try {
    conn.Open();
    // Perform query here
} finally {
    conn.Close();
}

connection.Open();
cmd.ExecuteReader(); // or any other form of getting the data
cmd2.ExecuteReader();
.
.
.
.
connection.Close();

using (SqlConnection connection =
                new SqlConnection(connectionString)
            {
                connection.Open();
                //issue command
            }