更新：

这是使用WinHTTP的代码,应尝试从IE接收设置.如果它们可用并且自动检测代理设置或自动配置脚本URL选项被设置,则将执行代理检测.当IE设置不可用时,也会执行自动检测.

免责声明：

以下代码仅在最简单的情况下进行测试,当IE设置可用并且代理设置未被配置为自动检测(没有环境)时.还请注意,本单元中的一些功能,结构和常数是额外的.

unit Unit1;

interface

uses
  Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,Dialogs,StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

type
  HINTERNET = Pointer;
  {$EXTERNALSYM HINTERNET}
  INTERNET_PORT = Word;
  {$EXTERNALSYM INTERNET_PORT}

  PWinHTTPProxyInfo = ^TWinHTTPProxyInfo;
  WINHTTP_PROXY_INFO = record
    dwAccessType: DWORD;
    lpszProxy: LPWSTR;
    lpszProxyBypass: LPWSTR;
  end;
  {$EXTERNALSYM WINHTTP_PROXY_INFO}
  TWinHTTPProxyInfo = WINHTTP_PROXY_INFO;
  LPWINHTTP_PROXY_INFO = PWinHTTPProxyInfo;
  {$EXTERNALSYM LPWINHTTP_PROXY_INFO}

  PWinHTTPAutoProxyOptions = ^TWinHTTPAutoProxyOptions;
  WINHTTP_AUTOPROXY_OPTIONS = record
    dwFlags: DWORD;
    dwAutoDetectFlags: DWORD;
    lpszAutoConfigUrl: LPCWSTR;
    lpvReserved: Pointer;
    dwReserved: DWORD;
    fAutologonIfChallenged: BOOL;
  end;
  {$EXTERNALSYM WINHTTP_AUTOPROXY_OPTIONS}
  TWinHTTPAutoProxyOptions = WINHTTP_AUTOPROXY_OPTIONS;
  LPWINHTTP_AUTOPROXY_OPTIONS = PWinHTTPAutoProxyOptions;
  {$EXTERNALSYM LPWINHTTP_AUTOPROXY_OPTIONS}

  PWinHTTPCurrentUserIEProxyConfig = ^TWinHTTPCurrentUserIEProxyConfig;
  WINHTTP_CURRENT_USER_IE_PROXY_CONFIG = record
    fAutoDetect: BOOL;
    lpszAutoConfigUrl: LPWSTR;
    lpszProxy: LPWSTR;
    lpszProxyBypass: LPWSTR;
  end;
  {$EXTERNALSYM WINHTTP_CURRENT_USER_IE_PROXY_CONFIG}
  TWinHTTPCurrentUserIEProxyConfig = WINHTTP_CURRENT_USER_IE_PROXY_CONFIG;
  LPWINHTTP_CURRENT_USER_IE_PROXY_CONFIG = PWinHTTPCurrentUserIEProxyConfig;
  {$EXTERNALSYM LPWINHTTP_CURRENT_USER_IE_PROXY_CONFIG}

  function WinHttpOpen(pwszUserAgent: LPCWSTR; dwAccessType: DWORD;
    pwszProxyName,pwszProxyBypass: LPCWSTR; dwFlags: DWORD): HINTERNET; stdcall;
    external 'winhttp.dll' name 'WinHttpOpen';
  {$EXTERNALSYM WinHttpOpen}
  function WinHttpConnect(hSession: HINTERNET; pswzServerName: LPCWSTR;
    nServerPort: INTERNET_PORT; dwReserved: DWORD): HINTERNET; stdcall;
    external 'winhttp.dll' name 'WinHttpConnect';
  {$EXTERNALSYM WinHttpConnect}
  function WinHttpOpenRequest(hConnect: HINTERNET; pwszVerb: LPCWSTR;
    pwszObjectName: LPCWSTR; pwszVersion: LPCWSTR; pwszReferer: LPCWSTR;
    ppwszAcceptTypes: PLPWSTR; dwFlags: DWORD): HINTERNET; stdcall;
    external 'winhttp.dll' name 'WinHttpOpenRequest';
  {$EXTERNALSYM WinHttpOpenRequest}
  function WinHttpQueryOption(hInet: HINTERNET; dwOption: DWORD;
    lpBuffer: Pointer; var lpdwBufferLength: DWORD): BOOL; stdcall;
    external 'winhttp.dll' name 'WinHttpQueryOption';
  {$EXTERNALSYM WinHttpQueryOption}
  function WinHttpGetProxyForUrl(hSession: HINTERNET; lpcwszUrl: LPCWSTR;
    pAutoProxyOptions: LPWINHTTP_AUTOPROXY_OPTIONS;
    var pProxyInfo: WINHTTP_PROXY_INFO): BOOL; stdcall;
    external 'winhttp.dll' name 'WinHttpGetProxyForUrl';
  {$EXTERNALSYM WinHttpGetProxyForUrl}
  function WinHttpGetIEProxyConfigForCurrentUser(
    var pProxyInfo: WINHTTP_CURRENT_USER_IE_PROXY_CONFIG): BOOL; stdcall;
    external 'winhttp.dll' name 'WinHttpGetIEProxyConfigForCurrentUser';
  {$EXTERNALSYM WinHttpGetIEProxyConfigForCurrentUser}
  function WinHttpCloseHandle(hInternet: HINTERNET): BOOL; stdcall;
    external 'winhttp.dll' name 'WinHttpCloseHandle';
  {$EXTERNALSYM WinHttpCloseHandle}

