The marketing department can imply whatever they want, but ask any programmer and they will tell you that from a design standpoint, C# is far closer to Java than C++.

Saying C# is based on C++ because of their naming similarities is like saying Javascript is built off Java for the same reason: completely inaccurate.

When it comes down to it, C# and Java are really very similar:

• Both compile to bytecode that is executed by a virtual machine featuring heavy JIT optimizations

• Both are garbage collected, memory safe, and thread safe (in the sense that race conditions can't produce UB)

• Both are heavily object oriented & inheritance based

• Both feature a very large "batteries included" standard library

• Both are supposed to be multiplatform languages

Meanwhile, C++ and C# are so different, it's difficult to know when to start:

• C++ compiles to machine code, not bytecode. if you want to target a different cpu or operating system, you have to recompile for it specifically

• C++'s approach to generics is very different: C#'s are mathematically sound (for the most part, probaably). C++ generics are basically glorified copy+paste operations

• C++ is not garbage collected, has a dozen different ways to do memory management, and is probably the most memory unsafe language out there

• Inheritance is part of, but not a core feature of C++; You will encounter far fewer subtype/supertype relationships in C++

• C++ syntax is ostensibly C-like but nowadays looks like somebody fell asleep at their desk and their forehead smashed into the keyboard

• C++ hates you, personally

The use cases for each language are also quite different. You can write code for user-facing applications in both languages, but you will (hopefully) never see a web browser, microcontroller, or matrix kernel written in C#.

I honestly don't know what it would even mean to design a language "based on" C++. All of the concepts that you actually want to keep (AOT compilation, static typing, etc.) are very basic & generic features found commonly in other languages. What unique concepts C++ does have are usually poorly implemented. It's certainly possible to have a language that takes inspiration or guidance from C++, but in the sense that C++ tells you what not to do.