Zero/ZeroLevel.SQL/DBReader.cs

using System;
using System.Data;
using System.Data.Common;
using System.Linq;

namespace ZeroLevel.SqlServer
{
    public class DbReader
        : IDisposable
    {
        private readonly DbConnection _connection;
        private readonly IDbCommand _command;

        public DbReader(DbConnection connection, IDbCommand command)
        {
            _connection = connection;
            _command = command;
        }

        public IDataReader GetReader()
        {
            return _command.ExecuteReader(CommandBehavior.CloseConnection);
        }

        public void Dispose()
        {
            _command.Dispose();
            _connection.Close();
            _connection.Dispose();
        }
    }

    public static class DBReader
    {
        public static T Read<T>(this DbDataReader reader, int index)
        {
            if (reader == null || reader.FieldCount <= index || reader[index] == DBNull.Value) return default;
            Type t;
            if ((t = Nullable.GetUnderlyingType(typeof(T))) != null)
            {
                return (T)Convert.ChangeType(reader[index], t);
            }
            return (T)Convert.ChangeType(reader[index], typeof(T));
        }
        public static T Read<T>(this DbDataReader reader, string name)
        {
            if (reader == null || false == reader.GetColumnSchema().Any(c => c.ColumnName.Equals(name, StringComparison.OrdinalIgnoreCase)) || reader[name] == DBNull.Value) return default;
            Type t;
            if ((t = Nullable.GetUnderlyingType(typeof(T))) != null)
            {
                return (T)Convert.ChangeType(reader[name], t);
            }
            return (T)Convert.ChangeType(reader[name], typeof(T));
        }
        public static T Read<T>(this IDataReader reader, int index)
        {
            if (reader == null || reader.FieldCount <= index || reader[index] == DBNull.Value) return default;
            Type t;
            if ((t = Nullable.GetUnderlyingType(typeof(T))) != null)
            {
                return (T)Convert.ChangeType(reader[index], t);
            }
            return (T)Convert.ChangeType(reader[index], typeof(T));
        }
        public static T Read<T>(this IDataReader reader, string name)
        {
            if (reader == null || false == reader.HasColumn(name) || reader[name] == DBNull.Value) return default;
            Type t;
            if ((t = Nullable.GetUnderlyingType(typeof(T))) != null)
            {
                return (T)Convert.ChangeType(reader[name], t);
            }
            return (T)Convert.ChangeType(reader[name], typeof(T));
        }
        public static T Read<T>(this DataRow reader, int index)
        {
            if (reader == null || reader.ItemArray.Length <= index || reader.ItemArray[index] == DBNull.Value) return default;
            Type t;
            if ((t = Nullable.GetUnderlyingType(typeof(T))) != null)
            {
                return (T)Convert.ChangeType(reader.ItemArray[index], t);
            }
            return (T)Convert.ChangeType(reader.ItemArray[index], typeof(T));
        }
        public static T Read<T>(this DataRow reader, string name)
        {
            if (reader == null || false == reader.Table.Columns.Contains(name) || reader[name] == DBNull.Value) return default;
            Type t;
            if ((t = Nullable.GetUnderlyingType(typeof(T))) != null)
            {
                return (T)Convert.ChangeType(reader[name], t);
            }
            return (T)Convert.ChangeType(reader[name], typeof(T));
        }
        public static bool HasColumn(this IDataRecord dr, string columnName)
        {
            for (int i = 0; i < dr.FieldCount; i++)
            {
                if (dr.GetName(i).Equals(columnName, StringComparison.InvariantCultureIgnoreCase))
                    return true;
            }
            return false;
        }
    }
}