C# 添加信息出错 求解···

提示 ：字符串'）'有未闭合的引号 没找出啊  添加按钮事件
try
            {
                SqlConnection thisConnection = new SqlConnection("server=localhost;uid=sa;pwd=sa;database=studentroom");
                thisConnection.Open();
                SqlCommand cmd = new SqlCommand("insert into droom (dno,dphone,dheader,dnumber) values('" + this.textBox1.Text + "','" + this.textBox2.Text + "','" + this.textBox3.Text + "'," + this.textBox4.Text + "')", thisConnection);
                SqlDataReader myreader = cmd.ExecuteReader();
                //this.Close();
                thisConnection.Close();
                MessageBox.Show("添加成功！", "提示");
            }
            catch (Exception err)
            {
                MessageBox.Show(err.Message); --------------------编程问答-------------------- this.Connection.Open();

使用ExecuteNonQuery()即可 --------------------编程问答-------------------- 还是有错啊 --------------------编程问答-------------------- thisConnection.Open();
  SqlCommand cmd = new SqlCommand("insert into droom (dno,dphone,dheader,dnumber) values('" + this.textBox1.Text + "','" + this.textBox2.Text + "','" + this.textBox3.Text + "'," + this.textBox4.Text + "')", thisConnection);
  SqlDataReader myreader = cmd.ExecuteReader();
  //this.Close();
  thisConnection.Close(); --------------------编程问答-------------------- 怎么不把提示错误的代码放出来看看的 --------------------编程问答-------------------- 不能插图啊 

补充：.NET技术 ,  .NET Framework