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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.

[C#] Example 1: Custom validation class

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] Example 1: Custom validation class

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.

[XAML] Example 2: Defining several RadMaskedInput controls in 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.

[C#] Example 3: Setting the DataContext to DataValidationViewModel

this.DataContext = new DataValidationViewModel();

[VB.NET] Example 3: Setting the DataContext to DataValidationViewModel

Me.DataContext = New DataValidationViewModel()

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

Validation Tool TipWPF

Next try to fill some improper data.

Validation Tool TipWPF

See Also