Throwing Validation Exceptions

Masks do not necessarily guarantee that a user's input will represent a valid value for a given type; for example, -9 could be entered for an age in years. You can verify that a user's input represents a valid value by using Data Validation. The RadMaskedInput controls provides out-of-the-box support for Data Validation. Data validation, being one of the major points when building line-of-business applications, can help you to easily separate the validation logic from the application's UI.

This topic will show you how to use RadMaskedInput controls to distinguish between proper and improper user input.

For the purpose of this tutorial you need to create a new class named DataValidationViewModel. It will take care of the validation rules.

Example 1: Custom validation class

C#

	public class DataValidationViewModel : ViewModelBase
	{
		private double doubleValue;
		private string stringValue;
		private decimal decimalValue;
		private DateTime dateTimeValue;
		[Range(-100d, 100d)]
		public double DoubleValue
		{
			get { return doubleValue; }
			set
			{
				doubleValue = value;
				this.OnPropertyChanged("DoubleValue");
			}
		}
		[Range(typeof(decimal), "-100", "100")]
		public decimal DecimalValue
		{
			get { return decimalValue; }
			set
			{
				decimalValue = value;
				this.OnPropertyChanged("DecimalValue");
			}
		}
		[Range(typeof(DateTime), "01.01.1900", "01.01.2099")]
		public DateTime DateTimeValue
		{
			get { return dateTimeValue; }
			set
			{
				dateTimeValue = value;
				this.OnPropertyChanged("DateTimeValue");
			}
		}
		[StringLength(6)]
		[Required()]
		public string StringValue
		{
			get { return stringValue; }
			set
			{
				stringValue = value;
				this.OnPropertyChanged("StringValue");
			}
		}
	}

VB.NET

	Public Class DataValidationViewModel
		Inherits ViewModelBase
		Private m_doubleValue As Double
		Private m_stringValue As String
		Private m_decimalValue As Decimal
		Private m_dateTimeValue As Date
		Public Property DoubleValue() As Double
			Get
				Return m_doubleValue
			End Get
			Set
				If Value < -100 OrElse Value > 100 Then
					Throw New ValidationException([String].Format("Value is {0} than {1}.", (If(Value > 100, "greater", "less")), Value))
				End If
				m_doubleValue = Value
				Me.OnPropertyChanged("DoubleValue")
			End Set
		End Property
		Public Property DecimalValue() As Decimal
			Get
				Return m_decimalValue
			End Get
			Set
				If Value < -100 OrElse Value > 100 Then
					Throw New ValidationException([String].Format("Value is {0} than {1}.", (If(Value > 100, "greater", "less")), Value))
				End If
				m_decimalValue = Value
				Me.OnPropertyChanged("DecimalValue")
			End Set
		End Property
		Public Property DateTimeValue() As Date
			Get
				Return m_dateTimeValue
			End Get
			Set
				If Value < Date.Parse("01.01.1900") OrElse Value > Date.Parse("01.01.2099") Then
					Throw New ValidationException([String].Format("Value is {0} than {1}.", (If(Value > Date.Parse("01.01.2099"), "greater", "less")), Value))
				End If
				m_dateTimeValue = Value
				Me.OnPropertyChanged("DateTimeValue")
			End Set
		End Property
		Public Property StringValue() As String
			Get
				Return m_stringValue
			End Get
			Set
				If Value.Length > 6 Then
					Throw New ValidationException([String].Format("Value's length is greater than {0}.", Value.Length))
				End If
				m_stringValue = Value
				Me.OnPropertyChanged("StringValue")
			End Set
		End Property
	End Class

Declare several RadMaskedInput controls in XAML for displaying the sample data. Pay attention on the following things:

• The RadMaskedInput controls' Value property is data bound to the corresponding property in the ViewModel.

• The ValidatesOnExceptions and NotifyOnValidationError properties of the data binding are set to True.

Example 2: Defining several RadMaskedInput controls in XAML

XAML

	<StackPanel x:Name="LayoutRoot" Background="White">
	    <telerik:RadMaskedNumericInput Width="200"
	                                    Margin="10, 10, 10, 0"
	                                    ErrorMessage="{Binding Path=Text, ElementName=customErrorMessage}"
	                                    InputBehavior="Insert"
	                                    Value="{Binding Path=DoubleValue, Mode=TwoWay, NotifyOnValidationError=True, ValidatesOnExceptions=True}" />
	    <telerik:RadMaskedCurrencyInput Width="200"
	                                    Margin="10, 10, 10, 0"
	                                    ErrorMessage="{Binding Path=Text, ElementName=customErrorMessage}"
	                                    InputBehavior="Insert"
	                                    Value="{Binding Path=DecimalValue, Mode=TwoWay, NotifyOnValidationError=True, ValidatesOnExceptions=True}" />
	    <telerik:RadMaskedDateTimeInput Width="200"
	                                    Margin="10, 10, 10, 0"
	                                    ErrorMessage="{Binding Path=Text, ElementName=customErrorMessage}"
	                                    Value="{Binding Path=DateTimeValue, Mode=TwoWay, NotifyOnValidationError=True, ValidatesOnExceptions=True}" />
	    <telerik:RadMaskedTextInput Width="200"
	                                Margin="10"
	                                ErrorMessage="{Binding Path=Text, ElementName=customErrorMessage}"
	                                Value="{Binding Path=StringValue, Mode=TwoWay, NotifyOnValidationError=True, ValidatesOnExceptions=True}" />
	</StackPanel>

Finally, set the DataValidationViewModel to the UserControl's DataContext property.

Example 3: Setting the DataContext to DataValidationViewModel

C#

	this.DataContext = new DataValidationViewModel();

VB.NET

	Me.DataContext = New DataValidationViewModel()

Run the demo and fill all fields with valid data. As you can see no validation errors occur.

Next try to fill some improper data.

See Also

• Getting Started
• Common Features