Making sure a SQL db connection is always closed after each repo function is called

Question

I am trying to figure out whether I need a using statement in each of my repository functions in order to make sure the connection closes after each batch of database calls.

For example: I want to call connection.query or connection.execute multiple times inside of certain repository functions. If I don't use a using statement when will my connection ever close? The goal is to make it as efficient as possible for web development.

BaseRepository

public static string ConnectionString => @"Server=.;Database=applicationDb;User ID=sa;Password=Password12!";
protected SqlConnection _connection;
protected SqlConnection connection => _connection ?? (_connection = GetOpenConnection());

public static SqlConnection GetOpenConnection(bool mars = false)
{
    var cs = ConnectionString;
    if (mars)
    {
        var scsb = new SqlConnectionStringBuilder(cs)
        {
            MultipleActiveResultSets = true
        };
        cs = scsb.ConnectionString;
    }
    var connection = new SqlConnection(cs);
    connection.Open();
    return connection;
}

public SqlConnection GetClosedConnection()
{
    var conn = new SqlConnection(ConnectionString);
    if (conn.State != ConnectionState.Closed) throw new InvalidOperationException("should be closed!");
    return conn;
}

public void Dispose()
{
    _connection?.Dispose();
}

CustomerRepository : BaseRepository

With the BaseRepository setup the way it is. Is there any difference between the following:

public IEnumerable<Customer> GetCustomers()
{
    using (connection)
    {
        StringBuilder sql = new StringBuilder();
        sql.AppendLine("SELECT Id, Name, Email ");
        sql.AppendLine("FROM Customer;");

        StringBuilder deleteSql = new StringBuilder();
        deleteSql = new StringBuilder();
        deleteSql.AppendLine("DELETE FROM Xyz ");
        deleteSql.AppendLine("FROM CustomerId = @CustomerId;");
        connection.Execute(deleteSql.ToString(), new { CustomerId = 5 });

        return connection.Query<Customer>(sql.ToString()).ToList();
    }
}

OR without the using:

public IEnumerable<Customer> GetCustomers()
{
        StringBuilder sql = new StringBuilder();
        sql.AppendLine("SELECT Id, Name, Email ");
        sql.AppendLine("FROM Customer;");

        StringBuilder deleteSql = new StringBuilder();
        deleteSql = new StringBuilder();
        deleteSql.AppendLine("DELETE FROM Xyz ");
        deleteSql.AppendLine("FROM CustomerId = @CustomerId;");
        connection.Execute(deleteSql.ToString(), new { CustomerId = 5 });

        return connection.Query<Customer>(sql.ToString()).ToList();
}

Answer 1

You need to wrap your calls in using statement (or try...catch if you wish to handle the exceptions), and it will close it and dispose it automatically.