Check if string has space in between (or anywhere)

How about:

myString.Any(x => Char.IsWhiteSpace(x))

Or if you like using the "method group" syntax:

myString.Any(Char.IsWhiteSpace)

If indeed the goal is to see if a string contains the actual space character (as described in the title), as opposed to any other sort of whitespace characters, you can use:

string s = "Hello There";
bool fHasSpace = s.Contains(" ");

If you're looking for ways to detect whitespace, there's several great options below.