C# utilizes a double forward slash (//) to indicate the rest of the line is a comment. This is inherited from C++.
public class Foo
{
// a comment
public static void Bar(int firstParam) {} //Also a comment
}
Multi-line comments can be indicated by a starting forward slash/asterisk (/*) and ending asterisk/forward slash (*/). This is inherited from standard C.
public class Foo
{
/* A Multi-Line
comment */
public static void Bar(int firstParam) {}
}