public class conn
    {
        public String _pass;
        public String pass
        {
            get { return this._pass; }
            set { this._pass = value; }
        } 

        public String str_conn()
        {
            var connstr = new SqlConnectionStringBuilder();
            conn a=new conn();

            connstr.DataSource = "SQL";
            connstr.InitialCatalog = "project";
            connstr.UserID = "йй";
            connstr.Password = a.pass;

            return connstr.ToString();
        }


    }

        public String str_conn()
        {
            var connstr = new SqlConnectionStringBuilder();
           
            .....
            connstr.Password = pass;

            return connstr.ToString();
        }

        public String str_conn()
        {
            var connstr = new SqlConnectionStringBuilder();
           
            .....
            connstr.Password = pass;

            return connstr.ToString();
        }

conn a=new conn();

private void button2_Click(object sender, EventArgs e)
{
   conn c=new conn();
   c.login = textBox1.Text;
   c.psw = textBox2.Text;
   c.pass = textBox2.Text;
   //и куда там надо
   string cc = c.str_conn();
}

private string BuildConnectionString(string login, string password)
{
    var connectionStringBuilder= new SqlConnectionStringBuilder();

    connectionStringBuilder.DataSource = "SQL";
    connectionStringBuilder.InitialCatalog = "project";
    connectionStringBuilder.UserID = login;
    connectionStringBuilder.Password = password;

    return connectionStringBuilder.ToString();
}

private void button2_Click(object sender, EventArgs e)
{
    string cc = BuildConnectionString(textBox1.Text, textBox2.Text);
}

Форма ввода пароля:


        private void button2_Click(object sender, EventArgs e)
        {
 
            conn c=new conn();
            try
            {

                using (RegistryKey regSettings = Registry.CurrentUser.CreateSubKey("tehproject"))
                {
                    regSettings.SetValue("Login", textBox1.Text);
                    regSettings.SetValue("psw", textBox2.Text);
                    c.SqlConn();
                }
            }
            catch (System.Exception ex)
            {
                MessageBox.Show(ex.Message);
                Application.Exit();
            }


Классы, методы:


public class conn
    {

        public String login()
        {
            using (RegistryKey
                    regSettings = Registry.CurrentUser.CreateSubKey("tehproject"))
            {
                String l = regSettings.GetValue("Login").ToString();
                return l;
            }
        }

        public String psw()
        {
            using (RegistryKey
                    regSettings = Registry.CurrentUser.CreateSubKey("tehproject"))
            {
                String p = regSettings.GetValue("psw").ToString();
                return p;
            }
        }


        public String str_conn()
        {
            var connstr = new SqlConnectionStringBuilder();

            connstr.DataSource = "SQL";
            connstr.InitialCatalog = "project";
            connstr.UserID = login();
            connstr.Password = psw();

            return connstr.ToString();
        }

        public SqlConnection SqlConn()
        {
                SqlConnection connection = new SqlConnection(str_conn());
                connection.Open();
                return connection;
        }


     }



Вызов хранимых процедур:



    public class sql_exec
    {
        conn c1 = new conn();

        public int CreateCommand(String queryString, int id_par, String id_num, String id_name, DateTime date_to_sogl_gip, DateTime date_sogl_gip, DateTime date_confirm_doc, DateTime date_plan_doc_gip, DateTime date_el_send_doc, DateTime date_paper_send_doc)
        {
            using (c1.SqlConn())
            {
                SqlCommand command = new SqlCommand(queryString, c1.SqlConn());
                command.CommandType = CommandType.StoredProcedure;