不可变引用类型 - 字符串
// assign string from a string literal
string s = "hello";
// assign string from an array of characters
char[] chars = new char[] { 'h', 'e', 'l', 'l', 'o' };
string s = new string(chars, 0, chars.Length);
// assign string from a char pointer, derived from a string
string s;
unsafe
{
fixed (char* charPointer = "hello")
{
s = new string(charPointer);
}
}