I am creating user profile logic for a blogging platform. I have the UserProfile model and then two separate models, UserSocialLink and SocialLinkType to control the user's various social media contacts (i.e. Facebook, Twitter, Google+, etc...). I am looking for feed back on the execution of the methods used to Add new UserProfiles. Is this the way you would handle it? Is there a better way? What are some of the issues you see with my methods (specifically in the service class)?

The Models

public class UserProfile
{
    public int Id { get; set; }
    public string UserName { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string ProfilePicUrl { get; set; }
    public string Location { get; set; }
    public string DateOfBirth { get; set; }
    public string Bio { get; set; }
    public DateTime Created { get; set; }
    public DateTime Updated { get; set; }
 }

public class UserSocialLink
{
    public int Id {get; set;}
    public int UserProfileId { get; set; }
    public int SocialLinkTypeID { get; set; }
    public string LinkValue { get; set; }
    public DateTime Created { get; set; }
    public DateTime Updated { get; set; }

    public virtual UserProfile UserProfile { get; set; }
    public virtual SocialLinkType SocialLinkType {get; set;}
}

public class SocialLinkType
{
    public int Id { get; set; }
    public string LinkType { get; set; }
    public string URLFormat { get; set; }
}

The Add Methods in The Service Class

public class UserProfileService : IUserProfileService
{
    public UserProfile Add(UserProfile userProfile)
    {
        var now = DateTime.UtcNow;
  
        if (userProfile == null)
            throw new ArgumentNullException("User Profile");

        userProfile.Created = now;
        userProfile.Updated = now;
        using (var db = new ApplicationDbContext())
        {
            db.UserProfiles.Add(userProfile);
            db.SaveChanges();
        }
        return userProfile;
    }

    public UserProfile AddSocialLink(string userName, UserSocialLink userSocialLink, string socialLinkType)
    {
        var now = DateTime.UtcNow;
        var userProfile = Get(userName);
        if (userProfile == null)
            throw new Exception("User Profile Not Found");
        using (var db = new ApplicationDbContext())
        {
            var linkType = db.SocialLinkTypes.SingleOrDefault(p => p.LinkType.ToUpper() == socialLinkType.ToUpper());
            if (linkType == null)
                throw new Exception("Social Media Type Not Found");
            userSocialLink.Created = now;
            userSocialLink.Updated = now;
            userSocialLink.SocialLinkTypeID = linkType.Id;
            db.UserSocialLinks.Add(userSocialLink);
            db.SaveChanges();
            return userProfile;
         }
    }
}