gistfile1.txt

public class RegionManager : IRegionManager
{
  public static readonly DependencyProperty RegionNameProperty = DependencyProperty.RegisterAttached(
      "RegionName",
      typeof(string),
      typeof(RegionManager),
    new PropertyMetadata(OnSetRegionNameCallback));

  public static void SetRegionName(DependencyObject regionTarget, string regionName)
  {
    regionTarget.SetValue(RegionNameProperty, regionName);
  }
  
  ...
}