Migrating a project from V2 to V3 LLBLGen project was a huge pain. Since I work in 30+ projects that use V2, I decided to write out all the not-so-obvious steps required.
Half the battle is just finding these links:
Use git or just copy your files into another directory. You'll be making some fierce changes to references, code, & your project file.
In LLBLGen V2 the project file is a binary .lgp file. In V3 it becomes an XML .llblgenproj so you need to convert your project file.
I wish you could just open your old project in the new program and it would automatically convert it for you, but it is WAAAAY more complicated.
At this point, you can open the .llblgenproj with V3 & generate code just like normal.
Now your *.dll references are messed up so your project doesn't build anymore. For SqlServer, projects have 3 dependencies:
You need to delete these out of your lib (in your project), delete them from your project references, & clean your solution.
Now re-add them in Visual Studio by clicking "Add Reference" then selecting them from your GAC. You need to add version 22.214.171.124 of each assembly:
In my opinion you should set these as 'copy local', then build, then copy them out of the bin into a lib, then reference the ones in your lib (instead of the GAC). This makes your project build on a computer that doesn't have LLBLGen3 installed.
SelfServicing V3 got rid of both DbUtils classes so you need to delete them. They are:
The connection string name changed from v2 to v3, so you'll need to change your web or app config from
<add name="Main.ConnectionString" ...
to this new version:
<add name="Main.ConnectionString.SQL Server (SqlClient)" ...