Not completely interoperable. At least initially (and as far as I'm aware ever). VB.Net never could understand the unsigned integral & char types. If you used u

Not completely interoperable. At least initially (and as far as I'm aware ever). VB.Net never could understand the unsigned integral & char types. If you used unsigned types in C#, those members wouldn't be BCL compatible and at sufficient warning level, you had to annotate members with [BCLCompliant(false)] if my memory serves correctly. There were other language constructs at the time that werent 1:1 parity at v1.0, but in nearly 20 years time, I forget.