C#

if (Sender is form1)
    {
    form1 temp = (form1)Sender;
    form1.login()
}

class Login
    {
    //strings and ints here
    Form CurrentForm;

public class MyForm1 : Form, IMyCommonFormFunctionality { ... }

public interface IMyCommonFormFunctionality {
    void login();
}

IMyCommonFormFunctionality CurrentForm;
...
CurrentForm=sender as IMyCommonFormFunctionality;

MySqlConnection connection = new MySqlConnection(MyConString);
MySqlCommand command = connection.CreateCommand();
try
{
    connection.Open();
    Console.WriteLine("Connected to DB");
}
catch (Exception e)
{
    Console.WriteLine("Failed to connect to DB");
    return;
}
command.CommandText = "truncate table test_tb";
command.ExecuteNonQuery();
connection.Close();


StreamReader sr = new StreamReader("somefile.txt", Encoding.GetEncoding(1251));
string line, query;
string[] data;
byte[] temp = new byte[10000];
int j = 0;
while ((line = sr.ReadLine()) != null && j < 10)
{
    data = line.Split('~');

    query = "insert into test_tb (name, id) values(N'" + data[2] + "'," + j.ToString() + ")";
    /*Some parsing was done here, data[2] contains 1251 encoded string*/
    temp = ASCIIEncoding.GetEncoding(1251).GetBytes(query);
    command.CommandText = ASCIIEncoding.GetEncoding(1251).GetString(temp);
    connection.Open();
    command.ExecuteNonQuery();
    connection.Close();
    ++j;
}

protected virtual void OnClick(EventArgs e)

// UserControl with TextBox dropped on and handlng the textBox's Click event
public partial class MyUserControl : UserControl
{
    public MyUserControl()
    {
        InitializeComponent();
    }

    private void textBox_Click(object sender, EventArgs e)
    {
        OnClick(e);
    }
}

//Form with MyUserControl dropped on and handling the myUserControl's Click event
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }

    private void myUserControl_Click(object sender, EventArgs e)
    {
        MessageBox.Show("Click Event");
    }
}