const
  WINHTTP_NO_REFERER = nil;
  {$EXTERNALSYM WINHTTP_NO_REFERER}
  WINHTTP_NO_PROXY_NAME = nil;
  {$EXTERNALSYM WINHTTP_NO_PROXY_NAME}
  WINHTTP_NO_PROXY_BYPASS = nil;
  {$EXTERNALSYM WINHTTP_NO_PROXY_BYPASS}
  WINHTTP_DEFAULT_ACCEPT_TYPES = nil;
  {$EXTERNALSYM WINHTTP_DEFAULT_ACCEPT_TYPES}
  WINHTTP_ACCESS_TYPE_DEFAULT_PROXY = 0;
  {$EXTERNALSYM WINHTTP_ACCESS_TYPE_DEFAULT_PROXY}
  WINHTTP_ACCESS_TYPE_NO_PROXY = 1;
  {$EXTERNALSYM WINHTTP_ACCESS_TYPE_NO_PROXY}
  WINHTTP_OPTION_PROXY = 38;
  {$EXTERNALSYM WINHTTP_OPTION_PROXY}
  WINHTTP_OPTION_PROXY_USERNAME = $1002;
  {$EXTERNALSYM WINHTTP_OPTION_PROXY_USERNAME}
  WINHTTP_OPTION_PROXY_PASSWORD = $1003;
  {$EXTERNALSYM WINHTTP_OPTION_PROXY_PASSWORD}  
  WINHTTP_AUTOPROXY_AUTO_DETECT = $00000001;
  {$EXTERNALSYM WINHTTP_AUTOPROXY_AUTO_DETECT}
  WINHTTP_AUTOPROXY_CONFIG_URL = $00000002;
  {$EXTERNALSYM WINHTTP_AUTOPROXY_CONFIG_URL}
  WINHTTP_AUTO_DETECT_TYPE_DHCP = $00000001;
  {$EXTERNALSYM WINHTTP_AUTO_DETECT_TYPE_DHCP}
  WINHTTP_AUTO_DETECT_TYPE_DNS_A = $00000002;
  {$EXTERNALSYM WINHTTP_AUTO_DETECT_TYPE_DNS_A}
  WINHTTP_FLAG_BYPASS_PROXY_CACHE = $00000100;
  {$EXTERNALSYM WINHTTP_FLAG_BYPASS_PROXY_CACHE}
  WINHTTP_FLAG_REFRESH = WINHTTP_FLAG_BYPASS_PROXY_CACHE;
  {$EXTERNALSYM WINHTTP_FLAG_REFRESH}

var
  Form1: TForm1;

implementation

{$R *.dfm}

type
  TProxyInfo = record
    ProxyURL: WideString;
    ProxyBypass: WideString;
    ProxyAutoDetected: Boolean;    
  end;

function GetProxyInfo(const AURL: WideString; var AProxyInfo: TProxyInfo): DWORD;
var
  Session: HINTERNET;
  AutoDetectProxy: Boolean;
  WinHttpProxyInfo: TWinHTTPProxyInfo;
  AutoProxyOptions: TWinHTTPAutoProxyOptions;
  IEProxyConfig: TWinHTTPCurrentUserIEProxyConfig;
begin
  // initialize the result
  Result := 0;
  // initialize auto-detection to off
  AutoDetectProxy := False;
  // initialize the result structure
  AProxyInfo.ProxyURL := '';
  AProxyInfo.ProxyBypass := '';
  AProxyInfo.ProxyAutoDetected := False;
  // initialize the auto-proxy options
  FillChar(AutoProxyOptions,SizeOf(AutoProxyOptions),0);

