CustomEntryRenderer.cs

using System;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly: ExportRenderer(typeof(Entry), typeof(MyCoolApp.iOS.CustomEntryRenderer))]
namespace MyCoolApp.iOS {
  public class CustomEntryRenderer : EntryRenderer {
    protected override void OnElementChanged(ElementChangedEventArgs<Entry> e) {
      base.OnElementChanged(e);
      if (this.Control != null) {
        this.Control.AutocapitalizationType = UIKit.UITextAutocapitalizationType.None;
        this.Control.AutocorrectionType = UIKit.UITextAutocorrectionType.No;
      }
    }
  }
}