using System;

using System.Data;

using System.Xml;

​

namespace DataTableReaderDemonstration

{

    public static class Program

    {

        const string CONSOLE_MASK = "ID: {0}, First: {1}, Last: {2}, Birth Date: {3}";

        static string[] COLUMN_LIST = { "Id", "FirstName", "LastName", "Birthdate" };

​

        public static void Main()

        {

            Console.WriteLine("Demonstrate Dynamic Colulmn Positions\r\n");

            var dt = DataTableBuilder.GetSampleDataTable1();

            DisplayDataTable(dt);

            dt = DataTableBuilder.GetSampleDataTable2();

            DisplayDataTable(dt);

        }

​

        private static void DisplayDataTable(DataTable dt)

        {

            Console.WriteLine(dt.TableName);

            var reader = new DataTableReader(dt);

            var columnPointers = dt.GetColumnPointers(COLUMN_LIST);

            while (reader.Read())

            {

                Console.WriteLine(

                    CONSOLE_MASK,

                    reader.GetDbNullInt(columnPointers[0], 0),

                    reader.GetDbNullString(columnPointers[1], "First"),

                    reader.GetDbNullString(columnPointers[2], "Last"),

                    reader.GetDbNullDateTime(columnPointers[3], new DateTime(1900, 12, 31))

                    );

            }

            Console.WriteLine("");

        }

    }

​

    internal static class DataTableBuilder

    {

        internal static DataTable GetSampleDataTable1()

        {

            var result = new DataTable();

            result.TableName = "Sample Table 1";

            result.Columns.Add("Id", typeof(int));

            result.Columns.Add("FirstName", typeof(string));

            result.Columns.Add("LastName", typeof(string));

            result.Columns.Add("Birthdate", typeof(DateTime));

            result.Rows.Add(new object[] { DBNull.Value, DBNull.Value, DBNull.Value, DBNull.Value });

            result.Rows.Add(new object[] { 1, "Bill", "Bunion", new DateTime(2000, 1, 23) });

            result.Rows.Add(new object[] { 2, "Sally", "Smith", new DateTime(1999, 12, 31) });

            return result;

        }

​

        internal static DataTable GetSampleDataTable2()

        {

            var result = new DataTable();

            result.TableName = "Sample Table 2";

            result.Columns.Add("Id", typeof(int));

            result.Columns.Add("FirstName", typeof(string));

            result.Columns.Add("Initial", typeof(string));

            result.Columns.Add("LastName", typeof(string));

            result.Columns.Add("Country", typeof(string));

            result.Columns.Add("Birthdate", typeof(DateTime));

            result.Rows.Add(new object[] { DBNull.Value, DBNull.Value, DBNull.Value, DBNull.Value, DBNull.Value, DBNull.Value });

            result.Rows.Add(new object[] { 1, "Bill", "B", "Bunion", "USA", new DateTime(2000, 1, 23) });

            result.Rows.Add(new object[] { 2, "Sally", "S", "Smith", "Equador", new DateTime(1999, 12, 31) });

            return result;

        }

    }

​

    internal static class DataTableReaderExtensions

    {

        internal static int[] GetColumnPointers(this DataTable dt, string[] columnNameList)

        {

            var itemCount = columnNameList.Length;

            var result = new int[itemCount];

            if (itemCount > 0)

            {

                for (int i = 0; i < columnNameList.Length; i++)

                {

                    result[i] = dt.Columns[columnNameList[i]].Ordinal;

                }

            }

            return result;

        }

​

        internal static string GetDbNullString

        (

            this DataTableReader reader,

            int ordinalPosition,

            string valueIfNull

        )

        {

            var result = reader.IsDBNull(ordinalPosition)

                ? valueIfNull

                : reader.GetString(ordinalPosition);

            return result;

        }

​

        internal static int GetDbNullInt

        (

            this DataTableReader reader,

            int ordinalPosition,

            int valueIfNull

        )

        {

            var result = reader.IsDBNull(ordinalPosition)

                ? valueIfNull

                : reader.GetInt32(ordinalPosition);

            return result;

        }

​

        internal static DateTime GetDbNullDateTime

        (

            this DataTableReader reader,

            int ordinalPosition,

            DateTime valueIfNull

        )

        {

            var result = reader.IsDBNull(ordinalPosition)

                ? valueIfNull

                : reader.GetDateTime(ordinalPosition);

            return result;

        }

    }

}

​