First, you would have a hard time convincing them to take the job and stick with it unless they were desperate for work or if you promised them that you were converting from VB.NET to C#.

Secondly, there are a number of very worthwhile and useful parts of the Microsoft.VisualBasic namespace along with the not-so-great legacy features. Even some legacy functions, like Mid, can be useful in some situations. The trick for the good VB.NET developer is to know what to use, what not to use and when to use it. A C# programmer is likely to simply throw out anything that carries a “VB stigma”, including parts of the core language, which can easily result in VB code as inefficient as overuse of VB6 methods.