I can’t find an asp.net core c# function or code example to test if an HTTP reponse is programmatic.

In asp.net (core) 8.0 c#, I am determining if a web response is html or javascript with

               if ( context.HttpContext.Response.StatusCode < 400 &&
                   (
                   context.HttpContext.Response.ContentType.Contains("text/javascript") ||
                   context.HttpContext.Response.ContentType.Contains("application/javascript") ||
                   context.HttpContext.Response.ContentType.Contains("text/html") ||
                   context.HttpContext.Response.ContentType.Contains("text/xml")
                   ))
               { 
                       // Proceed with operations on replies that might be programmatic
               }

This does work on the websites I try (an admittedly very poor sample of less than a dozen websites).

I should note that I’m not doing security related code, so I am OK trusting the ContentType. I’m not trying to determine if someone is maliciously altering the headers.

The most obvious problem is I would think I am missing relatively common client side applications (I’m only testing for (x)html and javascript). Browsers and extensions might run python? jquery might not use application/javascript MIME type sometimes? I don’t know. (I’m not testing for java code, but am uncertain if that is an issue, without a java plugin).

Also, the above code seems pretty inefficient (faster try is below). Is there some function or library out there that will do this quicker? I searched in stackoverflow and generally googled but my searches aren’t finding anything.

More efficient code, but less accuracy could be a problem:

                string mimePrefix,mimeSuffix, mimeScript;
                if (null != context.HttpContext.Response.ContentType &&
                      context.HttpContext.Response.ContentType.Length >= 8)
                {
                    mimePrefix = context.HttpContext.Response.ContentType.Substring(0, 5); // "text/"
                    mimeSuffix = context.HttpContext.Response.ContentType.Substring(5, 3); // First three chars after "text/", so this would be "htm" for "text/html"
                    if (context.HttpContext.Response.ContentType.Length < 22) 
                        mimeScript = "";
                    else             // find "application/javascript" if present
                        mimeScript = context.HttpContext.Response.ContentType.Substring(0, 22);
                }
                else
                {
                    mimePrefix = mimeSuffix = mimeScript = "";
                }
                if ( context.HttpContext.Response.StatusCode < 400 &&
                     (
                        "text/" == mimePrefix && 
                          ("jav" == mimeSuffix || "htm" == mimeSuffix || 
                           "xml" == mimeSuffix)
                     ) 
                     || "application/javascript" == mimeScript
                   )
                { 
                       // Proceed with operations on replies that might be programmatic
                }

Again, just wondering if there is some function or library I should be using, or if there is a better coding algorithm that be more accurate or faster, or better in other ways.