C#

SmtpClient client = new SmtpClient();
            client.Port = 587;
            client.Host = "smtp.gmail.com";
            client.EnableSsl = true;
            
            MailMessage mail = new MailMessage(new MailAddress("smanghnani23@gmail.com"), new MailAddress(TextBox2.Text));
            MailMessage mail1 = new MailMessage(new MailAddress("smanghnani23@gmail.com"), new MailAddress("smanghnani23@gmail.com"));
            mail.Subject = "Thank You For Submitting Your Request";
            mail1.Subject = "A New HIRING Request is Generated";
            mail1.Body = TextBox3.Text;
            mail.Body = "Thank you for registering with us";
            System.Net.NetworkCredential cred = new System.Net.NetworkCredential();
            cred.UserName = "smanghnani23@gmail.com";
            cred.Password = "password";
            client.Credentials = cred;
            client.Send(mail);
            client.Send(mail1);
            Label3.Visible = true;
            Label3.Text = "Send Succesfully";

try
 {
    // for MainTable ...
    OleDbConnection cnnSave=new OleDbConnection(myConnection);
    OleDbCommand cmd__AddRows = new OleDbCommand();
    cmd__AddRows.CommandText =
    @"INSERT INTO MainRegTable (IDMetal,NameMetal,FormulMetal, GroupMetal, CodeMetal,Comments)
    VALUES (@p1,@p2,@p3,@p4,@p5,@p6)";
    cmd__AddRows.Parameters.Clear();
    cmd__AddRows.Parameters.AddWithValue("@p1", txtID.Text);
    ....
   //for subTable ...
     OleDbDataAdapter dagrd = new OleDbDataAdapter(@"Select * From SubTblMetal
                                                    WHERE IDMetal=
                                                    "+int.Parse(txtID.Text),
                                                           cnnSave);
      DataSet dsGrd = new DataSet();
      dagrd.Fill(dsGrd, "SubTblMetal");
      dsGrd.GetChanges();
      dagrd.Update(dsGrd);
      dsGrd.AcceptChanges();

float[,] ctrlpoints = new float [4,3] {{ -4.0f, -4.0f, 0.0f }, { -2.0f, 4.0f, 0.0f },{ 2.0f, -4.0f, 0.0f }, { 4.0f, 4.0f, 0.0f }};

public partial class Form1 : Form
{
  public Form1()
  {
    InitializeComponent();
  }

  private void Form1_Load(object sender, EventArgs e)
  {
    Data data = new Data();

    string name = "Persons";
    Type type = data.GetType();
    PropertyInfo listProperty = type.GetProperty(name);

    //BindData<object>((List<object>)listProperty.GetValue(data, null));

    List<object> listObject = (List<object>)listProperty.GetValue(data, null);
  }

  private void BindData<T>(List<T> data)
  {
    comboBox1.DataSource = null;
    comboBox1.DataSource = data;
  }
}

public class Person
{
  public string Name { get; set; }
  public int Age { get; set; }

  public Person(string name, int age)
  {
    Name = name;
    Age = age;
  }

  public override string ToString()
  {
    return Name;
  }
}

public class Data
{
  public Data()
  {
    Persons = new List<Person>();
    Persons.Add(new Person("One", 1));
    Persons.Add(new Person("Two", 2));
  }

  public List<Person> Persons { get; set; }
}