gistfile1.cs

var accountStore = new MonoTouch.Accounts.ACAccountStore();
var accType = accountStore.FindAccountType(ACAccountType.Facebook);
var accounts = accountStore.FindAccounts(accType);
var post = new NSString("Hello Facebook!");

if(accounts.Count() > 0)
{
	var accountType = accountStore.FindAccountType(ACAccountType.Facebook);

	accountStore.RequestAccess(accountType, null, (granted, error) => {
		if(granted)
		{
			var request = SLRequest.Create(SLServiceKind.Facebook,
				SLRequestMethod.Post,
				NSUrl.FromString("https://graph.facebook.com/me/feed"),
				NSDictionary.FromObjectAndKey(post, new NSString("message"))
			);

			var account = accountStore.FindAccounts(accountType).First();
			request.Account = account;
			request.PerformRequest((data, response, e) => {
				// Do something
			});
		}
		else
		{
		}

	});
}