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<TITLE>BDE API Examples (DbiRegisterCallback)</TITLE>
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<h2>BDE API Examples (DbiRegisterCallback)</h2>
Registers a callback function for the client application.
<hr size=2 noshade>

<H3>Example 1: Create a callback that handles the condition of a missing 
.MDX file for a dBASE file or a missing .CDX file for a FoxPro file:</H3>
<PRE>//Function called by DbiRegisterCallBack
function myfunc(ecbType : CBType; iClientData : LongInt; 
   pCbInfo : pCBInputDesc): CBRType; stdcall;
const
   READONLY = 'Read Only';
   FAILOPEN = 'Fail Open';  //The default
   OPENANDDETACH = 'Open and Detach';
var
  counter : integer;
begin
  case ecbtype of
    cbINPUTREQ:  //It's a callback of cbINPUTREQ type
      if pcbInfo.eCbInputId = cbiMDXMIssing then
      begin
        {
        //Simple loop to list all modes, could be used to give used
        //to give a choice
        for counter:= 0 to pcbInfo.iCount-1 do
          showmessage(pcbInfo.acbEntry[counter].szKeyWord + #13 +
                   pcbInfo.acbEntry[counter].szHelp);
        }
        for counter:=0 to pcbInfo.iCount-1 do
          if pcbInfo.acbEntry[counter].szKeyword = OPENANDDETACH then
          begin
            pcbInfo.iSelection:=counter+1;
            pcbInfo.bSave := FALSE;
            break;
          end;
      end
      else  //if
        ShowMessage('Unexpected eCbInputId');
  else  //Case
    ShowMessage('Unexpected ecbType')
  end;
end;

//Register the callback and open the table
procedure TForm1.Button2Click(Sender: TObject);
var
  cbinfo : CBInputDesc;
begin
  session.open;
  Check(DbiRegisterCallBack(
   nil,                          //Cursor (Optional)
   cbINPUTREQ,                   //Type of Callback
   longint(0),                   //Pass-through client data
   sizeof(CBInputDesc),          //Callback buffer len
   @cbinfo,                      //Pointer to callback function
   @myfunc                       //Call back fn being registered
));
   Table1.Open;

   //Unregister the callback
   Check(DbiRegisterCallBack(nil, cbINPUTREQ, 0, sizeof(CBInputDesc), nil , nil));
end;</PRE>

<hr size=2 noshade>
<H3>Example 2: Register the cbTABLECHAGNED callback for notification when a Paradox
table's data has changed</H3>
This example is too complicated to be shown here.  A sample 
<A HREF="/devsupport/bde/files/tablechanged.zip">Delphi registration component with an example</A> 
is available that will do all the registration work for you. Simply install the new TTable 
component (TRegisterTable in RegisterTable.pas) and compile the included project. This component
will work with all table types, but will only use the callback with Paradox table types.

<hr size=2 noshade>
<p>

<A HREF="/devsupport/bde/bdeapiex/index.html">Back to BDE API Reference Page</A>

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<FONT SIZE = 2><i><b>DISCLAIMER:</b> You have the right to use this technical information subject to 
the terms of  the No-Nonsense License Statement that you received with the Borland product to which 
this information pertains.</FONT></i></B>


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