How to add a Primary and Foreign Key Relationship with Code First in Entity Framework

This article will demonstrate how to implement primary key and foreign key relationship in Code First approach in Entity Framework.

To complete this task, I am going to create Employee and Department Model Class and let’s see how to make relationship. Following are the two model class. 

public class Department  
{  
   [Key]  
   public int DepartmentId { get; set; }  
  
   [Required]  
   public string DepartmentName { get; set; }  
}  
  
public class Employee  
{  
   [Key]  
   public int EmployeeId { get; set; }  
  
   [Required]  
   public string EmployeeName { get; set; }  
  
}  

Department Model has primary key as DepartmentId and Employee Model has primary key as EmployeeId. I am going to create a foreign key of DepartmentId in Employee Model.

public class Department  
{  
   [Key]  
   public int DepartmentId { get; set; }  
  
   [Required]  
   public string DepartmentName { get; set; }  
}  
  
public class Employee  
{  
   [Key]  
   public int EmployeeId { get; set; }  
  
   [Required]  
   public string EmployeeName { get; set; }  
  
   // Foreign key   
   [Display(Name = "Department")]  
   public virtual int DepartmentId { get; set; }  
  
   [ForeignKey("DepartmentId")]  
   public virtual Department Departments { get; set; }  
}  

To create Foreign Key, you need to use ForeignKey attribute with specifying the name of the property as parameter. 

[ForeignKey("DepartmentId")]  
public virtual Department Departments { get; set; }  

You also need to specify the name of the table which is going to participate in relationship. I mean to say, define the foreign key table.

[Display(Name = "Department")]  
public virtual int DepartmentId { get; set; }  

Thanks for reading this article, hope you enjoyed it.