Web Request Utility

There are a couple of severe issues with your code so it won't work the way you think it would and you will also loose a lot of useful information.

ApplicationProvider.Log.Fatal($"Web request failed due to null value. {url}");
throw new Exception($"A null parameter or response has occurred for {url}");

These two lines will never be executed because the WebRequest.Create Method will throw the

ArgumentNullException if requestUriString is null.

This will happen before you can log it so you should validate the argument yourself with:

if (string.IsNullOrEmpty(url)) throw new ArgumentNullException(nameof(url));

In order to reduce nesting you should use early returns. This means that you should negate the first condition:

if (!(WebRequest.Create(url) is HttpWebRequest request))
{
    ...
}

in other places however you can use positive conditions (which are preferable because they are easier to understand) to further reduce nesting like where you check the stream:

if (stream == null)

Your method only throws Exceptions. This is always bad because the name of the exception is a very important information source for why it was thrown. If you don't want to reveal what really happened, or if you want to use a more generic exception the you should create your own type. But when you do it, don't leave the stack trace behind by not passing the previous exception as inner exception.

Without you providing more context, I find you code should optimally look like this:

• check the argument and throw early
• create a web-request and throw early if it wasn't what you'd expected
• try to get the stream an throw early if it's null
• if the HttpRequestException was thrown, log it and either rethrow with with simple throw; or throw you own exception passing the other one as parameter.

Example:

public object DownloadFromApi(string url)
{
    if (string.IsNullOrEmpty(url)) throw new ArgumentNullException(nameof(url));

    if (!(WebRequest.Create(url) is HttpWebRequest request))
    {
        ApplicationProvider.Log.Fatal($"Web request failed due to null value. {url}");
        throw new InvalidUrlException($"The provider url '{url}' is not a http-web-request url.");
    }

    request.Method = "GET";
    request.ContentType = "application/json";

    try
    {
        using (var response = (HttpWebResponse)request.GetResponse())
        using (var stream = response.GetResponseStream())
        {
            if (stream == null)
            {
                ApplicationProvider.Log.Fatal($"No response from {url}");
                throw new ResponseException($"No response from web server {url}");
            }

            using (var reader = new StreamReader(stream))
            {
                if (response.StatusCode == HttpStatusCode.OK)
                {
                    return JsonConvert.DeserializeObject(reader.ReadToEnd());                    
                }

                ApplicationProvider.Log.Error($"Failed Request with code of {response.StatusCode} at {url}");
            }
        }
    }
    catch (HttpRequestException innerException)
    {
        ApplicationProvider.Log.Fatal($"An unhandled HTTP error has occurred.{Environment.NewLine}{exception.Message}");
        throw new DownloadException(innerException);
    }
}

It's just an example. You can of course use other exception type that suit your needs but remember to not use the Exception, it's not helpful.