为什么这两句的结果是不同呢?

Question

错误:
  var
    Buffer:array of Char;
    keyhand:HKey;
    datasize:integer;
  begin
    RegOpenKey(HKEY_CURRENT_USER,'SoftWare\ChengSoft\VBScript Editor',keyhand);
    RegQueryValueEx(keyhand,item,0,0,0,@datasize);
    setlength(Buffer,datasize);
    RegQueryValueEx(keyhand,item,0,0,@Buffer,@datasize);
    RegCloseKey(keyhand);
  end;
_____________________________________________________________
正确:
  var
    Buffer:array[00..255] of Char;
    keyhand:HKey;
    datasize:integer;
  begin
    RegOpenKey(HKEY_CURRENT_USER,'SoftWare\ChengSoft\VBScript Editor',keyhand);
    RegQueryValueEx(keyhand,item,0,0,@Buffer,@datasize);
    RegCloseKey(keyhand);
  end;
_____________________________________________________________
问:如何以动态数组变量的形式,修改第一种方法,让其正确.

Answer 1

错误:
  var
    Buffer:array of Char;
    keyhand:HKey;
    datasize:integer;
  begin
    RegOpenKey(HKEY_CURRENT_USER,'SoftWare\ChengSoft\VBScript Editor',keyhand);
    RegQueryValueEx(keyhand,item,0,0,0,@datasize);
    setlength(Buffer,datasize);
    RegQueryValueEx(keyhand,item,0,0,@Buffer,@datasize);
    RegCloseKey(keyhand);
  end;
_____________________________________________________________
正确:
  var
    Buffer:array[0..255] of Char;
    keyhand:HKey;
    datasize:integer;
  begin
    RegOpenKey(HKEY_CURRENT_USER,'SoftWare\ChengSoft\VBScript Editor',keyhand);
    RegQueryValueEx(keyhand,item,0,0,@Buffer,@datasize);
    RegCloseKey(keyhand);
  end;
_____________________________________________________________
问:如何以动态数组变量的形式,修改第一种方法,让其正确.

Answer 2

RegQueryValueEx(keyhand,item,0,0,0,@datasize);这句

Answer 3

RegQueryValueEx(keyhand,item,0,0,0,@datasize);是错误的