Delphi 11.1 TFileOpenDialog.Execute hangs when CoInitializeEx is used in initialization before Forms initialization

The TFileOpenDialog.Execute method can hang if it is called before the COM library has been initialized. This is because the TFileOpenDialog component relies on COM to function correctly.

In Delphi, the CoInitializeEx function is used to initialize the COM library. If this function is called too late or not at all, the TFileOpenDialog.Execute method may hang.

To resolve this issue, you can ensure that CoInitializeEx is called before any code that uses TFileOpenDialog. You can do this by adding a call to CoInitializeEx in your application's main function, before the Application.Initialize call.

Here's an example:

rubyCopy code
program MyProgram;



uses

  Vcl.Forms,

  MyMainForm in 'MyMainForm.pas' {MainForm};



{$R *.res}



begin

  CoInitializeEx(nil, COINIT_MULTITHREADED); // initialize COM

  Application.Initialize;

  Application.MainFormOnTaskbar := True;

  Application.CreateForm(TMainForm, MainForm);

  Application.Run;

  CoUninitialize; // uninitialize COM

end.

In this example, we call CoInitializeEx before Application.Initialize, and call CoUninitialize after Application.Run to uninitialize COM.

By ensuring that COM is initialized before TFileOpenDialog is used, you should be able to avoid the hanging issue.