public partial class RequiredFieldValidator : Component
    {
        Private Fields#region Private Fields

        private Control controlToValidate = null;
        private string errorMessage = string.Empty;
        private string initialValue = string.Empty;
        private bool isValid = true;
        private Icon icon = new Icon(typeof(ErrorProvider), "Error.ico");
        private ErrorProvider errorProvider = new ErrorProvider();

        #endregion

        Constructors#region Constructors

        public RequiredFieldValidator()
        {
            InitializeComponent();
        }

        public RequiredFieldValidator(IContainer container)
        {
            container.Add(this);

            InitializeComponent();
        }

        #endregion

        Public Properties#region Public Properties

        [Category("Behaviour")]
        [Description("Get or sets the control to validate.")]
        [DefaultValue(null)]
        [TypeConverter(typeof(ValidatableControlConverter))]
        public Control ControlToValidate
        {
            get
            {
                return controlToValidate;
            }
            set
            {
                controlToValidate = value;
                if ((controlToValidate != null) && (!DesignMode))
                {
                    controlToValidate.Validating += new CancelEventHandler(controlToValidate_Validating);
                }
            }
        }

        [Category("Appearance")]
        [Description("Gets or sets the text for the error message.")]
        [DefaultValue("")]
        public string ErrorMessage
        {
            get
            {
                return errorMessage;
            }
            set
            {
                errorMessage = value;
            }
        }

        [Category("Appearance")]
        [Description("Gets or sets the Icon to display error message.")]
        public Icon Icon
        {
            get
            {
                return icon;
            }
            set
            {
                icon = value;
            }
        }

        [Category("Behaviour")]
        [Description("Gets or sets the default value to validate against.")]
        [DefaultValue("")]
        public string InitialValue
        {
            get
            {
                return initialValue;
            }
            set
            {
                initialValue = value;
            }
        }

        [Browsable(false)]
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
        public bool IsValid
        {
            get
            {
                return isValid;
            }
            set
            {
                isValid = value;
            }
        }

        #endregion

        public void Validate()
        {
            if (controlToValidate == null)
            {
                isValid = true;
                return;
            }

            string controlValue = controlToValidate.Text.Trim();
            string _initValue;
            if (initialValue == null)
            {
                _initValue = string.Empty;
            }
            else
            {
                _initValue = initialValue.Trim();
            }
            isValid = (controlValue != _initValue);

            if (isValid)
            {
                errorProvider.SetError(controlToValidate, string.Empty);
            }
            else
            {
                errorProvider.SetError(controlToValidate, errorMessage);
            }
        }

        private void controlToValidate_Validating(object sender, CancelEventArgs e)
        {
            Validate();
        }
    }