return type must be 'bool' error c# : I have created application using xamarin android need to display and alert box , and based on the value selected I am doing some calculations. so on menu item click I have added below code.

       public override async Task<bool> OnOptionsItemSelected(IMenuItem item)
        {
            bool bTotalResult = false;
            switch (item.ItemId)
            {


                case Resource.Id.action_next:
                    bTotalResult = await ShowPayMentTypeDialog();

                    return await Task.Run(() => true).ConfigureAwait(true); ;
                default:
                    return await Task.Run(() => base.OnOptionsItemSelected(item)).ConfigureAwait(true);;
            }
            //return await Task.Run(() => false ).ConfigureAwait(true);
        }
        private async Task<bool> ShowPayMentTypeDialog()
        {
            bool bResult = false;
            try
            {
                LayoutInflater layoutInflater = LayoutInflater.From(this);
                View view = layoutInflater.Inflate(Resource.Layout.lyt_cash_credit_popup, null);
                Android.Support.V7.App.AlertDialog.Builder alertbuilder = new Android.Support.V7.App.AlertDialog.Builder(this);
                alertbuilder.SetView(view);
                var userdata = view.FindViewById<Spinner>(Resource.Id.spnrPaymentTerms);
                List<cls_spinner_adapter> resultsWayNo = new List<cls_spinner_adapter> {
                new cls_spinner_adapter {SZ_SPINNER_TEXT ="CASH"},
               new cls_spinner_adapter {SZ_SPINNER_TEXT ="CREDIT" } };
                CommonSpinnerAdapter paymentAdapter = new CommonSpinnerAdapter(this, resultsWayNo);
                userdata.Adapter = paymentAdapter;
                alertbuilder.SetCancelable(false)
                .SetPositiveButton("OK", delegate
                {
                    if (resultsWayNo[userdata.SelectedItemPosition].SZ_SPINNER_TEXT == "CASH")
                    {
                        cls_statics.B_IS_PROMOMAYMANET_CASH = true;
                    }
                    else
                    {
                        cls_statics.B_IS_PROMOMAYMANET_CASH = false;
                    }
                    bResult = true;
                })
                .SetNegativeButton("Cancel", delegate
                {
                    cls_statics.B_IS_PROMOMAYMANET_CASH = false;
                    bResult = true;
                    alertbuilder.Dispose();

                });
                Android.Support.V7.App.AlertDialog dialog = alertbuilder.Create();
                dialog.Show();
            }
            catch
            {

            }
            return await Task.Run(() => bResult).ConfigureAwait(true);
        }


But while compiling I am getting below  error.

  'return type must be 'bool' to match overridden member 'Activity.OnOptionsItemSelected(IMenuItem)'

Any help would be appreciated.