按下按钮时刷新会话状态

Question

我有一个按钮，当按下它时，会根据列表框选择查找值，如果它在表中找到记录，它会从列表框中获取该值并将其放入会话中，刷新页面，然后会话用作数据源，即。找到会话 = 会话的位置。 现在发生的情况是，如果我想进行两次连续搜索，该按钮不会存储新会话，而是使用旧会话。因此，如果我先搜索 x，然后搜索 y，它会在页面刷新时添加 x。

 protected void search(object sender, EventArgs e)
    {
        con.Open();
        cmd.Connection = con;
        cmd.CommandText = "SELECT * FROM Driver WHERE City = '" + JourOrigin.SelectedItem + "' ";//retrieves driver names from table
        dr = cmd.ExecuteReader();
        dr.Read();
        if(Session["city"] != null)

        {
            Session["city"] = null;
            JourOrigin.SelectedValue = null;

        }
        else
        {
            if(dr.HasRows)
            {

            Session["city"] = JourOrigin.SelectedItem.ToString();
            Response.Redirect("~/Account/FindDriver.aspx");
            NoCity.Visible = false;
            }
            else
            {
                DriversJourney.Items.Clear();
                DriversJourney.Items.Add("No Drivers in selected city, try another city");
                NoCity.Visible = true;
                NoCity.Text = "No drivers in selected city, please try another city";
            }

        }
        con.Close();
    }

如果已经有会话，我设法清除会话，但我必须按两次 value 来存储它。每次按下按钮时是否可以“刷新”会话？

Answer 1

你必须试试这个代码：

protected void search(object sender, EventArgs e)
{
    con.Open();
    cmd.Connection = con;
    cmd.CommandText = "SELECT * FROM Driver WHERE City = '" + JourOrigin.SelectedItem + "' ";//retrieves driver names from table
    dr = cmd.ExecuteReader();
    dr.Read();

    if(Session["city"] != null)
    {
        Session["city"] = null;
    }

    if(dr.HasRows)
    {
        Session["city"] = JourOrigin.SelectedItem.ToString();
        Response.Redirect("~/Account/FindDriver.aspx");
        NoCity.Visible = false;
    }
    else
    {
        DriversJourney.Items.Clear();
        DriversJourney.Items.Add("No Drivers in selected city, try another city");
        NoCity.Visible = true;
        NoCity.Text = "No drivers in selected city, please try another city";
    }

    con.Close();
}