PetaPoco value converters using PetaPoco.ConventionMapper

PetaPocoValueConverter.cs

using System;
using System.Drawing;

namespace PetaPoco
{

    /// <summary>
    /// Specifies a persistent property value converter.
    /// </summary>
    [AttributeUsage(AttributeTargets.Property)]
    public abstract class ValueConverterAttribute : Attribute
    {
        public abstract object ConvertToDb(object value);
        public abstract object ConvertFromDb(object value);

    }

    /// <summary>
    /// Converter for storing Color as INT32 in database
    /// </summary>
    public class ColorValueConverterAttribute : ValueConverterAttribute
    {
        public override object ConvertToDb(object value)
        {
            if (!(value is Color)) return null;
            return ((Color)value).ToArgb() & 0x00FFFFFF;
        }
        public override object ConvertFromDb(object value)
        {
            if (!(value is Int32)) return null;
            return Color.FromArgb((Int32)value | /* 0xFF000000 */ -16777216);
        }
    }

    /// <summary>
    /// Converter for storing image as VARBINARY in database.
    /// </summary>
    public class ImageValueConverterAttribute : ValueConverterAttribute
    {
        public override object ConvertToDb(object value)
        {
            if (value == null || !(value is Image)) return null;
            ImageConverter ic = new ImageConverter();
            return ic.ConvertTo(value, typeof(byte[]));
        }
        public override object ConvertFromDb(object value)
        {
            if (value == null) return null;
            ImageConverter ic = new ImageConverter();
            return ic.ConvertFrom(value);
        }
    }

}

PetaPocoValueConverterExample.cs

// Example of using ValueConverterAttributes

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;

namespace PPTest
{
    [PetaPoco.ExplicitColumns]
    class ItemReason
    {
        [PetaPoco.Column]
        public int ItemReasonID { get; set; }
        [PetaPoco.Column]
        public string Name { get; set; }

        [PetaPoco.Column]
        [PetaPoco.ColorValueConverter]
        public Color Color { get; set; }

        [PetaPoco.Column]
        [PetaPoco.ImageValueConverter]
        public Image Icon { get; set; }

        public static List<ItemReason> Load()
        {
            using (PetaPoco.Database db = new PetaPoco.Database())
            {
                // Modify PetaPoco.ConventionMapper for using ValueConverterAttribute (use IoC container in real project)
                ((PetaPoco.ConventionMapper)db.DefaultMapper).FromDbConverter = (pi, t) =>
               {
                   var valueConverter = pi.GetCustomAttributes(typeof(ValueConverterAttribute), true).FirstOrDefault() as ValueConverterAttribute;
                   if (valueConverter != null)
                       return valueConverter.ConvertFromDb;
                   return null;
               };
                ((PetaPoco.ConventionMapper)db.DefaultMapper).ToDbConverter = (pi) =>
               {
                   var valueConverter = pi.GetCustomAttributes(typeof(ValueConverterAttribute), true).FirstOrDefault() as ValueConverterAttribute;
                   if (valueConverter != null)
                       return valueConverter.ConvertToDb;
                   return null;
               };

                return db.Fetch<ItemReason>(String.Empty);
            }
        }
    }
}