How to modify angular component to return message Not Matched Excel

Question

I work on web application asp.net core 2.2 and angular 13 .

How to display message Not Matched Excel from

angular component when compare excel function return

false 

What I have Tried

[Route("ExportNxp")]
public IActionResult ExportNxp()
{
bool areIdentical = ex.CompareExcel(dbPath, InputfilePath, out rowCount, out error);

if (areIdentical == false)
{
return new JsonResult("Not Matched Excel");
}
else 
{
return PhysicalFile(zipPath, "application/zip", Path.GetFileName(zipPath));
}
}

Result I need

 

display message "Not Matched Excel" on angular component where areIdentical = false