Color Properties in XPO

• Mar 06, 2024
• 2 minutes to read

This topic demonstrates two approaches to store a System.Drawing.Color property value in the database managed by the eXpressPersistent Objects ORM.

1. The first approach is to implement a Value Converter.

   using System;
   using System.Drawing;
   using DevExpress.Xpo.Metadata;
   // ...
   public class ColorValueConverter : ValueConverter {
       public override object ConvertFromStorageType(object obj) {
           if(obj == null) {
               return null;
           }
           return Color.FromArgb((Int32)obj);
       }
       public override object ConvertToStorageType(object obj) {
           if(obj == null) {
               return null;
           }
           return ((Color)obj).ToArgb();
       }
       public override Type StorageType {
           get { return typeof(Int32); }
       }
   }
   

   After that, decorate properties that need to be converted with the ValueConverterAttribute and the converter will be called on each attempt to store or acquire a value of the Color type.

   using DevExpress.Xpo;
   using System.Drawing;
   //...
   private Color color;
   [ValueConverter(typeof(ColorValueConverter))]
   public Color Color {
       get { return color; }
       set { SetPropertyValue(nameof(Color), ref color, value); }
   }
   

2. Another approach is to convert the Color type to Int32 on property implementation using get and set accessors, as shown below.

   using DevExpress.Xpo;
   using System.Drawing;
   //...
   [Persistent("Color")]
   private Int32 color;
   [NonPersistent]
   public Color Color {
       get { return Color.FromArgb(color); }
       set {
           color = value.ToArgb();
           OnChanged(nameof(Color));
       }
   }
   

   Note

   If the type’s class does not have an appropriate conversion method (Color.ToArgb in this case), implement a Type Converter and use it any time you need a value conversion between the type you need to store and an ORM-friendly type.