I was reading [this question](https://stackoverflow.com/q/2903430/1882077) when I noticed a curious comment underneath:

> 
> not sure what the question is: you can use VB.NET and C# projects in one solution (though I wouldn't recommend doing so).
> 
> 
> 

I do this quite a bit, as we have legacy VB.Net code, and new code is written in C#. Is this really not recommended? Why not?
['https://Stackoverflow.com/questions/15706564', 'https://Stackoverflow.com', 'https://Stackoverflow.com/users/969613/']
The only reason that it wouldn't be recommended is consistency. Most developers prefer to deal with a single language when working on an application. Having a single language also means that your developers only need to know a single language rather than knowing both VB.NET and C# (even though the two are extremely similar).

If you need to mix legacy VB.NET and C#, there's no reason not to.
Mixing code in solutions can get real messy real quickly, its never clear what method you are calling from where, to keep it nice. Develop in separate Solutions, it will keep your projects easier to track and make sure you are not confusing languages inside projects