Wndows shell programming-call "open method ..." Dialog Box to open the document

Example:
Add a shellapi unit to use

VaR
Filepath: string;
Shellreturn: integer;
Begin
Filepath: = file path + file name
If filepath <> ''then
Begin
Shellreturn: = ShellExecute (handle, pchar ('open'), pchar (filepath), nil, nil, 1 );
If shellreturn <= 32 then
Case shellreturn
0: MessageBox (handle, 'the system resource is insufficient. An error occurred while opening the file! ', 'Failed', mb_ OK + mb_iconstop );
Se_err_associncomplete: MessageBox (handle, 'the specified file name does not comply with the Windows normal', 'failed', mb_ OK + mb_iconerror );
Se_err_fnf: MessageBox (handle, 'the specified file is not found', 'failed', mb_ OK + mb_iconerror );
Se_err_oom: MessageBox (handle, 'There is not enough memory to complete the operation. Opening the file failed! ', 'Failed', mb_ OK + mb_iconstop );
Se_err_pnf: MessageBox (handle, 'not found in the specified directory', 'failed', mb_ OK + mb_iconerror );
{When the returned value indicates that this type of file is not registered in the system, the system 'open method... 'dialog box is called}
Se_err_noassoc: winexec (pchar ('rundll32 shell32, openas_rundll '+ filepath), sw_showdefault );
Else
MessageBox (handle, 'file opening failed', 'failed', mb_ OK + mb_iconerror );
End;
End;
End;

Here:
ShellExecute (handle, pchar ('open'), pchar (filepath), nil, nil, 1); used to directly open registered files (or web pages, Program )

Winexec (pchar ('rundll32 shell32, openas_rundll '+ filepath), sw_showdefault); used to call the 'open method...' dialog box to open the file