How to upgrade from .NET Framework 1.0 to .NET Framework 3.5

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With .NET 3.5 being released about the end of the year at the same time as Visual Studio 2008 it's a good time to look around for any remaining .NET 1.0 or .NET 1.1 applications and consider upgrading them. How do you do it? Does it seem overwhelming? Read on here's some advice…

  • First upgrade your code from .NET 1.0 to .NET 1.1 using Visual Studio 2003. It has a project upgrade tool with some assistance.
  • Next use Visual Studio 2008 to upgrade the project from .NET 1.1 to .NET 2.0. The upgrade wizard here does not change your code. It will show you warnings for things that you have to change but you will have to go change them. You also have to fix all your new compile errors and do a full retest.
  • Once you're at .NET 2.0 the migration to .NET 3.0 and .NET 3.5 is easy. It's primarily just about using the new features available in these new versions of the framework. All your existing code should work fine, in fact you most likely wont even need to recompile.

The .NET 1.1 -> .NET 2.0 breaking changes are detailed here: https://msdn2.microsoft.com/en-us/netframework/aa570326.aspx

Here's a helpful blog entry from Brad Abrams on upgrade experience:
https://blogs.msdn.com/brada/archive/2007/01/15/real-world-customer-experience-in-migrating-from-net-framework-1-1-to-2-0.aspx

Here's another great post on this topic deom Daniel Moth:
https://www.danielmoth.com/Blog/2007/10/migrating-from-net-framework-v1x-to.html