J2EE and .Net working together.
There are some options for you to think about.
1. Ja.net: open source and free. one way java working in .net project
2. Ikvm: open source free, working very good. one way java working in .net project
3. Jnbridgt: not free. have growing fast. integration more deep than both 1 and 2.
4. codemesh: not free. have growing fast. integration more deep than both 1 and 2.
remark: IIS integration with tomcat or apache, which makes the two side have more touch.
refence:
