gistfile1.txt

Is there any common name for all these types?

string
char
int
long
short
double
float
byte
bool
DateTime

Not all primitives.
Not all value types.

I consider them primitives. DateTime is kind of an odd choice on this list; why that and not TimeSpan as well? I think the list without DateTime is "primitives" and with DateTime/TimeSpan is maybe "intrinsics"?

The list isn't exhaustive. TimeSpan should be on there, as should all the u* types, and decimal, enums, and probably some more. Everything except class, basically.

string is a class, but I see what you mean. I think primatives is a pretty good description, there the stuff you compose to represent data. I don't think you'd want to inculde all value types either, there's a lot of yuck stuff in the values types like IntPtr, SqlInt and Nullable.