SynchronousProgress.cs

namespace OaktreeLab.Utils.Common {
    /// <summary>
    /// Synchronous version of IProgress
    /// </summary>
    /// <typeparam name="T"></typeparam>
    public sealed class SynchronousProgress<T> : IProgress<T> {
        private readonly SynchronizationContext? _context;
        private readonly Action<T> _handler;

        public SynchronousProgress( Action<T> handler ) {
            _context = SynchronizationContext.Current;
            _handler = handler ?? throw new ArgumentNullException( nameof( handler ) );
        }

        /// <summary>
        /// Reports progress. Blocks until the handler has completed.
        /// </summary>
        /// <param name="value"></param>
        public void Report( T value ) {
            if ( _context == null ) {
                // No context: execute synchronously
                _handler( value );
                return;
            }
            if ( SynchronizationContext.Current == _context ) {
                // Already on UI thread: invoke directly
                _handler( value );
            } else {
                // Execute synchronously on the UI thread
                _context.Send( _ => _handler( value ), null );
            }
        }
    }
}