How to get the file type description for a file

function GetFileTypeDescription(FileName: String): String;

function GetFileTypeRegKey(FileName: String; out Key: HKEY): Integer;

function GetFileTypeDescription(FileName: String): String;

var hkExtType: HKEY;

     lpszDesc: Array [0..1024] of Char;

     dwSize: DWORD;

begin

  // Attempt to get the registry key for the extension type

  if (GetFileTypeRegKey(FileName, hkExtType) = ERROR_SUCCESS) then

  begin

     // Resource protection

     try

        // Set size of buffer

        dwSize:=SizeOf(lpszDesc);

        // Get the description for the file extension

        if (RegQueryValueEx(hkExtType, nil, nil, nil, @lpszDesc, @dwSize) = ERROR_SUCCESS) then

           // Return the description

           SetString(result, PChar(@lpszDesc), dwSize)

        else

           // Failed to get result

           SetLength(result, 0);

     finally

        // Close the registry key

        RegCloseKey(hkExtType);

     end;

  end

  else

     // Failed to get result

     SetLength(result, 0);

end;

function GetFileTypeRegKey(FileName: String; out Key: HKEY): Integer;

var hkExt: HKEY;

     lpszTypeKey: Array [0..1024] of Char;

     dwSize: DWORD;

     szExt: String;

begin

  // Get the file extension

  szExt:=ExtractFileExt(FileName);

  // Attempt to open the registry key

  result:=RegOpenKeyEx(HKEY_CLASSES_ROOT, PChar(szExt), 0, KEY_READ, hkExt);

  // Check result of open

  if (result = ERROR_SUCCESS) then

  begin

     // Resource protection

     try

        // Set size of buffer

        dwSize:=SizeOf(lpszTypeKey);

        // Query for the default value which is the redirect to the extension type key

        result:=RegQueryValueEx(hkExt, nil, nil, nil, @lpszTypeKey, @dwSize);

        // Check result

        if (result = ERROR_SUCCESS) then

        begin

           // Open the redirect to the extension type key

           result:=RegOpenKeyEx(HKEY_CLASSES_ROOT, @lpszTypeKey, 0, KEY_READ, Key);

        end

     finally

        // Close the opened key

        RegCloseKey(hkExt);

     end;

  end;

end;