BindableToolbarItem.cs

// from https://forums.xamarin.com/discussion/comment/168974/#Comment_168974

public class BindableToolbarItem : ToolbarItem
    {
        public static readonly BindableProperty IsVisibleProperty =
            BindableProperty.Create("IsVisible", typeof (bool), typeof (BindableToolbarItem),
                true, BindingMode.TwoWay, propertyChanged: OnIsVisibleChanged);

        public BindableToolbarItem()
        {
            //InitVisibility();
        }

protected override void OnParentSet()
    {
        base.OnParentSet();
        InitVisibility();
    }
    
        public bool IsVisible
        {
            get { return (bool) GetValue(IsVisibleProperty); }
            set { SetValue(IsVisibleProperty, value); }
        }

        private void InitVisibility()
        {
            OnIsVisibleChanged(this, false, IsVisible);
        }

        private static void OnIsVisibleChanged(BindableObject bindable, object oldvalue, object newvalue)
        {
            var item = bindable as BindableToolbarItem;

            if (item != null && item.Parent == null)
                return;

            if (item != null)
            {
                var items = ((ContentPage) item.Parent).ToolbarItems;

                if ((bool) newvalue && !items.Contains(item))
                {
                    Device.BeginInvokeOnMainThread(() => { items.Add(item); });
                }
                else if (!(bool) newvalue && items.Contains(item))
                {
                    Device.BeginInvokeOnMainThread(() => { items.Remove(item); });
                }
            }
        }
        
// Usage: 

In your content pages attributes add this


xmlns:control="clr-namespace:Mobile.Controls"

#3. Add in your bindable toolbar items

<ContentPage.ToolbarItems>
       <control:BindableToolbarItem Text="Delete" Icon="delete.png" Command="{Binding DeleteCommand}" IsVisible="{Binding IsVisible}" />
  </ContentPage.ToolbarItems>