If your store is primarily C# , and this is really what you want your project to be developed, I would advise another developer to find out C# rather than compromise your project in order to take into account the ignorance of one of your Team Members. This is not to overwhelm your other team member, but if he / she understands .Net well at all, then there is no reason this person could not learn C #.
We have a combination of both in my company, however, the choice of using VB.Net always depends on whether the existing VB6 application is ported to .Net, and in this case it makes sense to use VB.Net, since it needs less code to be rewritten (in most cases).
But we never allowed the developer’s skills to determine whether to use C # or VB.Net, we would choose the best tool for the job, and this should always be the point of decision.
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