Which microsoft certification I should go for?

Hi,

I am working as a software developer .net in telecom domain (fiber optics) and have 2.1 yrs of experience. I want to go for certification but want to know which microsoft certification exam can really boost my windows application development expertise as per current industry demand. I am looking for long term .net career in telecom domain and will try for US/UK based jobs in telecom domain as a software developer. Your suggestion will be highly appreciated.thnkx :)