public partial class AdminUser
{
    public AdminUser()
    {
        RoleAssign = new HashSet<RoleAssign>();
    }

    public Guid UserId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string Email { get; set; }
    public string UserName { get; set; }
    public byte[] Password { get; set; }
    public DateTime CreatedTimeStamp { get; set; }
    public DateTime? ModifiedTimeStamp { get; set; }
    public DateTime? LogDate { get; set; }
    public short? LogNumber { get; set; }
    public bool ReloadActiveFlag { get; set; }
    public bool IsActive { get; set; }
    public string ExtraText { get; set; }
    public string ResetPasswordToken { get; set; }
    public DateTime? ResetPasswordTokenCreatedTimeStamp { get; set; }

    public virtual ICollection<RoleAssign> RoleAssign { get; set; }
}

public partial class RoleAssign
{
    public Guid RoleAssignId { get; set; }
    public Guid RoleId { get; set; }
    public Guid UserId { get; set; }

    public virtual AdminRole Role { get; set; }
    public virtual AdminUser User { get; set; }
}

modelBuilder.Entity<RoleAssign>(entity =>
{
    entity.Property(e => e.RoleAssignId).ValueGeneratedNever();

    entity.HasOne(d => d.Role)
        .WithMany(p => p.RoleAssign)
        .HasForeignKey(d => d.RoleId)
        .OnDelete(DeleteBehavior.ClientSetNull)
        .HasConstraintName("FK__RoleAssig__RoleI__160F4887");

    entity.HasOne(d => d.User)
        .WithMany(p => p.RoleAssign)
        .HasForeignKey(d => d.UserId)
        .OnDelete(DeleteBehavior.ClientSetNull)
        .HasConstraintName("FK__RoleAssig__UserI__17036CC0");
});

modelBuilder.Entity<AdminUser>(entity =>
{
    entity.HasKey(e => e.UserId);

    entity.Property(e => e.UserId).ValueGeneratedNever();

    entity.Property(e => e.CreatedTimeStamp)
        .HasColumnType("datetime")
        .HasDefaultValueSql("(getdate())");

    entity.Property(e => e.Email)
        .IsRequired()
        .IsUnicode(false);

    entity.Property(e => e.ExtraText).IsUnicode(false);

    entity.Property(e => e.FirstName)
        .IsRequired()
        .IsUnicode(false);

    entity.Property(e => e.IsActive)
        .IsRequired()
        .HasColumnName("isActive")
        .HasDefaultValueSql("((1))");

    entity.Property(e => e.LastName)
        .IsRequired()
        .IsUnicode(false);

    entity.Property(e => e.LogDate).HasColumnType("datetime");

    entity.Property(e => e.ModifiedTimeStamp).HasColumnType("datetime");

    entity.Property(e => e.Password).IsRequired();

    entity.Property(e => e.ResetPasswordToken).IsUnicode(false);

    entity.Property(e => e.ResetPasswordTokenCreatedTimeStamp).HasColumnType("datetime");

    entity.Property(e => e.UserName)
        .IsRequired()
        .IsUnicode(false);
});

public async Task<UserViewModel> AdminAuthentication(UserViewModel userView)
{
    var user = await _adminGenericRepository.FindAsync(x => x.IsActive && x.UserName.Equals(userView.UserName) && (AesEncryptAndDecrypt.DecryptStringFromBytes(x.Password, crytograpyKey, crytograpyIV).Equals(userView.Password)));

    if (user != null)
    {
        return new UserViewModel
        {
            UserId = user.UserId,
            isActive = user.IsActive,
            UserName = user.UserName,
            LastName = user.LastName,
            FirstName = user.FirstName,
            SelectedRole = mapRoleDbDataToViewModel(user.RoleAssign != null ? user.RoleAssign.FirstOrDefault().Role : null)
        };
    }
    return null;
}

private RoleViewModel mapRoleDbDataToViewModel(AdminRole dbRole)
{
    if (dbRole != null)
    {
        return new RoleViewModel
        {
            RoleId = dbRole.RoleId,
            RoleName = dbRole.RoleName,
            RoleType = dbRole.RoleType,
            SortOrder = dbRole.SortOrder,
            TreeLevel = dbRole.TreeLevel,
            Permissions = GetRuleByRoleId(dbRole.RoleId)
        };
    }
    return null;
}

public virtual async Task<T> FindAsync(Expression<Func<T, bool>> predicate)
{
    return await _entities.Set<T>().SingleOrDefaultAsync(predicate);
}

public IQueryable<T> FindBy(System.Linq.Expressions.Expression<Func<T, bool>> predicate)
{
    IQueryable<T> query = _entities.Set<T>().Where(predicate);
    return query;
}

string encryptedPassword = AesEncryptAndDecrypt.EncryptString(userView.Password, crytograpyKey, crytograpyIV);
var userData = await _adminGenericRepository.FindBy(x => x.IsActive && x.UserName == userView.UserName && x.Password == encryptedPassword)
    .Select( new
    {
        UserId = user.UserId,
        IsActive = user.IsActive,
        UserName = user.UserName,
        LastName = user.LastName,
        FirstName = user.FirstName,
        // When using FirstOrDefault, you should have an OrderBy to ensure the selection is predictable.
        SelectedRole = user.RoleAssign.OrderByDescending(x => x.Date).FirstOrDefault()?.Role
        // Cannot call C# methods here since this will go to SQL..
        // If you can populate a UserRoleViewModel in-line, then that can be put here to skip the extra mapping below.
    }).SingleOrDefaultAsync();

// At this point we will have the user details and it's selected Role ready for mapping.
//This assumes that the mapping of the Role does not rely on any child relationships under the Role.
if (userData != null)
    return new UserViewModel
    {
        UserId = userData.UserId,
        IsActive = userData.IsActive,
        UserName = userData.UserName,
        LastName = userData.LastName,
        FirstName = userData.FirstName,
        SelectedRole = mapRoleDbDataToViewModel(userData.SelectedRole)
    };
else
    return null;