一對多的關係

UserType 屬於許多使用者< - >使用者有一個 UserType

單向導航屬性需要

public class UserType
{
    public int UserTypeId {get; set;}
}
public class User
{
    public int UserId {get; set;}
    public int UserTypeId {get; set;}
    public virtual UserType UserType {get; set;}
}

Entity<User>().HasRequired(u => u.UserType).WithMany().HasForeignKey(u => u.UserTypeId);

單向導航屬性可選（外來鍵必須是 Nullable 型別）

public class UserType
{
    public int UserTypeId {get; set;}
}
public class User
{
    public int UserId {get; set;}
    public int? UserTypeId {get; set;}
    public virtual UserType UserType {get; set;}
}

Entity<User>().HasOptional(u => u.UserType).WithMany().HasForeignKey(u => u.UserTypeId);

雙向導航屬性（必要/可選根據需要更改外來鍵屬性）

public class UserType
{
    public int UserTypeId {get; set;}
    public virtual ICollection<User> Users {get; set;}
}
public class User
{
    public int UserId {get; set;}
    public int UserTypeId {get; set;}
    public virtual UserType UserType {get; set;}
}

需要

Entity<User>().HasRequired(u => u.UserType).WithMany(ut => ut.Users).HasForeignKey(u => u.UserTypeId);

可選的

Entity<User>().HasOptional(u => u.UserType).WithMany(ut => ut.Users).HasForeignKey(u => u.UserTypeId);