Dynamic loading and binding of DLLs

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Dynamic loading and binding of DLLs (Views: 712)

Problem/Question/Abstract:

Dynamic loading and binding of DLLs

Answer:

Sometimes you may need to load a DLL at runtime, for example

if you have a couple of different DLLs to choose between
to have a concept for optional functionality.

This small source code shows how to load the DLL with LoadLibrary and use the returned handle to access (bind) the functions that are contained:

{ function declaration }

type
    TfncCnx = function(s: string): THandle;

var
    cnx: TfncCnx;
begin
  { load the DLL and get the function's address }
    h := LoadLibrary('myDll');
  if h = 0 then
  begin
    ShowMessage('DLL not available');
  end
  else
  begin
     @cnx := GetProcAddress(h, 'myProc');
    if @cnx = nil then
    begin
      { function not found.. misspelled? }
      ShowMessage('blub');
    end
    else
    begin
      { call the function as usually }
      x := cnx('alpha');
    end;
    { unload the DLL }
      FreeLibrary(h);
  end;
end;

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