//first form
    private void button1_Click(object sender, EventArgs e)
        {
        Form1 f2 = new Form1();
        f2.Text = comboBox2.Text;

        Form1 f3 = new Form1();
        f3.Text = comboBox1.Text;

        Form1 f4 = new Form1();
        f4.Text = textBox1.Text;

//second form
public partial class Form1 : Form
{

    private string text1;
    public string Text1
    {
        get { return text1; }
        set { Text1 = value; }
    }

    private string text2;
    public string Text2
    {
        get { return text2; }
        set { text2 = value; }
    }

    private string text3;
    public string Text3
    {
        get { return text3; }
        set { text3 = value; }
    }

    public Form1(Form1 frm1)
    {
        InitializeComponent();
    }

private void Form1_Load(object sender, EventArgs e)
    {

        string db = Text1;
        string user = Text2;
        string pass = Text3;

        String strConnection = @"Data Source=SERVER;Initial Catalog ="+db+"; User ID ="+user+"; Password ="+pass+";";
        SqlConnection con = new SqlConnection(strConnection);

        try
        {
            con.Open();
            SqlCommand sqlCmd = new SqlCommand();
            sqlCmd.Connection = con;
            sqlCmd.CommandType = CommandType.Text;
            sqlCmd.CommandText = "Select table_name  from information_schema.tables";
            SqlDataAdapter sqlDataAdap = new SqlDataAdapter(sqlCmd);
            DataTable dtRecord = new DataTable();
            sqlDataAdap.Fill(dtRecord);
            dtRecord.DefaultView.Sort = "table_name ASC";
            ComboBox1.DataSource = dtRecord;
            ComboBox1.DisplayMember = "TABLE_NAME";
            con.Close();
        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message);

            }