private void emailTextBox_Leave(object sender, EventArgs e)
 {
     emailTextBox.Enabled = false;
     if (String.Equals(emailTextBox.Text, email) == false)
     {
         datachange = true;
         if (ValidationCheck.CheckEmail(emailTextBox.Text))
         {
             emailExist.Visible = true;
             button1.Enabled    = false;
         }
         else
         {
             emailExist.Visible = false;
             button1.Enabled    = true;
         }
     }
 }