisposable class to ensure memory is freed.
See .NET docs on unmanaged resources.

Related sections

• 10.2 IDisposable
• 10.2.2 Dispose pattern