DbDataReaderExtensions

DbDataReaderExtensions.cs

using System.Data.Common;
using System.Reflection;

namespace Demo.Extensions
{
    public static class DbDataReaderExtensions
    {
        public static T? Map<T>(this DbDataReader reader) where T : class, new()
        {
            // Check if the reader has rows
            if (reader.HasRows)
            {
                var properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);

                _ = reader.Read();

                T instanceToPopulate = new();

                foreach (var property in properties)
                {
                    var attribute = Attribute.GetCustomAttribute(property, typeof(DataFieldAttribute)) as DataFieldAttribute;
                    string columnName = attribute is not null ? attribute.Name : property.Name;

                    if (!reader.IsDBNull(reader.GetOrdinal(columnName)))
                    {
                        var type = Nullable.GetUnderlyingType(property.PropertyType) ?? property.PropertyType;
                        var safeValue = Convert.ChangeType(reader[columnName], type);
                        property.SetValue(instanceToPopulate, safeValue, null);
                    }
                }

                return instanceToPopulate;
            }

            return null;
        }

        public static List<T> MapToList<T>(this DbDataReader reader) where T : class, new()
        {
            var list = new List<T>();

            // Check if the reader has rows
            if (reader.HasRows)
            {
                var properties = typeof(T).GetProperties(BindingFlags.Public | BindingFlags.Instance);

                while (reader.Read())
                {
                    T instanceToPopulate = new();

                    foreach (var property in properties)
                    {
                        var attribute = Attribute.GetCustomAttribute(property, typeof(DataFieldAttribute)) as DataFieldAttribute;
                        string columnName = attribute is not null ? attribute.Name : property.Name;

                        if (!reader.IsDBNull(reader.GetOrdinal(columnName)))
                        {
                            var t = Nullable.GetUnderlyingType(property.PropertyType) ?? property.PropertyType;
                            object safeValue = Convert.ChangeType(reader[columnName], t);
                            property.SetValue(instanceToPopulate, safeValue, null);
                        }
                    }

                    list.Add(instanceToPopulate);
                }
            }

            return list;
        }
    }
}