Question

It seems to me that ASP.net queues up all requests that use the same Session ID. Let’s say you’ve got 3 pages.

Default.aspx

protected void Page_Load(object sender, EventArgs e)
{
    Session["asdf"] = "LOLZ";
}

Hitting this page would obviously create a new session if one doesn’t exist.

X-AspNet-Version: 2.0.50727
Set-Cookie: ASP.NET_SessionId=ibjphuv0aiafqi453tyze345; path=/; HttpOnly

Then you hit Hang.aspx

protected void Page_Load(object sender, EventArgs e)
{
    Thread.Sleep(10000);
}

And immediately after you hit any other page that this session ID would be passed to, doesn’t matter if it does anything, let’s call it Test.aspx.

The sequence for loading is like so.

Request            Timeline
"GET /"            |*|
"GET /Hang.aspx"       |******************************************|
"GET /Test.aspx"            |**************************************|

I guess my question is how do I disable this feature. I understand it’s useful to have so that session state can be more predictable, however in my case a long running reports page load is killing users’ ability to multitask.

Answer 1

This behaviour is by design; no concurrent access to the session state is allowed. Requests with same SessionID will be locked exclusively to prevent potential corruption of its state.

To get around this you can disable session state in your page directive.

<%@ Page EnableSessionState="false" %>

Read “Concurrent Requests and Session State” here http://msdn.microsoft.com/en-us/library/ms178581.aspx for more.

Setting EnableSessionState="ReadOnly" will prevent that page from gaining an exclusive lock on the SessionState (but the page itself would have to wait for other non-ReadOnly requests by the user to finish before loading).

(This is a copy and paste of my answer to this question ASP.net site: Long-loading page for user puts all other page loads for user on Hold)