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

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"); 
        } 
    } 
} 
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

<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

this.DataContext = new DataValidationViewModel(); 
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

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