在Visual Studio 2015中添加视图时发生错误

Question

所以我在应用程序中使用这些类。

 public class Expenses
 {
    public Category Category { get; set; }
    public PaymentModes PaymentModes { get; set; }
 }

 public class Category 
 {
    public int CategoryID { get; set; }
    public string CategoryName { get; set; }
 }

public class PaymentModes
 {
    public int PaymentModeID { get; set; }
    public string PaymentMode { get; set; }
 }

现在，当我在Details方法中添加视图时，它将引发以下错误。

 public ActionResult Details(int id)
 {
    return View();
 }

我该怎么办？

Answer 1

查看错误消息。明确地说，您没有为PaymentModes和Expenses模型类定义主键。请编写您的所有三个模型类，如下所示：

public class Category 
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int CategoryID { get; set; }
    public string CategoryName { get; set; }
}

public class PaymentModes
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int PaymentModeID { get; set; }
    public string PaymentMode { get; set; }
}

public class Expenses
{
     [Key, ForeignKey("Category"),Column(Order = 0)]
     public int CategoryID { get; set; }

     [Key, ForeignKey("PaymentModes"),Column(Order = 1)]
     public int PaymentModeID { get; set; }

     public Category Category { get; set; }

     public PaymentModes PaymentModes { get; set; }

}