Share on facebook page with Xamarin (Requires "Facebook iOS SDK component")

AppDelegate.cs

using Facebook.CoreKit;

public override bool FinishedLaunching(UIApplication application, NSDictionary launchOptions)
{
	
	// Override point for customization after application launch.
	// If not required for your application you can safely delete this method

	return ApplicationDelegate.SharedInstance.FinishedLaunching (application, launchOptions);
}

public override bool OpenUrl (UIApplication application, NSUrl url, string sourceApplication, NSObject annotation)
{
	// We need to handle URLs by passing them to their own OpenUrl in order to make the SSO authentication works.
	return ApplicationDelegate.SharedInstance.OpenUrl (application, url, sourceApplication, annotation);
}

ViewController.cs

namespace socialtest.iOS
{
	public partial class ViewController : UIViewController
	{
		int count = 1;

		public ViewController(IntPtr handle) : base(handle)
		{		
		}

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

			// Perform any additional setup after loading the view, typically from a nib.
			Button.SetTitle("Login with facebook", UIControlState.Normal);
			Button.AccessibilityIdentifier = "myButton";
			Button.TouchUpInside += delegate {
				var loginManager = new LoginManager();
				var permissions = new string[] { "publish_actions" };
				loginManager.LogInWithPublishPermissions(permissions, this, (result, errors) => {
					// TODO Show success
				});
			};

			publish_button.TouchUpInside += delegate {
				var parameters = new NSDictionary("message", "This is a test message from Xamarin");
				var request = new GraphRequest("/<page_id>/feed", parameters, "POST");

				request.Start(delegate(GraphRequestConnection connection, NSObject result, NSError error) {
					if (error != null) {
						Console.WriteLine("Failed: " + error);
					}
				});
			};
		}

		public override void DidReceiveMemoryWarning()
		{		
			base.DidReceiveMemoryWarning();		
			// Release any cached data, images, etc that aren't in use.		
		}
	}
}