private void button1_Click(object sender, EventArgs e) {
         if(textBox1.Text == String.Empty || textBox2.Text == String.Empty) {
            MessageBox.Show("Please, fill all fields");
            return;
         }
         try {
            using(var objProvider = new MailProvider()) {
               Group objReceiverGroup = objProvider.GetGroupById(iNodeId);
               if(objReceiverGroup == null) {
                  throw new ArgumentException("Cant find group with current ID: " + iNodeId);
               }

               var objReciever = new Receiver();
               objReciever.Name = textBox1.Text;
               objReciever.Email = textBox2.Text;
               objReciever.Group = objReceiverGroup;

               objProvider.AddReceiver(objReciever);
            }
            this.Close();
         }
         catch(Exception ex) {
            MessageBox.Show(ex.Message);
         }
      }