How to retrieve the data from two tables in Sqlite in windows phone 8.1

I created two registration forms 1.User Registration 2.Company Registration (In one database)

I created a sign In page. How to retrieve the particular user from the tables.

class UserReg
{
    [AutoIncrement, PrimaryKey]
    public int UserID { get; set; }
    public string Name { get; set; }
    public string UserName { get; set; }
    public string UserPassword { get; set; }
    public string Gender { get; set; }
    public string State { get; set; }
}

The above code is for user registration table

class FuelReg
{
    [AutoIncrement,PrimaryKey]
    public int FuelID { get; set; }
    public string FuelName { get; set; }
    public string FuelPassword { get; set; }
    public string CompanyName { get; set; }
    public string CompanyAddress { get; set; }
}

The above code is for company registration.

Now the user and company should login with the same login page. How to implement this.

I tried some code but I cannot compare the particular user. My main problem is if the user and company provides similar user and password that would be a failure. So how to change it. (No validations given in the project)

private async void Button_Click_1(object sender, RoutedEventArgs e)
    {

        var dbpath = ApplicationData.Current.LocalFolder.Path + "/Map.db";
        var con = new SQLiteAsyncConnection(dbpath);
        try
        {
            UserReg t = new UserReg();
            string query = string.Format("select UserName,UserPassword,Gender,State,Name from UserReg where UserName='{0}' and UserPassword='{1}'", text_user.Text, text_pass.Password);

            List<UserReg> mylist = await con.QueryAsync<UserReg>(query);

            if (mylist.Count == 1)
            {
                t = mylist[0];
            }

            if (t.UserName == text_user.Text && t.UserPassword == text_pass.Password && t.Gender!=null && t.Name!=null && t.State!=null)
            {

                this.Frame.Navigate(typeof(MainPage));
            }
            else 
            {
                FuelReg f = new FuelReg();
                string query1 = string.Format("select FuelName,FuelPassword,CompanyName,CompanyAddress from FuelReg where FuelName='{0}' and FuelPassword='{1}'", text_user.Text, text_pass.Password);

                List<FuelReg> mylist1 = await con.QueryAsync<FuelReg>(query1);
                if (mylist1.Count == 1)
                {
                    f = mylist1[0];
                }

                if (f.FuelName == text_user.Text && f.FuelPassword == text_pass.Password && f.CompanyName!=null && f.CompanyAddress!=null)
                {

                    this.Frame.Navigate(typeof(NewPage));
                }
            }
        }
        catch(Exception ex)
        {
            var msd = new MessageDialog("" + ex).ShowAsync();
        }

    }

So how to fetch the exact data when the user inputs in the SignIn page from the two tables