The string type is a library type and is actaully an array of char or wchar_t. The last character in a string is always null.
The library takes care of managing the memory associated with storing the elements. As well as being less powerful, C-style strings are the root cause of many many security problems, so always use the string library instead.

Literal Strings

Put an L in front:

WriteLine(L"This is my string");

Declare a string

String ^sTemp;
String ^sTemp = "";

Declare A Global String

Just declare in the valraible area. No need to create in the constructor as the string will simply by a null pointer until it is written to (null string handles get constructed when writing to them)
Private: String ^sTemp;

Is String Handle Null?

	if (MyString == nullptr)
		MyString = "";