Validating Data Through Data Annotations

Aside from the property level validation, RadDataForm supports validation through data annotations. Validation is performed on any occasion when changes are committed - navigation, insertion of new items or when AutoCommit is set to True, for example. This feature is available for both auto-generated and customized fields and all of the System.ComponentModel.DataAnnotations validation attributes are supported.

In order to enable this kind of validation you first need to include the System.ComponentModel.DataAnnotations namespace:

Example 1: Including System.ComponentModel.DataAnnotations

C#

	using System.ComponentModel.DataAnnotations;

VB.NET

	Imports System.ComponentModel.DataAnnotations

Now, let's define a simple Employee class with validation attributes.

Example 2: Creating an Employee class with validation attributes

C#

	public class Employee
	{
	    [Required]
	    public string FirstName { get; set; }
	    [Required(ErrorMessage = "LastName is required")]
	    public string LastName { get; set; }
	    [Range(21, 70)]
	    public int Age { get; set; }
	    [RegularExpression("[a-z]#[0-9]*")]
	    public string EmployeeID { get; set; }
	}

VB.NET

	Public Class Employee
	    <Required()>
	    Public Property FirstName() As String
	        Get
	            Return m_FirstName
	        End Get
	        Set(value As String)
	            m_FirstName = value
	        End Set
	    End Property
	    Private m_FirstName As String
	    <Required(ErrorMessage:="LastName is required")>
	    Public Property LastName() As String
	        Get
	            Return m_LastName
	        End Get
	        Set(value As String)
	            m_LastName = value
	        End Set
	    End Property
	    Private m_LastName As String
	    <Range(21, 70)>
	    Public Property Age() As Integer
	        Get
	            Return m_Age
	        End Get
	        Set(value As Integer)
	            m_Age = value
	        End Set
	    End Property
	    Private m_Age As Integer
	    <RegularExpression("[a-z]#[0-9]*")>
	    Public Property EmployeeID() As String
	        Get
	            Return m_EmployeeID
	        End Get
	        Set(value As String)
	            m_EmployeeID = value
	        End Set
	    End Property
	    Private m_EmployeeID As String
	End Class

Figure 1 shows RadDataForm's state after validation has been performed.

Figure 1: RadDataForm after validation has been performed

As seen in the above figure, item level validation errors are not respected by the separate editors' validation features (i.e. no validation tooltip is shown for the TextBox). Such behavior is expected, as respective bindings never get notified about these errors.

In order to notify the UI that validation has failed, you will need to throw a ValidationException. Example 3 shows how to do so through the static ValidateProperty method of the Validator class.

Example 3: Set validation through data DataAnnotations

C#

	private string firstName;

        [Required]
        public string FirstName
        {
            get { return this.firstName; }
            set
            {
                if (value != this.firstName)
                {
                    ValidationContext validationContext = new ValidationContext(this, null, null);
                    validationContext.MemberName = "FirstName";
                    Validator.ValidateProperty(value, validationContext);
                    this.firstName = value;
                    this.OnPropertyChanged("FirstName");
                }
            }
        }

VB.NET

	Private _firstName As String

        <Required>
        Public Property FirstName() As String
            Get
                Return Me._firstName
            End Get
            Set(ByVal value As String)
                If value <> Me._firstName Then
                    Dim validationContext As New ValidationContext(Me, Nothing, Nothing)
                    validationContext.MemberName = "FirstName"
                    Validator.ValidateProperty(value, validationContext)
                    Me._firstName = value
                    Me.OnPropertyChanged("FirstName")
                End If
            End Set
        End Property

Please, have in mind that those errors are removed from the validation summary on the next committing operation, unlike the property level ones, which are removed on property change.