Is it true that dotnet code "open"?

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Dear Group:
Having spent quite some time with VB 6 and prior, I have been considering
moving to VB.Net and ASP.Net. However, some developers here (Java) have told
me that the code is not "secure" in that it is easy to decompile. Can anyone
shed some light on this regarding the two languages listed?

Thanks in advance,
Carl