As part of the migration project I am working on, I have to install, configure and test several Asp.net 1.1 applications on Windows Server 2008 (IIS 7). Asp.Net 1.1 is not part of the default installation, nor is it a feature such as .Net 3.0, but rather a stand alone install that takes some extra steps to get working. If you do a search for asp.net 1.1 on Server 2008, you will get several hits explaining how to install, but that’s not the point of this post.

Basically, Asp.Net 2.0, which is included with Server 2008, is backwards compatible with Asp.Net 1.1. So far, I’ve only found one incompatibility in all of our web applications, and that is related to a change in System.Web.UI.WebControls.ListControl selected index property setter. In .Net 2.0, the setter was re-written such that assigning 0 (zero) to the SelectedIndex property when no items are present in the ListControl will cause an ArgumentOutOfRange exception.

The exact error:

[ArgumentOutOfRangeException: 'lstSites' has a SelectedIndex which is invalid because it does not exist in the list of items. Parameter name: value] System.Web.UI.WebControls.ListControl.set_SelectedIndex(Int32 value) +5138552

I had made a decision that if changes were small enough, I would update the applications in an effort to avoid installing Asp.net 1.1 on Windows Server 2008. This helps by requiring one less thing to install for testing, disaster recovery, and reduces the attack surface of our servers.