We are currently in the process of upgrading one of our applications to .Net 4.0. Aside from us geeks wanting to always use latest and greatest technologies, an immediate business need for Silverlight 4.0 features justified our upgrade endeavor. The following is a summary of some issues we ran into with our web project:

 

For security purposes, the IIS 7 .Net 4.0 ISAPI filter is disabled. “Allow” it from the ISAPI and CGI Restrictions screen as shown:

 

Figure 1 - Allowing ASP.Net 4.0 ISAPI Filter

 

By default the Web Setup Project only requires the .Net Framework 4 Client Profile to be installed on target system, which offers a lighter weight install for client machines consuming .Net 4.0 applications. However, using certain .Net 4.0 features requires the full .Net 4.0 Framework as outlined in this link: http://msdn.microsoft.com/en-us/library/cc656912.aspx. We hence needed to update the installer to require the complete .Net 4.0 Framework on the target machine and to prompt for its installation if needed.

 

To accomplish this goal, we updated the installer’s launch conditions to check for .Net 4.0 as well as the installer prerequisites as shown:

 

 

Figure 2- Ensure Web Setup Project runs on full .Net 4.0 version