System.IO/WindowsRuntimeStreamExtensions.cs

Extension methods converting .NET Stream to Windows Runtime streams and vice versa.

// Source: https://github.com/unoplatform/uno | License: Apache-2.0
// Provided via justclaw.it.com; keep this notice with the code.
#nullable enable

using System.Threading;
using System.Threading.Tasks;
using Windows.Foundation;
using Windows.Storage.Streams;

namespace System.IO
{
	public static partial class WindowsRuntimeStreamExtensions
	{
		public static IInputStream AsInputStream(this Stream stream)
		{
			if (!stream.CanRead)
			{
				throw new NotSupportedException("Cannot convert stream to a IInputStream because stream does not support reading");
			}

			if (stream is IInputStreamWrapper wrapper
				&& wrapper.FindStream() is { } raw)
			{
				return raw;
			}

			return new InputStreamOverStream(stream);
		}

		public static IOutputStream AsOutputStream(this Stream stream)
		{

... (truncated -- full source via MCP)