Question

首先，我运行下面的代码行以获取以下收益：（显示图像仅供参考）

var query_user1 = await _connection.QueryAsync<FavoritesProfile>("SELECT * FROM FavoritesProfile");

因此，我显然在我的数据表中将“ UsersProfileProfile”加载了User =“ Shane”和Titles =“ The Avengers”值。但是，当我尝试下一行代码时，会出现异常。

 var query_user = await _connection.QueryAsync<FavoritesProfile>("SELECT FROM FavoritesProfile WHERE User LIKE '%" + user + "%' AND Titles LIKE '%" + _movie.Title + "%'");

我确保用户是一个字符串，_movie.Title也是一个字符串。它们也分别对应于Shane和The Avengers。我还将添加该类中的所有代码，以防万一问题出在其他地方。如果您有任何见解，将不胜感激。我知道我不是以最干净的方式实现SQLite数据库。

    using Xamarin.Forms;
using System;
using MovieApp.Services;
using MovieApp.Models;
using SQLite;
using MovieApp.Persistance;

namespace MovieApp.Views
{
    public partial class MovieDetailsPage : ContentPage
    {
        private MovieService _movieService = new MovieService();
        private Movie _movie;
        private SQLiteAsyncConnection _connection;
        private string user = MainPage._username; //simplicity purposes as we didn't implement fully functions login page

        public class FavoritesProfile
        {
            [PrimaryKey, AutoIncrement]
            public int Id { get; set; }

            [MaxLength(255)]
            public string User { get; set; }

            [MaxLength(255)]
            public string Titles { get; set; }
        }
        public MovieDetailsPage(Movie movie)
        {
            if (movie == null)
                throw new ArgumentNullException(nameof(movie));

            _movie = movie;

            InitializeComponent();

            _connection = DependencyService.Get<ISQLiteDb>().GetConnection();
        }

        protected override async void OnAppearing()
        {
            var query_user1 = await _connection.QueryAsync<FavoritesProfile>("SELECT * FROM FavoritesProfile");
            //will create table if it does not already exist
            await _connection.CreateTableAsync<FavoritesProfile>();



            //BindingContext = await _movieService.GetMovie(_movie.Title);
            BindingContext =  _movie;

            CheckForFavoriteAsync();

            base.OnAppearing();
        }

        private async void CheckForFavoriteAsync()
        {
            try
            {
                var query_user = await _connection.QueryAsync<FavoritesProfile>("SELECT FROM FavoritesProfile WHERE User LIKE '%" + user + "%' AND Titles LIKE '%" + _movie.Title + "%'");
                if (query_user.Count >= 1)
                    favoriteicon.Icon = "star_filled.png";
            } catch (Exception) {

            }
        }

        public async void Favorite_Clicked(object sender, EventArgs e)
        {   

            if(favoriteicon.Icon == "star_filled.png")
            {
                //unadd from favorites  for user
                try
                {
                    var query_user = await _connection.QueryAsync<FavoritesProfile>("DELETE FROM FavoritesProfile WHERE User LIKE '%" + user + "%' AND Titles LIKE '%" + _movie.Title + "%'");
                } catch (Exception)
                {

                }

                favoriteicon.Icon = "star_unfilled.png";
            } 
            else
            {
                var query_user2 = await _connection.QueryAsync<FavoritesProfile>("SELECT * FROM FavoritesProfile");
                //add to favorites for user
                try
                {
                    var query_user = await _connection.QueryAsync<FavoritesProfile>("SELECT FROM FavoritesProfile WHERE User LIKE '%" + user + "%' AND Titles LIKE '%" + _movie.Title + "%'");
                } catch (Exception)
                {
                    var favorites = new FavoritesProfile { User = user, Titles = _movie.Title };
                    await _connection.InsertAsync(favorites);
                }

                favoriteicon.Icon = "star_filled.png";
            }


        }

    }
}

总体而言，我的Delete查询和通用的Select *查询一样有效，但是我无法过滤另一个查询并将结果返回给我。我只想在已有用户名和movieTitle条目的情况下得到结果，以便我可以填写图标向用户显示他们已经将该电影添加到收藏夹中。

Answer 1

第二个查询的SELECT语句无效。您需要指定要选择的列。

此行：

var query_user = await _connection.QueryAsync<FavoritesProfile>("SELECT FROM FavoritesProfile WHERE User LIKE '%" + user + "%' AND Titles LIKE '%" + _movie.Title + "%'");

可能应该是

var query_user = await _connection.QueryAsync<FavoritesProfile>("SELECT * FROM FavoritesProfile WHERE User LIKE '%" + user + "%' AND Titles LIKE '%" + _movie.Title + "%'");

QueryAsync没有提取正确的数据

1 个答案: