PERM process: Letters of recommendation from previous employer

[myvisastatus]

This is regarding PERM process. My attorney has asked me to get letters of recommendation from my previous employers. The programming languages, technologies and tools which would be mentioned in the advertisement placed by my current company will have to match with the skill set with previous employers?

(e.g.: With my previous employers, I have experience in Java. Currently, I am working on .NET. So, mentioning skill set of .NET in the job advertisement will harm me, if I will be having experience of Java (and not .NET) on my recommendations from my previous managers?)

Also, I have Masters degree, during which I have worked on .NET. I can get the recommendations from my project guide. Will that be of any help?

Thanks in advance!