An exception of type 'System.Data.Entity.ModelConfiguration.ModelValidationException' occurred in EntityFramework.dll

Question

Error-An exception of type 'System.Data.Entity.ModelConfiguration.ModelValidationException' occurred in EntityFramework.dll but was not handled in user code Additional information: One or more validation errors were detected during model generation: MVCApplication.Models.Employee: : EntityType 'Employee' has no key defined. Define the key for this EntityType. Employees: EntityType: EntitySet 'Employees' is based on type 'Employee' that has no keys defined.

controller code:

namespace MVCApplication.Controllers
{
    public class EmployeeController : Controller
    {
        // GET: Employee
        public ActionResult Detail(int id)
        {
            EmployeeContext employeecontext = new EmployeeContext();
            Employee emp = employeecontext.Employees.Single(x => x.Emp_Id ==id);//here its throwing an exception
            return View("employee",emp);
        }
    }

this is my model employee class:

namespace MVCApplication.Models
{
    [Table("Employee")]
    public class Employee
    {
        public int Emp_Id { get; set; }
        public string Emp_Name { get; set; }
        public string Designation { get; set; }
        public string City { get; set; }
        public string State { get; set; }
        public string Country { get; set; }
    }
}

this is my employee context class:

namespace MVCApplication.Models
{
    public class EmployeeContext : DbContext
    {
        public DbSet<Employee> Employees { get; set; }
    }
}

Answer 1

You have to set attribute [Key] to your model, like this

[Table("Employee")]
public class Employee
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Key]
    public int Emp_Id { get; set; }
    public string Emp_Name { get; set; }
    public string Designation { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string Country { get; set; }
}

Use [DatabaseGenerated(DatabaseGeneratedOption.Identity)] only if your database generate ids, if not you just [Key] attribute.

Answer 2

Make sure that you have set the auto increment attribute to 'Emp_Id' column in your database table, and your model should look like this:

[Table("Employees")]
public class Employee
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Key]
    public int Emp_Id { get; set; }
    public string Emp_Name { get; set; }
    public string Designation { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string Country { get; set; }
}