Xamarin.iOS の Tutorial をなんとなくトレースしてみる ref: http://qiita.com/items/bac6621007ecfe7dddb9

file0.m

@property (retain, nonatomic) IBOutlet UIButton *btnClickMe;

file2.m

- (IBAction)actnButtonClick:(id)sender;

HelloWorld_iPhoneViewController.cs

namespace HelloWorld_iPhone
{
    public partial class HelloWorld_iPhoneViewController : UIViewController
    {
        protected int _numberOfTimesClicked = 0;

        <省略>

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

            // Perform any additional setup after loading the view, typically from a nib.
            btnClickMe.TouchUpInside += (sender, e) => 
            {
                _numberOfTimesClicked++;
                lblOutput.Text = "Clicked [" +
                    _numberOfTimesClicked.ToString() + "] times!";
            };
        }

        <省略>

        partial void actnButtonClick(NSObject sender)
        {
            lblOutput.Text = "Action button " +  ((UIButton)sender).CurrentTitle + " clicked.";
        }
    }
}

HelloWorld_iPhoneViewController.designer.cs

using MonoTouch.Foundation;

namespace HelloWorld_iPhone
{
    [Register ("HelloWorld_iPhoneViewController")]
    partial class HelloWorld_iPhoneViewController
    {
        [Outlet]
        MonoTouch.UIKit.UIButton btnClickMe { get; set; }

        void ReleaseDesignerOutlets ()
        {
            if (btnClickMe != null) {
                btnClickMe.Dispose ();
                btnClickMe = null;
            }
        }
    }
}