//PropertyGrid pg;
//pg.SelectedObject = new Car();
public class HeightConvert : TypeConvert
{
  public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
  {
     //...
  }
  public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
  {
     //...
  }
}
public class Car
{
    [TypeConvert(typeof(HeightConvert))]
    public int Height{get;set;}
}

    public class Tx
    {
        int val = 0;
        public int Value
        {
            get
            {
                return val;
            }
            set
            {
                if (value >= 0 && value <= 100)
                {
                    val = value;
                }
                else
                {
                    throw new Exception("数值有效范围为[0,100]");
                }
            }
        }
    }