Passing session variable from page to page

问题

I'm wondering what is my issue on passing a variable from page to page using asp.net session.

I've stripped the code down to just one text box to see whats going on. I'm just trying to take the value of a text box and display it on a confirmation page. When the button is clicked it transfers me to the second page but there label is blank. Yes my post back url is pointing to the second page.

Here is the button click:

protected void submit_Click(object sender, EventArgs e)
{
    string name = txtFirstName.Text.Trim();
    Session["name"] = name;
}

Here is the page load of the second page:

protected void Page_Load(object sender, EventArgs e)
{
    lblName.Text = (string)(Session["name"]);
}

Unless I've been looking at this to long and missed something. I've already read "How to: Read Values from Session State" from MSDN.

回答1:

You say that you've set the PostBackUrl to your second page. If you're going to do it that way, you need to use Page.PreviousPage to get access to your textbox. But this is the easiest way:

Firstly, leave the PostBackUrl alone. Setting the PostBackUrl to your second page means that you're telling the SECOND PAGE to handle your button click, not the first page. Hence, your session variable never gets set, and is null when you try to pull it.

This should work for ya.

And yes, you can also do this with a QueryString, but if its something that you don't want the user to see/edit, then a Session variable is better.

 protected void submit_Click(object sender, EventArgs e)
 {
      string name = txtFirstName.Text.Trim();
      Session["name"] = name;
      Response.Redirect("PageTwo.aspx");
 }

Then in the second page (You don't REALLY need the ToString()):

 protected void Page_Load(object sender, EventArgs e)
 {
      if (Session["name"] != null)
      {
           lblName.Text = Session["name"].ToString();
      }
 }

EDIT -- Make sure that your button click actually gets fired. Someone can correct me wrong on this, as I do most of my work in VB.NET, not C#. But if you don't specify the OnClick value, your function won't get called.

 <asp:Button ID="Button1" runat="server" Text="Click Me!" OnClick="submit_Click" />

回答2:

The code you have posted looks fine, so your problem is probably with setup.

Check this link ASP.NET Session State Overview and pay particular attention to the sections on Cookieless SessionIDs and Configuring Session State.

回答3:

I don't think you added the session. This is how I have done mine.

First Page

protected void btnView_Click(object sender, EventArgs e)
        {
            foreach (ListItem li in lbxCheckDates.Items)
            {
                if (li.Selected == true)
                {
                    lblMessage.Text = "";
                    string checkDate = lbxCheckDates.SelectedItem.Text;
                    Session.Add("CheckDates", checkDate);
                    Page.ClientScript.RegisterStartupScript(
                    this.GetType(), "OpenWindow", "window.open('Paystub.aspx','_newtab');", true);
                }
            }
        }

Second Page

protected void Page_Load(object sender, EventArgs e)
       {
            string checkDate = (string)(Session["CheckDates"]);

            //I use checkDate in sql to populate a report viewer
        }

So with yours, I think you need..

protected void submit_Click(object sender, EventArgs e)
    {
        string name = txtFirstName.Text.Trim();
        Session.Add("Name", name);
    }

I think what you have in the second page should work, but if it doesn't, add ToString() to it like..

lblName.Text = (string)(Session["name"]).ToString();

Let me know if this helps!

回答4:

Are you doing a redirect after setting the session variable on the first page, if so you it will not work correctly (unless you know the trick). Checkout this article on making it work. Basically, the way to make this work is to the overload redirect method.

Response.Redirect("~/newpage.aspx", false);

The false parameter prevents .net from terminate processing on the existing page (that actually writes out the session state)

回答5:

For Second Page

protected void Page_Load(object sender, EventArgs e)
{
    if (Session["value"] != null)
    {
        Label1.Text = Session["value"].ToString();

    }
    else 
    {
        Label1.Text = "Sorry,Please enter the value  ";
    }
}

回答6:

You can use Server.Transfer() instead of Response.Redirect()

回答7:

For first page, use this:

protected void Button1_Click(object sender, EventArgs e)
{
    string value = TextBox1.Text;
    Session["value"] = value;
    Response.Redirect("~/Sessionpage.aspx");
}

来源：https://stackoverflow.com/questions/19668500/passing-session-variable-from-page-to-page

标签

ASP.NET

session-variables