Restrictor.cs

//General usage
[PXDBInt]
[PXSelector(typeof(Search<FAClass.assetID, Where<FAClass.recordType, Equal<FARecordType.classType>>>),
    typeof(FAClass.assetCD), typeof(FAClass.assetTypeID), typeof(FAClass.description), typeof(FAClass.usefulLife),
    SubstituteKey = typeof(FAClass.assetCD),
    DescriptionField = typeof(FAClass.description), CacheGlobal = true)]
[PXRestrictor(typeof(Where<FAClass.active, Equal<True>>), Messages.InactiveFAClass, typeof(FAClass.assetCD))]
[PXUIField(DisplayName = "Asset Class", Visibility = PXUIVisibility.Visible)]
public virtual int? ClassID { get; set; }

//Several restrictors
[PXDefault]
[ContractTemplate(Required = true)]
[PXRestrictor(typeof(Where<ContractTemplate.status, Equal<Contract.status.active>>), Messages.TemplateIsNotActivated, typeof(ContractTemplate.contractCD))]
[PXRestrictor(typeof(Where<ContractTemplate.effectiveFrom, LessEqual<Current<AccessInfo.businessDate>>, 
    Or<ContractTemplate.effectiveFrom, IsNull>>), Messages.TemplateIsNotStarted)]
[PXRestrictor(typeof(Where<ContractTemplate.discontinueAfter, GreaterEqual<Current<AccessInfo.businessDate>>, 
    Or<ContractTemplate.discontinueAfter, IsNull>>), Messages.TemplateIsExpired)]
public virtual int? TemplateID { get; set;}

//One more example
[PXDBString(5, IsFixed = true, IsUnicode = false)]
[PXUIField(DisplayName = "Type", Required = true)]
[PXSelector(typeof(EPActivityType.type), DescriptionField = typeof(EPActivityType.description))]
[PXRestrictor(typeof(Where<EPActivityType.active, Equal<True>>), Messages.InactiveActivityType, typeof(EPActivityType.type))]
[PXRestrictor(typeof(Where<EPActivityType.isInternal, Equal<True>>), Messages.ExternalActivityType, typeof(EPActivityType.type))]
public virtual string Type { get; set; }