Error occoured while adding view in Visual Studio 2015

Question

So I am using these classes in my application.

 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; }
 }

Now when I add view in Details method it throws below error.

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

What should I do?

Answer 1

Look at the error message. Its clearly saying that you don't primary key defined for the PaymentModes and Expenses model classes. Please write your all three model classes as follows:

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; }

}