c# - 使用 Entity Framework 从数据库中检索数据

Question

我是 Entity Framework 的初学者。我正在构建一个 WPF 应用程序。以下是我的模型类:

[Table("Vehicle")]
    public class Vehicle
    {
        [Key]
        public int VehicleId { get; set; }
        [Column("LicencePlateNumber", TypeName = "ntext")]
        [MaxLength(100)]
        public string LicencePlateNumber { get; set; }
        [Column("LicencePlateState", TypeName = "ntext")]
        [MaxLength(100)]
        public string LicencePlateState { get; set; }
        [Column("Make", TypeName = "ntext")]
        [MaxLength(100)]
        public string Make { get; set; }
        [Column("Other", TypeName = "ntext")]
        [MaxLength(100)]
        public string Other { get; set; }
        [Column("Model", TypeName = "ntext")]
        [MaxLength(100)]
        public string Model { get; set; }
        [Column("Style", TypeName = "ntext")]
        [MaxLength(100)]
        public string Style { get; set; }
        [Column("Color", TypeName = "ntext")]
        [MaxLength(100)]
        public string Color { get; set; }
        [Column("PurchaseYear", TypeName = "int")]
        public int PurchaseYear { get; set; }
        [Column("InsurnaceCompanyName", TypeName = "ntext")]
        [MaxLength(100)]
        public string InsurnaceCompanyName { get; set; }
        [Column("InsurnaceCompanyNumber", TypeName = "ntext")]
        [MaxLength(100)]
        public string InsurnaceCompanyNumber { get; set; }
    }

我正在尝试从数据网格中的这个表中检索数据。

 using (var context = new TransportContext())
 {                
       var vehicleList = from v in context.Vehicles
                         select new
                         {
                              Number = v.LicencePlateNumber,
                              Make = v.Make,
                              Model = v.Model,
                              Year = v.PurchaseYear
                         };
                    DG_Details.ItemsSource = vehicleList;
                    DG_Details.Items.Refresh();
   }

但我得到了一个 XAMLParseException。另一方面，如果我尝试这样做，它就会起作用:

 using (var context = new TransportContext())
 {              
       var projectionQuery = from v in context.Vehicles
                                  select v;
            var vehicleList = projectionQuery.ToList<Vehicle>();
                    DG_Details.ItemsSource = vehicleList;
                    DG_Details.Items.Refresh();
   }

但我只想检索 4 列而不是全部。需要帮忙!!

Answer 1

试试这个:

var vehicleList = (from v in context.Vehicles
                         select new
                         {
                              Number = v.LicencePlateNumber,
                              Make = v.Make,
                              Model = v.Model,
                              Year = v.PurchaseYear
                         }).ToList();
                    DG_Details.ItemsSource = vehicleList;
                    DG_Details.Items.Refresh();