How add value to a label in user control?

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C#

Visual-Studio

Hi!

I have a registration form, a login form and a Main form.The program start with registration form. If i sign up the datas(name, email, password) load up to the local database. When i log in correctly show the main form. The main form has a usercontrol with a label. I would like to write a welcome text to the label with her/his name. Example: "Welcome Josh!". So I should to identify the user, so i use the textboxEmail.Text from the login form. It don't show the value.

What I have tried:

namespace personalFinance
{
   public partial class Login : Form
      {
        public Login()
         {

            InitializeComponent();
            var MainForm = new MainForm();
            MainForm.Show();
            HomepageUC hp = new 
            HomepageUC(textboxEmail.Text);
            hp.Show();
         } 
      }

}





public partial class HomepageUC : UserControl
{
   string login = "";

   public HomepageUC()
   {
       InitializeComponent();
   }

   public HomepageUC(string email): this() 
      {
       login = email;
        var conn = new SqlConnection(@"Server=(localdb)\MSSQLLocalDB; 
        AttachDbFileName=|DataDirectory|database.mdf;");
        conn.Open();
         try
            {
              conn.Open();
              var cmd = new SqlCommand($"SELECT name FROM registration_data WHERE email = '{login}'", conn);
               var reader = cmd.ExecuteReader();
               while (reader.Read()) labelWelcome.Text = reader[0].ToString();
            }
            
            finally
            {
                conn.Close(); 
            }
      }
 }