how to validate unique key

public class Branch
{
    [Key]
    public int Branch_code{ get; set; }
}


if that doesn't works try in this way 

Hi,
If you want to validate Branch_code field in View page you can define there or you can give validation message at model also.

In model you can define like this.

public class Employee {     [Required]     public string Name { get; set; }      [Required]     [Email]     public string Email{ get; set; } }