private void button18_Click(object sender, EventArgs e) {//'=' if (leBrac == true || biOpe == true || lastStr.Count == 0) { } else { int n_left = 0, n_right = 0; //已经输入的左右括号个数 foreach (String i in lastStr) { if (i == ",(,") { n_left++; } if (i == ",),") { n_right++; } } if (n_left != n_right) { } //左右括号数不配对则不能开始计算 else { Calculate calculate = new Calculate(); Pair answer = calculate.Run(lastStr); if (answer.flag == false) { textBox1.Text = "Error"; } else { textBox2.Text = textBox1.Text; textBox1.Text = Convert.ToString(answer.answer); } SetBool(); lastStr.Clear(); haveDot = false; beginning = true; } } }