Why are C#/.NET strings length-prefixed and null terminated?

Question

After reading What's the rationale for null terminated strings? and some similar questions I have found that in C#/.NET strings are, internally, both length-prefixed and null terminated like in BSTR Data Type.

What is the reason strings are both length-prefixed and null terminated instead of eg. only length-prefixed?

Answer 1

Length prefixed so that computing length is O(1).

Null terminated to make marshaling to unmanaged blazing fast (unmanaged likely expects null-terminated strings).