An interesting question has pop up on the Katmai RS 2008 discussion list today about how to implement a "green bar" group-level report that alternates background color for all rows in a group instance instead of doing this for each row. I attach the report sample I posted. What makes it interesting is that it demonstrates report variables – a new feature in RS 2008.

Before you start analyzing it, you should know that expression evaluation rules in RS 2008 have changed as a result of the new on-demand processing model. As a result, state in class-level instance variables is discarded as you page through the report which makes maintaining state trickier between page requests. However, RS 2008 introduces report variables that guarantee one-time evaluation semantics. I know this may sound to you like Greek, so let me jump into the implementation details:

1. The report has a EvenRow code-behind function that toggles each time it's executed.

2. In the Category group (double-click it to access its properties), an EvenRow group level variable is defined that invokes the EvenRow function once per each group instance.

3. The rest is easy. I set the BackgroundColor property for each textbox to use this variable. BTW, the report uses the SSAS Adventure Works cube.