此示例所示的 RuleRequiredFieldPersistent 類是一個普通的業務類。類實現 IRuleSource 介面，並用於創建和存儲在資料庫中的 RuleRequiredField 驗證規則。在 CreateRules 方法中實例化一個 RuleRequiredField 驗證規則，基於 RuleRequiredFieldPersistent 類的公共屬性的值。RuleRequiredFieldPersistent 類標記 DefaultClassOptionsAttribute，以便最終用戶可以手動創建驗證規則通過相應的列表視圖。

[DefaultClassOptions]
public class RuleRequiredFieldPersistent : BaseObject, 
    DevExpress.Persistent.Validation.IRuleSource {
    public RuleRequiredFieldPersistent(Session session) : base(session) { }
    public string RuleName {
        get { return GetPropertyValue<string>("RuleName"); }
        set { SetPropertyValue("RuleName", value); }
    }
    public string CustomMessageTemplate {
        get { return GetPropertyValue<string>("CustomMessageTemplate"); }
        set { SetPropertyValue("CustomMessageTemplate", value); }
    }
    public bool SkipNullOrEmptyValues {
        get { return GetPropertyValue<bool>("SkipNullOrEmptyValues"); }
        set { SetPropertyValue("SkipNullOrEmptyValues", value); }
    }
    public string Id {
        get { return GetPropertyValue<string>("Id"); }
        set { SetPropertyValue("Id", value); }
    }
    public bool InvertResult {
        get { return GetPropertyValue<bool>("InvertResult"); }
        set { SetPropertyValue("InvertResult", value); }
    }
    public string ContextIDs {
        get { return GetPropertyValue<string>("ContextIDs"); }
        set { SetPropertyValue("ContextIDs", value); }
    }
    public string Property {
        get { return GetPropertyValue<string>("Property"); }
        set { SetPropertyValue("Property", value); }
    }
    [Persistent("ObjectType")]
    protected string ObjectType {
        get {
            if(ObjectTypeCore != null) {
                return ObjectTypeCore.FullName;
            }
            return "";
        }
        set { ObjectTypeCore = ReflectionHelper.FindType(value); }
    }
    [NonPersistent]
    [TypeConverter(typeof(DevExpress.Persistent.Base.LocalizedClassInfoTypeConverter))]
    public Type ObjectTypeCore {
        get { return GetPropertyValue<Type>("ObjectTypeCore"); }
        set { SetPropertyValue("ObjectTypeCore", value); }
    }
    #region IRuleSource Members
    public System.Collections.Generic.ICollection<IRule> CreateRules() {
        System.Collections.Generic.List<IRule> list = new System.Collections.Generic.List<IRule>();
        RuleRequiredField rule = new RuleRequiredField();
        rule.Properties.SkipNullOrEmptyValues = this.SkipNullOrEmptyValues;
        rule.Properties.Id = this.Id;
        rule.Properties.InvertResult = this.InvertResult;
        rule.Properties.CustomMessageTemplate = this.CustomMessageTemplate;
        rule.Properties.TargetContextIDs = new ContextIdentifiers(this.ContextIDs);
        rule.Properties.TargetType = this.ObjectTypeCore;
        if(rule.Properties.TargetType != null) {
            foreach(PropertyInfo pi in rule.Properties.TargetType.GetProperties()) {
                if(pi.Name == this.Property) {
                    rule.Properties.TargetPropertyName = pi.Name;
                }
            }
        }
        for(int i = Validator.RuleSet.RegisteredRules.Count - 1; i >= 0; i--) {
            if(Validator.RuleSet.RegisteredRules[i].Id == this.Id) {
                Validator.RuleSet.RegisteredRules.RemoveAt(i);
            }
        }
        list.Add(rule);
        return list;
    }
    [Browsable(false)]
    public string Name {
        get { return this.RuleName; }
    }
    #endregion
}

可以看到，這個示例中，只返回了一個規則，而在實際項目中，可以使用BO定義一個子集合，集合中定義N種規則。

不要定義N個BO並都實現　IRuleSource 那樣有點浪費。