小生刚开始学习C#，做了个简单程序题，请问我想根据textbox输入的内容，点击按键查询，从已有的SQL数据中，筛选信息，代码我都写了，为什么不能改变呢，请前辈指点，谢谢



            string str1 =textBox1.Text;
            string str2 =textBox2.Text;
            string connnectionString = Properties.Settings.Default.Database1ConnectionString;
            SqlConnection conn = new SqlConnection(connnectionString);
            conn.Open();
            SqlCommand cmd = new SqlCommand("select * from GoodsTable2 where 供货日期='"+str1+"' or 供货商='"+str2+"' ", conn);