Upgrade to .NET Framework 2.0

Our company has an application built and running against .NET Framework 1.1. The client side is a Windows Forms control embedded in IE. So the client requires .NET Framework. The control makes Web service calls to a Web server and Web services make ADO.NET calls to a SQL Server database.

Recently I tested the app under .NET Framework 2.0 with all the combinations: client 1.1 + server 2.0, client 2.0 + server 1.1, client 2.0 + server 2.0. It worked very well and no change was made. Amazing!

I found that MSDN documentation in this area is very poor. So I record a couple of things that I feel useful. Assume that .NET Framework 2.0 is installed on top of an existing .NET Framework 1.1.

• IE always loads .NET Framework 2.0 no matter which version of .NET Framework your Windows Forms control is built against if both 2.0 and 1.1 are present. This is against .NET rule. The rule says that, if the version of the .NET Framework that the application was built against is present on the computer, the application runs on that version. Our control was built against .NET 1.1, but .NET 2.0 was loaded by IE instead of .NET 1.1.
• If .NET 2.0 is installed on top of .NET 1.1, the combo box on the ASP.NET tab in IIS will contain two entries: .NET 2.0 and .NET 1.1. But .NET 1.1 remains the default. This is very good because it causes the least pain when upgrading of servers. If you want to run your Web app against .NET 2.0, then you need to change the framework version to 2.0 on the ASP.NET tab.