1/ In early 2004 we were heads down executing on Edit and Continue across a large contingent of teams. There had been several iterations of scoping, redesigns, and customer feedback.

2/ We had a weekly meeting every Thursday morning when representatives from each of the teams would get together and review progress. It was fairly heavy weight, but there were so many teams involved that it was necessary to have a regular sync.

3/ Regardless, E&C was coalescing, but teams were stretched thin working diligently to enable scenarios, improve performance, fix bugs, etc. It had been a month or so since we decided to add support for C# to the matrix as well, so folks were a bit stressed.

4/ That set the stage for the meeting that we had on the first Thursday in April. A debugger PM named Habib Heydarian ran the meeting and after a brief intro he gave me a ring to come in and present.

5/ I walked in and handed out a document that I had written up, titled DCR: C# Edit and Continue for Venus. DCR meant design change request, and Venus was the design-time code name for ASP .NET support.

Incremental rebuild was a feature of the C# compiler which was meant to increase the throughput after an initial build. It worked on the principle that changes in between builds are localized, and that the information gathered by the compiler from previous builds wouldn't be

entirely invalidated; specifically, some of the information and, indeed, the assembly itself could be updated in an incremental fashion resulting in faster builds.

Both the VS 2002 and VS 2003 compilers exposed this option through the /incr switch on the command line, and the ‘Incremental Rebuild’ option in the Advanced tab of Project Properties. In 2002 incremental rebuild was enabled by default for all project types.

After we shipped 2002 we noticed that we started to get a large number of bugs (internal compiler errors - ICEs – the worst kind) which were a direct result of the incremental rebuild feature.

These bugs derived from the complexities involved in correctly implementing incremental rebuild and the problems associated with testing it. Consequently, for 2003 we fixed all known issues with incremental rebuild but subsequently turned it off by default for all projects.