CollapseAllButThis.cs

using System.ComponentModel.Composition;
using Microsoft.VisualStudio.Utilities;
using Microsoft.VisualStudio.Text.Editor;
using Microsoft.VisualStudio.Text.Outlining;
using System.Windows.Input;
using Microsoft.VisualStudio.Text;

namespace CollapseAllButThis
{
    [Export(typeof(IKeyProcessorProvider))]
    [ContentType("code")]
    [Name("CollapseAllButThisKeyProc")]
    [Order(Before = "VisualStudioKeyProcessor")]
    internal sealed class CollapseAllKeyProvider : IKeyProcessorProvider
    {
        [Import]
        internal IOutliningManagerService OutliningManagerService;

        public KeyProcessor GetAssociatedProcessor(IWpfTextViewHost wpfTextViewHost)
        {
            var outliningManager = OutliningManagerService.GetOutliningManager(wpfTextViewHost.TextView.TextViewModel);

            if (outliningManager != null)
                return new CollapseAllKeyProc(wpfTextViewHost.TextView, outliningManager);

            return null;
        }
    }

    internal sealed class CollapseAllKeyProc : KeyProcessor
    {
        private ITextView textView;
        private IOutliningManager outliningManager;

        public CollapseAllKeyProc(ITextView textView, IOutliningManager outliningManager)
        {
            this.textView = textView;
            this.outliningManager = outliningManager;
        }
        public override void KeyDown(KeyEventArgs args)
        {
            if (args.Key == Key.D1 &&
                (Keyboard.Modifiers & ModifierKeys.Control) != 0)
            {
                var point = textView.Caret.Position.BufferPosition;

                outliningManager.CollapseAll(new SnapshotSpan(textView.TextSnapshot, 0, textView.TextSnapshot.Length),
                    collapsible => !collapsible.Extent.GetSpan(textView.TextSnapshot).Contains(point));
            }
        }
    }
}