How can get sum for _price ?

private async Task GeReceipts()
        {
            receiptData = new List();
            UserDialogs.Instance.ShowLoading("", MaskType.Clear);
            receiptData = await GetReceiptsData.GetReceipts_Data(olcID, _status);
            UserDialogs.Instance.HideLoading();
            if (receiptData.Count() >= 0)
            {
                countrows = receiptData.Count();
                _msdins = receiptData.Select(element => element.MSIDN).ToArray();
                _price = receiptData.Select(element => element.Price).ToArray();
                return true;
            }
            else
                return false;
        }