How to: Validate an Object

• Oct 29, 2020

This example demonstrates how to prevent the Name property from being set to an empty string. If this property is set to an empty string, XPO throws a RequiredPropertyValueMissing exception.

C#

public class RequiredPropertyValueMissing: Exception {
    public RequiredPropertyValueMissing(XPObject theObject, string propertyName):
        base(String.Format("The {0} property of the {1} object with id {2} must have a value", 
          propertyName, theObject.GetType().Name, theObject.Oid)) {
    }
}

public class Company : Person {
public string Name {
    get { return fName; }
    set { SetPropertyValue(nameof(Name), ref fName, value); }
}
string fName = "";

    protected override void OnSaving() {
        if (Name == "")
          throw new RequiredPropertyValueMissing(this, nameof(Name));
    }
}

VB.NET

Public Class RequiredPropertyValueMissing : Inherits Exception
    Public Sub New(ByVal theObject As XPObject, ByVal propertyName As String)
    MyBase.New(String.Format("The {0} property of the {1} object with id {2} must have a value", _
          propertyName, theObject.GetType().Name, theObject.Oid))
    End Sub
End Class

Public Class Company : Inherits Person
    Public Property Name() As String
        Get
            Return fName
        End Get
        Set(ByVal value as String)
            SetPropertyValue(NameOf(Name), fName, value)
        End Set
    End Property
    Private fName As String = ""

    Protected Overrides Sub OnSaving()
        If (Name = "") Then
            Throw New RequiredPropertyValueMissing(This, NameOf(Name))
        End If
    End Sub
End Class