  // check if the Internet Explorer's proxy configuration is
  // available and if so,check its settings for auto-detect
  // proxy settings and auto-config script URL options
  if WinHttpGetIEProxyConfigForCurrentUser(IEProxyConfig) then
  begin
    // if the Internet Explorer is configured to auto-detect
    // proxy settings then we try to detect them later on
    if IEProxyConfig.fAutoDetect then
    begin
      AutoProxyOptions.dwFlags := WINHTTP_AUTOPROXY_AUTO_DETECT;
      AutoProxyOptions.dwAutoDetectFlags := WINHTTP_AUTO_DETECT_TYPE_DHCP or
        WINHTTP_AUTO_DETECT_TYPE_DNS_A;
      AutoDetectProxy := True;
    end;
    // if the Internet Explorer is configured to use the proxy
    // auto-config script then we try to use it
    if IEProxyConfig.lpszAutoConfigURL <> '' then
    begin
      AutoProxyOptions.dwFlags := AutoProxyOptions.dwFlags or
        WINHTTP_AUTOPROXY_CONFIG_URL;
      AutoProxyOptions.lpszAutoConfigUrl := IEProxyConfig.lpszAutoConfigUrl;
      AutoDetectProxy := True;
    end;
    // if IE don't have auto-detect or auto-config set,we are
    // done here and we can fill the AProxyInfo with the IE settings
    if not AutoDetectProxy then
    begin
      AProxyInfo.ProxyURL := IEProxyConfig.lpszProxy;
      AProxyInfo.ProxyBypass := IEProxyConfig.lpszProxyBypass;
      AProxyInfo.ProxyAutoDetected := False;
    end;   
  end
  else
  begin
    // if the Internet Explorer's proxy configuration is not
    // available,then try to auto-detect it
    AutoProxyOptions.dwFlags := WINHTTP_AUTOPROXY_AUTO_DETECT;
    AutoProxyOptions.dwAutoDetectFlags := WINHTTP_AUTO_DETECT_TYPE_DHCP or
      WINHTTP_AUTO_DETECT_TYPE_DNS_A;
    AutoDetectProxy := True;
  end;

  // if the IE proxy settings are not available or IE has
  // configured auto-config script or auto-detect proxy settings
  if AutoDetectProxy then
  begin
    // create a temporary WinHttp session to allow the WinHTTP
    // auto-detect proxy settings if possible
    Session := WinHttpOpen(nil,WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,WINHTTP_NO_PROXY_NAME,WINHTTP_NO_PROXY_BYPASS,0);

    // if the WinHttp session has been created then try to 
    // get the proxy data for the specified URL else we assign 
    // the last error code to the function result
    if Assigned(Session) then
    try
      // get the proxy data for the specified URL with the
      // auto-proxy options specified,if succeed then we can
      // fill the AProxyInfo with the retrieved settings else
      // we assign the last error code to the function result
      if WinHttpGetProxyForUrl(Session,LPCWSTR(AURL),@AutoProxyOptions,WinHttpProxyInfo) then
      begin
        AProxyInfo.ProxyURL := WinHttpProxyInfo.lpszProxy;
        AProxyInfo.ProxyBypass := WinHttpProxyInfo.lpszProxyBypass;
        AProxyInfo.ProxyAutoDetected := True;
      end
      else
        Result := GetLastError;
    finally
      WinHttpCloseHandle(Session);
    end
    else
      Result := GetLastError;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  Result: DWORD;
  ProxyInfo: TProxyInfo;
begin
  Result := GetProxyInfo('http://www.example.com',ProxyInfo);
  case Result of
    0: 
      ShowMessage(
        'Proxy URL: ' + ProxyInfo.ProxyURL + sLineBreak +
        'Proxy bypass: ' + ProxyInfo.ProxyBypass + sLineBreak +
        'Proxy autodetected: ' + BoolToStr(ProxyInfo.ProxyAutoDetected,True));
    12166: ShowMessage('Error in proxy auto-config script code');
    12167: ShowMessage('Unable to download proxy auto-config script');
    12180: ShowMessage('WPAD detection Failed');
  else
    ShowMessage('Last error: ' + IntToStr(Result));
  end;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  ReportMemoryLeaksOnShutdown := True;
end;

end.

对于替代Delphi代码,您可以检查this tip.

以下是如何使用获取的代理设置设置TIdHTTP的示例(实际上您只需解析获取的代理URL并将其传递到ProxyServer和ProxyPort属性)：

uses
  IdGlobal;

procedure TForm1.Button1Click(Sender: TObject);
var
  S: string;
  Result: DWORD;
  ProxyInfo: TProxyInfo;
begin
  Result := GetProxyInfo('http://www.example.com',ProxyInfo);

  if Result <> 0 then
    IdHTTP1.ProxyParams.Clear
  else
  begin
    S := ProxyInfo.ProxyURL;
    IdHTTP1.ProxyParams.ProxyServer := Fetch(S,':');
    IdHTTP1.ProxyParams.ProxyPort := StrToInt(S);
  end;
end;