IEmptyCheckable.IsEmpty Property

Gets if the IEmptyCheckable value is considered to be empty when validating via the RuleRequiredFieldAttribute.

Namespace: DevExpress.Persistent.Validation

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

Declaration

C#

bool IsEmpty { get; }

VB.NET

ReadOnly Property IsEmpty As Boolean

Property Value

Type	Description
Boolean	true, when the value is empty; otherwise, false.

Remarks

Support the IEmptyCheckable interface and implement the IsEmpty method, when it is required to validate properties of your custom type via the RuleRequiredField attribute. Below is the snippet from the Business Class Library’s FileData class, illustrating the implementation of this property:

C#

public class FileData : BaseObject, IFileData, IEmptyCheckable {
    // ...
    public string FileName {
        get { return fileName; }
        set {
            SetPropertyValue<string>("FileName", ref fileName, value);
        }
    }
    // ...
    [NonPersistent, MemberDesignTimeVisibility(false)]
    public bool IsEmpty {
        get { return string.IsNullOrEmpty(FileName); }
    }
}

VB.NET

Public Class FileData
    Inherits BaseObject
    Implements IFileData, IEmptyCheckable
    ' ...
    Public Property FileName() As String
        Get
            Return fileName
        End Get
        Set(ByVal value As String)
            SetPropertyValue(Of String)("FileName", fileName, value)
        End Set
    End Property
    ' ...
    <NonPersistent, MemberDesignTimeVisibility(False)> _
    Public ReadOnly Property IsEmpty() As Boolean
        Get
            Return String.IsNullOrEmpty(FileName)
        End Get
    End Property
End Class

With the IEmptyCheckable interface supported, the property of the FileData type can be validated in the following manner:

C#

public class Resume : BaseObject {
     // ...
    [RuleRequiredField("RuleRequiredField for Resume.FileData", 
        DefaultContexts.Save, ,"The file must be specified"]
    public FileData File {
        // ...
    }
    // ...
}

VB.NET

Public Class [Resume]
    Inherits BaseObject
    ' ...
    <RuleRequiredField("RuleRequiredField for Resume.FileData", _
    DefaultContexts.Save,"The file must be specified")> _
    Public ReadOnly Property File() As FileData
        ' ...
    End Property
    ' ...
End Class