Validation in UWP Masked TextBox (SfMaskedEdit)

18 Feb 20253 minutes to read

Input validation happens based on the value of the ValidationMode property. The enum values of this property are

• LostFocus
• KeyPress
• HasError

KeyPress

When the ValidationMode is KeyPress, the validation is raised for each key press.

LostFocus

When the ValidationMode is LostFocus, the validation takes place when the control lost its focus

HasError

This read only property is used to check whether the validation succeeds or not. It returns true once validation succeeds or else set to false. The following code example shows the usage of HasError property.

XAML

<Input:SfMaskedEdit x:Name="sfMaskedEdit" MaskType="Simple" Mask="00/00/0000" Value="14/11/2014" ValidationMode="LostFocus" LostFocus="sfMaskedEdit_LostFocus"/>

C#

private void sfMaskedEdit_LostFocus(object sender, RoutedEventArgs e)
{
    if (sfMaskedEdit.HasError)
    {
        MessageBox.Show("Please enter the correct date");
    }
}

Custom Validation

In SfMaskedEdit control there is no event for the validation. The custom validation based on the ValidationMode property of SfMaskedEdit using attached properties of Validation class. Also HasError property has been used for Validation in source level.

Custom validation can be implemented as follows

Step 1. Create a class inherited from ValidationRule.

Step 2. Override ValidationResult property and implement custom validation logic.

For Example:

C#

public class NameValidator : ValidationRule
{
    public override ValidationResult Validate
	(object value, System.Globalization.CultureInfo cultureInfo)
        {

        	if (value == null)
                return new ValidationResult(false, "value cannot be empty.");
            else
            	{
                    if (value.ToString() == "__/__/____" || value.ToString().Contains("_")) 
                    	return new ValidationResult(false, "Name cannot be more than 8 characters long.");
            	}
            return ValidationResult.ValidResult;
        }
}

XAML

Step3. Set Triggers for KeyPress and LostFocus ValidationMode

		<Trigger Property="ValidationMode" Value="KeyPress">
            <Setter Property="Text">
                <Setter.Value>
                    Binding Path="Value" Mode="TwoWay" UpdateSourceTrigger="PropertyChanged">
                        <Binding.ValidationRules>
                             <local:NameValidator/>
                        </Binding.ValidationRules>
                    </Binding>
                </Setter.Value>
            </Setter>
        </Trigger>