dll读写注册表问题。

Question

我想用DLL来读写注册表，用来连接数据库，各位给点建议。我下边写的哪里错了？为什么通不过？编译没问题，但是无法正确运行。
DLL文件：
library PDbDll;
uses
  SysUtils,Windows,Registry,
  Classes;{$R *.res}function GetDataBase(value: integer):string; export;
var
  regcode: TRegistry;
begin
  if value=1 then
    begin
      regcode:= TRegistry.Create;
      Regcode.RootKey:= HKEY_LOCAL_MACHINE;
      if regcode.OpenKey('\system\BloodBank',false) then
        result:= regcode.ReadString('database');
    end;
end;
exports
GetDataBase;begin
end.
//////////////////////
调用程序
unit UDbTest;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;type
  TForm1 = class(TForm)
    EdServer: TEdit;
    Button1: TButton;
    edDataBase: TEdit;
    edUserName: TEdit;
    edPwd: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation
{$R *.dfm}
function GetDataBase(i: integer):string;external'PDbDll.dll';procedure TForm1.Button1Click(Sender: TObject);
var
 ii0:integer;
begin
  ii0:=1;
  edDataBase.Text:= GetDataBase(ii0);
end;end.
/////////////////////
谢谢!

Answer 1

请参考：
http://community.csdn.net/Expert/topic/4242/4242766.xml?temp=.3676264Procedure WriteReg;  //写注册表
var
  reg:Tregistry;
  vServerName, vDataBase, vSa, vPass : String;
begin
  reg:=Tregistry.create;
  reg.rootkey:=HKEY_LOCAL_MACHINE;
  if reg.openkey('\SOFTWARE\MYSOFT',False) then
  begin
  end
  else begin
    reg.openkey('\SOFTWARE\MYSOFT',True);
    reg.WriteString('vServerName','MYServer');
    Reg.WriteString('vDataBase','DataTest');
    Reg.WriteString('vSa','sa');
    Reg.WriteString('vPass','123456');
    reg.closekey;
  end;
  Reg.Free;
end;Procedure ReadReg;  //读注册表
var
  reg:Tregistry;
  vServerName, vDataBase, vSa, vPass : String;
begin
  reg:=Tregistry.create;
  reg.rootkey:=HKEY_LOCAL_MACHINE;
  if reg.openkey('\SOFTWARE\MYSOFT',False) then
  begin
  end
  else begin
    reg.openkey('\SOFTWARE\MYSOFT',True);
    vServer := reg.ReadString()('vServerName');
    vDataBase := reg.ReadString('vDataBase');
    vSa := Reg.ReadString('vSa');
    vPass :=Reg.ReadString('vPass');
    reg.closekey;
  end;
  Reg.Free;
end;

Answer 2

DLL项目：
library PDbDll;uses
  SysUtils,Windows,Registry,
  Classes;{$R *.res}function GetDataBase(value: boolean):string;stdcall; export;
var
  regcode: TRegistry;
begin
  if value=True then
    begin
      regcode:= TRegistry.Create;
      Regcode.RootKey:= HKEY_LOCAL_MACHINE;
      if regcode.OpenKey('\SoftWare\BloodBank',false) then
        result:= regcode.ReadString('database');
        regcode.CloseKey;
      regcode.Free;
    end;
end;
调用方：
unit UDbTest;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;type
  TForm1 = class(TForm)
    EdServer: TEdit;
    Button1: TButton;
    edDataBase: TEdit;
    edUserName: TEdit;
    edPwd: TEdit;
    Label1: TLabel;
    Label2: TLabel;
    Label3: TLabel;
    Label4: TLabel;
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation
function GetDataBase(i: boolean):string;stdcall;external'PDbDll.dll' ;{$R *.dfm}
procedure TForm1.Button1Click(Sender: TObject);
var
 ii: Boolean;
begin
  ii:=True;  edDataBase.Text:= GetDataBase(ii);
end;end.
//////////////////
调用的结果都对的，但是提示：Invalid pointer operation.

Answer 3

不要返回STRING类型数据，试下用返回PCHAR类型数据应该就行了

Answer 4

即动态库中函数function GetDataBase(i: integer):string改为
function GetDataBase(i: integer):PCHAR