Attaching a Virtual Branch to the Logical Tree in WPF

using System;
using System.Globalization;
using System.Windows;
using System.Windows.Controls;

namespace ValidationRuleWithBoundProperty
{
	/// <summary>
	/// Ensures that the validated value is a multiple of a specified number.
	/// </summary>
	public class IsMultipleOfValidationRule : ValidationRule
	{
		private IntegerContainer divisorContainer;

		public IntegerContainer DivisorContainer
		{
			get { return divisorContainer; }
			set { divisorContainer = value; }
		}

		public override ValidationResult Validate( object value, CultureInfo cultureInfo )
		{
			try
			{
				int dividend = (int)Convert.ChangeType( value, typeof( int ) );

				int divisor = this.DivisorContainer.Value;

				if( dividend % divisor == 0 )
					return ValidationResult.ValidResult;

				return new ValidationResult(
					false,
					"The number is not a multiple of " + divisor );
			}
			catch
			{
				return new ValidationResult( false, "Not a number." );
			}
		}
	}
}