นำค่าจาก textbox ไปเปรียบเทียบ database เขียนยังไงคับ

<asp:Label ID="Label1" runat="server" Text="Label">salary</asp:Label>
   <asp:TextBox  ID="TextBox1" runat="server"></asp:TextBox>
   <asp:Button ID="submit" runat="server" Text="submit" OnClick="submit_Click" />


    Point is : <asp:Label ID="Label2" runat="server" Text="Label"></asp:Label>

 protected void submit_Click(object sender, EventArgs e)
        {
            //Dummy list replaced get data from db
            List<Employee> employeeList = new List<Employee>();
            employeeList.Add(new Employee { Id = 1, Salary = 15, Point = 3 });
            employeeList.Add(new Employee { Id = 2, Salary = 20, Point = 2 });
            employeeList.Add(new Employee { Id = 3, Salary = 25, Point = 1 });

            int inputValue = int.Parse(TextBox1.Text);
            //Find object which salary >= input and get point in this object
            var employee = employeeList.Where(a => a.Salary >= inputValue).OrderBy(x=>x.Salary).FirstOrDefault();
            if (employee != null)
                Label2.Text = employee.Point.ToString();
            else
                Label2.Text = employeeList.Min(a => a.Point).ToString();
        }

		SqlConnection objConn = new SqlConnection();
		SqlCommand objCmd = new SqlCommand();
		SqlDataAdapter dtAdapter = new SqlDataAdapter();
       
		DataSet ds = new DataSet();
		DataTable dt;
		String strConnString,strSQL;


		strConnString = "Server=localhost;UID=sa;PASSWORD=;database=mydatabase;Max Pool Size=400;Connect Timeout=600;";
		String strInput = "22";
		strSQL = "SELECT TOP 1 * FROM table_name WHERE salary <= '" & strInput & "' ORDER BY salary ASC";

		objConn.ConnectionString = strConnString;

		objCmd.Connection = objConn;
		objCmd.CommandText = strSQL;
		objCmd.CommandType = CommandType.Text;

		dtAdapter.SelectCommand = objCmd;

		dtAdapter.Fill(ds);
		dt = ds.Tables[0];

		dtAdapter = null;
		objConn.Close();
		objConn = null;

		// Use
		this.txtBoxNew.Text = dt.Rows[0]["point"].ToString();