在我的 Xamarin 表单（跨平台）中使用 WCF Web 服务时出现错误

Question

Below is the error which I'm getting

Severity Code Description Project File Line Suppression State

Error CS1061 'Task<List<string>>' does not contain a definition for 'ToList' and no accessible extension method 'ToList' accepting a first argument of type 'Task<List<string>>' could be found (are you missing a using directive or an assembly reference?) LoginForm C:\Users\test\source\repos\LoginForm\LoginForm\LoginForm\MainPage.xaml.cs 26 Active

The data type selected while calling a web service was "System.Collections.Generic.List" for Collection type and for Dictionary collection type it was by default "System.Collections.Generic.Dictionary" .

Below is WCF webservice created

public List<string> LoginUserDetails(UserDetails userInfo)
        {
            List<string> usr = new List<string>();
            SqlConnection con = new SqlConnection("Data Source=Test; Initial Catalog=crm_db; User ID=sa;  Password=****");
            con.Open();
            SqlCommand cmd = new SqlCommand("select username,password from crm_tbl_admin where username=@UserName and password=@Password", con);
            cmd.Parameters.AddWithValue("@UserName", userInfo.UserName);
            cmd.Parameters.AddWithValue("@Password", userInfo.Password);

            SqlDataReader dr = cmd.ExecuteReader();

            if (dr.Read() == true)
            {
                usr.Add(dr[0].ToString());
            }
            con.Close();
            return usr;
        }
Below is the code for calling wcf in Xamarin's MainPage.Xaml.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using ServiceReference1;
using System.ServiceModel;

namespace WCF_LoginApp
{
    public partial class MainPage : ContentPage
    {
        Service1Client obj = new Service1Client();
        private static EndpointAddress endPoint = new EndpointAddress("http://localhost/ServiceLogin11/Service1.svc");
        private static NetTcpBinding binding;
        public MainPage()
        {
            InitializeComponent();
            binding = CreateBasicHttpBinding();
        }
        private static NetTcpBinding CreateBasicHttpBinding()
        {
            NetTcpBinding binding = new NetTcpBinding
            {
                Name = "netTcpBinding",
                MaxBufferSize = 2147483647,
                MaxReceivedMessageSize = 2147483647
            };

            TimeSpan timeout = new TimeSpan(0, 0, 30);
            binding.SendTimeout = timeout;
            binding.OpenTimeout = timeout;
            binding.ReceiveTimeout = timeout;
            return binding;
        }
        private void BtnLogin_Clicked(object sender, EventArgs e)
        {
            try
            {
                UserDetails userinfo = new UserDetails();
                userinfo.UserName = usernameEntry.Text;
                userinfo.Password = passwordEntry.Text;
                List<string> msg =  obj.LoginUserDetailsAsync(userinfo).ToList();
                //var result = obj.LoginUserDetailsAsync(userinfo);
                //string msg = result.ToString();
                messageLabel.Text = "Employee Name = " + msg.ElementAt(0);

            }
            catch (Exception ex)
            {
                // messageLabel.Text = "Wrong Id Or Password";
                throw ex;
            }
        }
    }
}

I'm new to mobile development, Here I'm trying to connect the remote database to Xamarin forms for user login using database credentials, Please help me out

Please help me Thanks in advance

Answer 1

you are calling an async method without using await

List<string> msg =  obj.LoginUserDetailsAsync(userinfo).ToList();

should be

var data =  await obj.LoginUserDetailsAsync(userinfo);
List<string> msg = data.ToList();

you will also need to add async to your method signature

private async void BtnLogin_Clicked(object sender, EventArgs e)