I spotted an old post from Brad Abrams on breaking changes for .NET 1.1 apps recompiled with 2.0. The links had moved but are still relevant…
My own observations from converting projects are a little higher level in that I’m also interested in what effort you’re liable for when converting, and also things to watch out for if (like me) you’re having to persist a ‘shared’ code base of 1.1 and 2.0 core libraries (temporarily) while you migrate all your client apps.
ASP.NET Projects. This includes Web Service projects. You’ll find that you’ll probably have to reconstruct these projects based on the content files and you’ll also need to make a decision on the model you’re going to use for debugging – i.e. whether to use the new debugging host (removing IIS from the debugging equation) and whether to use a dynamic or static port. Steer clear of the ‘Web Site’ project too as this could leave you confused for hours wondering why you can’t debug anything – look for the ASP.NET projects. More info on the ASP.NET side can be found from Peter Laudati’s post. Microsoft also have an article covering conversion of ASP.NET projects
DataSets. These have changed in that a ‘designer’ file is now the main source file (apart from the .xsd). If you’re sharing DataSets across 1.1 and 2.0 projects just share the .xsd file otherwise you’ll be asking for trouble as the other generated files are incompatible. Any structural changes to a DataSet in one project (say .NET 1.1) will not be reflected in the corresponding 2.0 project. You’ll need to check out the XSD in both places (assuming you’re using VSS) and build both in order to avoid breaking one of the projects.
Windows Forms. I’ve had a recent experience where the InitializeComponent() method in a form (edited with VS 2005) places calls that aren’t compatible with .NET 1.1. The code compiles (as below) but ‘exception thrown by target of an invocation’ gets thrown on the following line…
This is because the control (a PictureBox in this case) doesn’t implement ISupportInitialize in .NET 1.1 but does in 2.0. The equivalent in 1.1 is SuspendLayout()
This would just be one example of something that’s syntactically correct, but could fail at runtime.