/// <summary>
        /// This function is used to get the contractor list from server
        /// </summary>
        private async void GetCompanyList()
        {
            IsBusy = true;
            var contractorLs = await _taskService.GetAllContractorList();

            if (contractorLs == null)
            {
                MessagingCenter.Send <ContractorListViewModel>(this, "GetContractorListFailed");
                IsBusy = true;
                return;
            }

            _fullCompanyList = new List <String>();
            for (int i = 0, len = contractorLs.Count; i < len; ++i)
            {
                _fullCompanyList.Add(contractorLs[i].contractorName);
            }

            ShowingCompanyList = _fullCompanyList;
            IsBusy             = false;
        }