RuleFromBoolPropertyAttribute Class

Defines a validation rule that demands a true value for the target public non-persistent Boolean property.

Namespace: DevExpress.Persistent.Validation

Assembly: DevExpress.Persistent.Base.v18.2.dll

Declaration

C#

[AttributeUsage(AttributeTargets.Property, AllowMultiple = true)]
public class RuleFromBoolPropertyAttribute :
    RuleBaseAttribute,
    IRuleFromBoolPropertyProperties,
    IRulePropertyValueProperties,
    IRuleCollectionPropertyProperties,
    IRuleBaseProperties

VB.NET

<AttributeUsage(AttributeTargets.Property, AllowMultiple:=True)>
Public Class RuleFromBoolPropertyAttribute
    Inherits RuleBaseAttribute
    Implements IRuleFromBoolPropertyProperties,
               IRulePropertyValueProperties,
               IRuleCollectionPropertyProperties,
               IRuleBaseProperties

Remarks

Apply this attribute to a business class’ Boolean public non-persistent property to define a rule that will be satisfied when this property returns true. This rule is not intended for checking the target property’s data, and therefore, this property should be non-persistent. Implement a complex check in this property, and apply the RuleFromBoolPropertyAttribute to it. Use this approach (a non-persistent Boolean property plus the RuleFromBoolPropertyAttribute) when none of the remaining built-in validation rules suit your needs. To provide details on the rule, use the common parameters that are inherited from the RuleBaseAttribute class.

The rule generated by the RuleFromBoolPropertyAttribute will be loaded to the Application Model‘s IModelValidationRules node. So, you can customize this rule via the Model Editor. For details, refer to the Implement Property Value Validation in the Application Model topic.

Note

The property to which the RuleFromBoolProperty attribute is applied must be public. If it is necessary to hide the property from the UI, decorate it with the Browsable(false) attribute. This may also improve the performance, because the property getter will be invoked only when required.

The following code demonstrates how to use the RuleFromBoolPropertyAttribute. The IsEmailUnique property checks whether the current Contact object’s Email is not set for other Contact objects. The rule generated from the attribute is checked when committing a Contact object to the database. When the IsEmailUnique property returns false, an error message with the provided details is invoked.

C#

using DevExpress.Data.Filtering;
using DevExpress.Persistent.BaseImpl;
using DevExpress.Persistent.Validation;
using DevExpress.Xpo;
// ...
public class Contact: BaseObject {
   //... 
   private string email;
   public string Email {
       get { return email; }
       set { SetPropertyValue("Email", ref email, value); }
   }
   [Browsable(false)]
   [RuleFromBoolProperty("ContactUniqueEmail", DefaultContexts.Save, 
      "Contact with this Email already exists")]
   public bool IsEmailUnique {
      get {
         string toLowerEmail = Object.ReferenceEquals(Email, null) ? String.Empty : Email.ToLower();
         XPCollection<Contact> contacts = 
               new XPCollection<Contact>(PersistentCriteriaEvaluationBehavior.InTransaction,
               Session, new BinaryOperator(new FunctionOperator(FunctionOperatorType.Lower, 
               new OperandProperty("Email")),
            new OperandValue(toLowerEmail), BinaryOperatorType.Equal));
         foreach (Contact contact in contacts) {
            if (contact != this) {
               return false;
            }
         }
         return true;
      }
   }
}

VB.NET

Imports DevExpress.Data.Filtering
Imports DevExpress.Persistent.BaseImpl
Imports DevExpress.Persistent.Validation
Imports DevExpress.Xpo
' ...
Public Class Contact
    Inherits BaseObject

   '... 
   Private _email As String
   Public Property Email() As String
       Get
           Return _email
       End Get
       Set(ByVal value As String)
           SetPropertyValue("Email", _email, value)
       End Set
   End Property
   <Browsable(False), _
   RuleFromBoolProperty("ContactUniqueEmail", DefaultContexts.Save, "Contact with this Email already exists")> _
   Public ReadOnly Property IsEmailUnique() As Boolean
      Get
         Dim toLowerEmail As String = If(Object.ReferenceEquals(Email, Nothing), String.Empty, Email.ToLower())
         Dim contacts As New XPCollection(Of Contact)( _
         PersistentCriteriaEvaluationBehavior.InTransaction, Session, _
         New BinaryOperator(New FunctionOperator(FunctionOperatorType.Lower, New OperandProperty("Email")), _
         New OperandValue(toLowerEmail), BinaryOperatorType.Equal))
         For Each contact As Contact In contacts
            If contact IsNot Me Then
               Return False
            End If
         Next contact
         Return True
      End Get
   End Property
End Class

You can highlight the property that should be corrected for the current object’s validity. In the instance above, you can highlight the Email property as an invalid property. To highlight the required properties, pass their names as the RuleFromBoolPropertyAttribute.UsedProperties parameter (use a comma to separate multiple property names).

C#

[RuleFromBoolProperty("ContactUniqueEmail", DefaultContexts.Save, 
  "Contact with this Email already exists", UsedProperties = "Email")]
public bool IsEmailUnique {
      //...
}

VB.NET

<RuleFromBoolProperty("ContactUniqueEmail", DefaultContexts.Save, _
    "Contact with this Email already exists", UsedProperties := "Email"),> _
Public ReadOnly Property IsEmailUnique() As Boolean
    '...
EndProperty

You can see examples of the RuleFromBoolProperty and other validation attributes in the Validation section of the FeatureCenter demo. This demo is located in the %PUBLIC%\Documents\DevExpress Demos 18.2\Components\eXpressApp Framework\FeatureCenter folder, by default.

Implements

IRuleCollectionPropertyProperties

IRuleBaseProperties

Inheritance

Object

Attribute

RuleBaseAttribute

RuleFromBoolPropertyAttribute