Snapped Horizontal UICollectionView in Xamarin.iOS

SnapLayout.cs

namespace SnapCollection
{
	using UIKit;
	using CoreGraphics;

	public class SnapLayout : UICollectionViewFlowLayout
	{
		public SnapLayout()
		{
			this.ItemSize = new CGSize(300, 250);
			this.ScrollDirection = UICollectionViewScrollDirection.Horizontal;
		}


		CGPoint mostRecentOffset = new CGPoint();

		public override CGPoint TargetContentOffset(CGPoint proposedContentOffset, CGPoint scrollingVelocity)
		{
			if(scrollingVelocity.X == 0)
			{
				return mostRecentOffset;
			}

			var cv = this.CollectionView;
			if(cv != null)
			{
				var cvBounds = this.CollectionView.Bounds;
				var halfWidth = cvBounds.Size.Width * 0.5f;
				var attributesForVisibleCells = this.LayoutAttributesForElementsInRect(cvBounds);
				if(attributesForVisibleCells != null)
				{
					if (proposedContentOffset.X == -(cv.ContentInset.Left))
					{
						return proposedContentOffset;
					}

					UICollectionViewLayoutAttributes candidateAttributes = null;
					foreach (var attributes in attributesForVisibleCells)
					{
						if (attributes.RepresentedElementCategory != UICollectionElementCategory.Cell) 
						{
							continue;
						}

						if ((attributes.Center.X == 0) || (attributes.Center.X > (cv.ContentOffset.X + halfWidth) && scrollingVelocity.X < 0)) {
							continue;
	
						}
						candidateAttributes = attributes;
					}

					if(candidateAttributes == null)
					{
						return mostRecentOffset;
					}

					return mostRecentOffset = new CGPoint(candidateAttributes.Center.X - halfWidth, proposedContentOffset.Y);
				}
			}

			return mostRecentOffset = base.TargetContentOffset(proposedContentOffset, scrollingVelocity);
		}
	}
}

ViewController.cs

namespace SnapCollection
{
	using System;
	using UIKit;

	public partial class ViewController : UIViewController
	{
		protected ViewController(IntPtr handle) : base(handle) { }

		public override void ViewDidLoad()
		{
			base.ViewDidLoad();

			this.collectionView.CollectionViewLayout = new SnapLayout();
			this.collectionView.Source = new Source();
			this.collectionView.DecelerationRate = UIScrollView.DecelerationRateFast;

			var insets = this.collectionView.ContentInset;
			insets.Left = 10;
			insets.Right = 10;
			this.collectionView.ContentInset = insets;

		}
	}
}

Translated from http://blog.karmadust.com/centered-paging-with-preview-cells-on-uicollectionview/