Difference.........

Just about everything.

The list of similarities is far, far smaller than the list of differences. Even when they are similar, generally, it is an illusion.

Remember, C begat C++, which begat C# (via a lot of brothers, cousins, and little ones with webbed fingers.

It would take a major essay to list the differences! I suggest you Google for just that.

Come on... you don't know how to use google?

C and C# are two different worlds: they just share some keywords and constructs.

A big difference is that the C programming language is not object oriented while the C# is.

The C++ programming language was initially born as an extension of the C to support the object oriented programming; the C# is too near to C++ than how it is to C (however C++ and C# are very different in many aspects).

To get an idea of what the defferences are, you can read the articles below, from Wikipedia:

C (programming language)[^]
Object-oriented programming[^]
C++ (programming language)[^]
C# (programming language)[^]