private void maskedTextBox1_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
     double val  =0;
     double.TryParse(maskedTextBox1.Text, out val);
     if(val <=4)
         student.GPA = val;
 }

		private void maskedTextBox1_MaskInputRejected(object sender,
  MaskInputRejectedEventArgs e)
		{
			Control control = (Control)sender;
			// Show an error notification.
			toolTip1.Show("That character is not allowed in this text box.",
				  control, new Point(control.Height, control.Height + 1));
		}

        internal static string GetMaskInputRejectedErrorMessage(MaskInputRejectedEventArgs e)
        {
            string str;
            switch (e.RejectionHint)
            {
                case MaskedTextResultHint.PositionOutOfRange:
                    str = System.Design.SR.GetString("MaskedTextBoxHintPositionOutOfRange");
                    break;

                case MaskedTextResultHint.NonEditPosition:
                    str = System.Design.SR.GetString("MaskedTextBoxHintNonEditPosition");
                    break;

                case MaskedTextResultHint.UnavailableEditPosition:
                    str = System.Design.SR.GetString("MaskedTextBoxHintUnavailableEditPosition");
                    break;

                case MaskedTextResultHint.PromptCharNotAllowed:
                    str = System.Design.SR.GetString("MaskedTextBoxHintPromptCharNotAllowed");
                    break;

                case MaskedTextResultHint.SignedDigitExpected:
                    str = System.Design.SR.GetString("MaskedTextBoxHintSignedDigitExpected");
                    break;

                case MaskedTextResultHint.LetterExpected:
                    str = System.Design.SR.GetString("MaskedTextBoxHintLetterExpected");
                    break;

                case MaskedTextResultHint.DigitExpected:
                    str = System.Design.SR.GetString("MaskedTextBoxHintDigitExpected");
                    break;

                case MaskedTextResultHint.AlphanumericCharacterExpected:
                    str = System.Design.SR.GetString("MaskedTextBoxHintAlphanumericCharacterExpected");
                    break;

                case MaskedTextResultHint.AsciiCharacterExpected:
                    str = System.Design.SR.GetString("MaskedTextBoxHintAsciiCharacterExpected");
                    break;

                default:
                    str = System.Design.SR.GetString("MaskedTextBoxHintInvalidInput");
                    break;
            }
            return string.Format(CultureInfo.CurrentCulture, System.Design.SR.GetString("MaskedTextBoxTextEditorErrorFormatString"), new object[] { e.Position, str });
        }

 void maskedTextBox1_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
     if (maskedTextBox1.MaskFull)
     {
         toolTip1.ToolTipTitle = "Input Rejected - Too Much Data";
         toolTip1.Show("You cannot enter any more data into the date field. Delete some characters in order to insert more data.", maskedTextBox1, 0, -20, 5000);
     }
     else if (e.Position == maskedTextBox1.Mask.Length)
     {
         toolTip1.ToolTipTitle = "Input Rejected - End of Field";
         toolTip1.Show("You cannot add extra characters to the end of this date field.", maskedTextBox1, 0, -20, 5000);
     }
     else
     {
         toolTip1.ToolTipTitle = "Input Rejected";
         toolTip1.Show("You can only add numeric characters (0-9) into this date field.", maskedTextBox1, 0, -20, 5000);
     }
 }

 private void txtStartTime_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
     if (txtStartTime.MaskFull)
     {
         toolTip.ToolTipTitle = "Invalid Time";
         toolTip.Show("You cannot enter any more data into the time field.", txtStartTime, 0, -20, 5000);
     } else if (e.Position == txtStartTime.Mask.Length)
     {
         toolTip.ToolTipTitle = "Invalid Time";
         toolTip.Show("You cannot add extra number to the end of this time.", txtStartTime, 0, -20, 5000);
     } else
     {
         toolTip.ToolTipTitle = "Invalid Time";
         toolTip.Show("You can only add numeric characters (0-9) into this time field.", txtStartTime, 0, -20, 5000);
     }
     btnOk.Enabled = false;
 }

 private void ser_op_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
 }

 /// <summary>
 /// Raises the MaskInputRejected event.
 /// </summary>
 /// <param name="e">An MaskInputRejectedEventArgs that contains the event data.</param>
 protected virtual void OnMaskInputRejected(MaskInputRejectedEventArgs e)
 {
     if (MaskInputRejected != null)
         MaskInputRejected(this, e);
 }

 private void textCantHuespedes_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
     showToolTip("Ingrese solamente números.", textCantHuespedes, textCantHuespedes.Location);
 }

 private void txtPassword_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
 }

 private void maskedTextBox_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
     this.errorProvider.SetError(this.cloneMtb, MaskedTextBoxDesigner.GetMaskInputRejectedErrorMessage(e));
 }

        private void UserName_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
        {

        }

 private void masktxtbTel_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
 }

 private void maskedTextBox2_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
     toolTip2.ToolTipTitle = "Invalid Input";
     toolTip2.Show("Invalid Sensitivity", maskedTextBox2, maskedTextBox2.Location, 5000);
 }

 //shows a tooltip if the users ID contains invalid characters or is too long
 private void maskedTextBox1_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
     toolTip1.ToolTipTitle = "Invalid Input";
     toolTip1.Show("Invalid UserID", maskedTextBox1, maskedTextBox1.Location, 5000);
 }

 private void textEstadia_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
     showToolTip("Ingrese solamente números.", textEstadia, textEstadia.Location);
 }

 private void maskedTextBox1_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
     //envia los datos al la capa negocios
 }

 private void maskedTextBox3_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
     cnempleado.CelEmpleadoG = maskedTextBox3.Text;  //envia los datos al la capa negocios
 }

 private void class_subject_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
 }

 private void tbBirthday_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
 }

 private void txtBranchID_MaskInputRejected(object sender, MaskInputRejectedEventArgs e)
 {
 }