为什么我的字符串值返回为 Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1[System.String]

Question

When I try to get value of SenderName and ReceiverName which are IQueryable<string> I see string Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1[System.String] on view.

Why I can't see my string value on db? Thanks.

I am using UnitOfWork pattern.

I can not reach the value of string my model properties

    using DAL;
    using Data.Model;
    using Microsoft.AspNetCore.Authorization;
    using Microsoft.AspNetCore.Mvc;
    using Microsoft.AspNetCore.Mvc.Rendering;
    using Microsoft.Extensions.Logging;
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Security.Claims;
    using System.Threading.Tasks;
    using TechEnabledSales.Models;

    namespace TechEnabledSales.Controllers
    {
        [Authorize(Roles = "100,200,1000")]
        public class InterviewController : Controller
        {
            private readonly IUnitOfWork _uow;
            private readonly ILogger<InterviewController> _log;

            public InterviewController(IUnitOfWork uow, ILogger<InterviewController> logger)
            {
                _uow = uow;
                _log = logger;
            }

            public IActionResult Index()
            {
                int.TryParse(this.User.FindFirstValue("ClinetId"), out int clientId);

                var repo = _uow.GetRepository<Interview>();
                var model = new List<InterviewVM>();
                model = repo.Single(predicate: f => f.ClientId == clientId)
                    .Select(s => new InterviewVM
                    {
                        SenderId = s.SenderId,
                        ClientId = s.ClientId,
                        Id = s.Id,
                        CreateDate = s.CreateDate,
                        Message = s.Message,
                        ReceiverId = s.ReceiverId,
                        ReceiverName = GetUserName(s.ReceiverId ?? 0),
                        SenderName = GetUserName(s.SenderId ?? 0)
                    }).ToList();

                ViewBag.Clients = null;
                if (this.User.IsInRole("200"))
                {
                    var repoClient = _uow.GetRepository<Clients>();
                    var clients = repoClient.GetList(size: 2000, orderBy: o => o.OrderBy(o2 => o2.Name)).Items
                            .Select(x => new SelectListItem()
                            {
                                Text = x.Name,
                                Value = x.Id.ToString()
                            });

                    ViewBag.Clients = new SelectList(clients, "Value", "Text", null);
                }

                return View(model);
            }

            [HttpPost]
            public IActionResult PostMessage(string message, int clientId2 = 0)
            {
                int.TryParse(this.User.FindFirstValue(ClaimTypes.NameIdentifier), out int userId);

                int.TryParse(this.User.FindFirstValue("ClinetId"), out int clientId);

                var repo = _uow.GetRepository<Interview>();
                var model = new Interview();
                model.ClientId = this.User.IsInRole("100") ? clientId : clientId2;
                model.Message = message;
                model.SenderId = this.User.IsInRole("200") ? userId : 0;
                model.ReceiverId = this.User.IsInRole("100") ? userId : 0;
                model.CreateDate = DateTime.Now;
                repo.Add(model, true);
                if (this.User.IsInRole("200"))
                    return Redirect("/Home/Index");
                else
                    return RedirectToAction("Index");
            }

            private IQueryable< string> GetUserName(int id)
            {
                if (id == 0)
                    return null;

                var repo = _uow.GetRepository<Users>();
                var model = repo.Single(predicate: u => u.Id == id).Select(s => string.Join(" ", s.FirstName, s.LastName));

                return model;
            }
        }
    }


    using System;
    using System.Collections.Generic;
    using System.Data.Common;
    using Microsoft.EntityFrameworkCore;

    namespace DAL
    {
        public interface IUnitOfWork : IDisposable
        {
            DbContext GetContext();
            List<T> RawSqlQuery<T>(string query, Func<DbDataReader, T> map);
            void ExecuteSql(string query);

            IRepository<TEntity> GetRepository<TEntity>() where TEntity : class;
            IRepositoryAsync<TEntity> GetRepositoryAsync<TEntity>() where TEntity : class;

            int SaveChanges();
        }

        public interface IUnitOfWork<TContext> : IUnitOfWork where TContext : DbContext
        {
            TContext Context { get; }
        }
    }

    using DAL.Paging;
    using Microsoft.EntityFrameworkCore.Query;
    using System;
    using System.Linq;
    using System.Linq.Expressions;

    namespace DAL
    {
        public interface IReadRepository<T> where T : class
        {        
            T Search(params object[] keyValues);
            IQueryable<T> Query(string sql, params object[] parameters);

            IQueryable<T> Single(Expression<Func<T, bool>> predicate = null,
                Func<IQueryable<T>, IOrderedQueryable<T>> orderBy = null,
                Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null,
                bool disableTracking = true);

