How to populate ArrayList with SQL Select Statement Results

Question

I am doing an sql select statement on my web service in Visual Studio 2010. It is only from a column but there are multiple rows of data. How do I populate an arraylist with the data and return it?

[WebMethod]
        public List<String> getAccType(string bankId)
        {

            myConnection.Open();
            SqlDataReader myReader = null;
            SqlCommand myCommand = new SqlCommand("SELECT TypeName FROM AccType where BankID = '" + bankId + "'", myConnection);
            myReader = myCommand.ExecuteReader();
            List<String> AccType = new List<string>();
            while (myReader.Read())
            {
                string iAccType = myReader["TypeName"].ToString();
                AccType.Add(iAccType);

            }
            return AccType;

        }
    }

How do you fetch the data, using what? Pure ado.net or some orm perhaps? Here's how you work with an ArrayList: msdn.microsoft.com/en-us/library/… — von v.
– von v., Commented Jan 30, 2014 at 2:07
I would avoid using an ArrayList and, instead, use a strongly-typed List<T> containing the data. Especially since all the data is coming from the same column this should be preferred. — tvanfosson
– tvanfosson, Commented Jan 30, 2014 at 2:48

tvanfosson · Accepted Answer · 2014-01-30 02:56:49Z

While you could return an ArrayList, it would be better to return a strongly-typed collection, either a List<T> or IEnumerable<T> with an underlying List<T> collection, perhaps.

Here is an example using a SqlDataReader to extract data from a column and populate such a list. Note: I haven't included any error handling.

public IEnumerable<int> GetOrderIds()
{
    var ids = new List<int>();
    var queryString = "SELECT OrderID FROM dbo.Orders;";

    using (var connection = new SqlConnection(connectionString))
    using (var command = new SqlCommand(queryString, connection))
    {
        connection.Open();

        using (var reader = command.ExecuteReader())
        {
             while (reader.Read())
             {
                var id = reader.GetInt32(0);
                ids.Add(id);
             }
        }
    }

    return ids;
}

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