private void button_ask_Click(object sender, EventArgs e) { string curr1 = textBox_curr1.Text; string curr2 = textBox_curr2.Text; if (curr1 == string.Empty || curr2 == string.Empty) { MessageBox.Show("Enter curr1 and curr2 pls!"); return; } string answ = _client.AskServer(curr1, curr2); textBox_answer.Text += answ + "\r\n"; }