            IPaginate<T> GetList(Expression<Func<T, bool>> predicate = null,
                Func<IQueryable<T>, IOrderedQueryable<T>> orderBy = null,
                Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null,
                int index = 0,
                int size = 50,
                bool disableTracking = true);

            IPaginate<TResult> GetList<TResult>(Expression<Func<T, TResult>> selector,
                Expression<Func<T, bool>> predicate = null,
                Func<IQueryable<T>, IOrderedQueryable<T>> orderBy = null,
                Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null,
                int index = 0,
                int size = 50,
                bool disableTracking = true) where TResult : class;
        }
    }

Answer 1

I recommend some changes for your code

// ... in InterviewController class

        public IActionResult Index()
        {
            // should check TryParse answer for false value to avoid latest error
            int.TryParse(this.User.FindFirstValue("ClinetId"), out int clientId);

            var targetClient = this._uow.GetRepository<Interview>()
                                   .Single(predicate: f => f.ClientId == clientId);
            // maybe BOOM cause DB don't contains such clientId -- should use try-catch

            // maybe should use AutoMapper instead of
            var model = new InterviewVM
            {
                SenderId = targetClient.SenderId,
                ClientId = targetClient.ClientId,
                Id = targetClient.Id,
                CreateDate = targetClient.CreateDate,
                Message = targetClient.Message,
                ReceiverId = targetClient.ReceiverId,
                ReceiverName = GetUserName(targetClient.ReceiverId ?? 0), // maybe should change contract of GetUserName
                SenderName = GetUserName(targetClient.SenderId ?? 0)
            };

            // ...
        }

        // ...

        private string GetUserName(int id)
        {
            if (id == 0) // What about other extreme values?
            {
                return null;
            }

            // should use try-catch
            var model = this._uow.GetRepository<Users>()
                            .Single(predicate: u => u.Id == id);

            return $"{model.FirstName} {model.LastName}";
        }
    }

// ...

    public interface IReadRepository<T> where T : class
    {
        T Search(params object[] keyValues);

        IQueryable<T> Query(string sql, params object[] parameters);

        T Single(Expression<Func<T, bool>> predicate = null,
            Func<IQueryable<T>, IOrderedQueryable<T>> orderBy = null,
            Func<IQueryable<T>, IIncludableQueryable<T, object>> include = null,
            bool disableTracking = true);

        // ... 
    }

Answer 2

 private IQueryable< string> GetUserName(int id) { if (id == 0) return null; var repo = _uow.GetRepository<Users>(); var model = repo.Single(predicate: u => u.Id == id).Select(s => string.Join(" ", s.FirstName, s.LastName)); return model; }

According to your code, the GetUserName() method returns a IQueryable< string> type value, so, if you directly display the result, it will show EntityQueryable1[System.String] , instead of the real user name.

I suggest you could try to change the InterviewVM model as below:

    public class InterviewVM
    {
        public string ReceiverName { get; set; }
        public string SenderName { get; set; }
        //... other properties
    }

Then, when you get the user Name, you could use FirstOrDefault().ToString() method to get the real user name from the IQueryable<string> result, code like this:

        model =repo.Single(predicate: f => f.ClientId == clientId)
            .Select(s => new InterviewVM
            {
                SenderId = s.SenderId,
                ClientId = s.ClientId,
                Id = s.Id,
                CreateDate = s.CreateDate,
                Message = s.Message,
                ReceiverId = s.ReceiverId,
                ReceiverName = GetUserName(s.ReceiverId ?? 0).FirstOrDefault().ToString(),
                SenderName = GetUserName(s.SenderId ?? 0).FirstOrDefault().ToString()
            }).ToList();

Besides, on my side, it seems that I can't use the select clause after Single method, so, I change the Single clause to where clause and use the FirstOrDefault() method to find the item.

code like this:

    public IActionResult Index2()
    {
        var result = interviews.Where(predicate: u => u.Id == 101).Select(s => new Interview()
        {
            Id = s.Id,
            Message = s.Message,
            ReceiverName = GetUserName(s.ReceiverId).FirstOrDefault().ToString(),
            SenderName = GetUserName(s.SenderId).FirstOrDefault().ToString()
        }).FirstOrDefault();

        return View(result);
    }
    private IQueryable<string> GetUserName(int id)
    {
        if (id == 0)
            return null;

        var repo = users;
        var model = repo.Where(predicate: u => u.Id == id).Select(s => string.Join(" ", s.FirstName, s.LastName)).AsQueryable();

        return model;
    }

The result like this: