Changing the scheme of System.Uri

I'm looking for canonical way of changing scheme of a given System.Uri instance with System.UriBuilder without crappy string manipulations and magic constants. Say I have

var uri = new Uri("http://localhost/hello")

and I need to change it to 'https'. My issue is in limited UriBuilder ctors and Uri.Port defaulting to 80 (should we change it to 443? hardcoding?). The code must respect all Uri properties such as possible basic auth credentials, query string, etc.

Ended up with this one:

var uriBuilder = new UriBuilder(requestUrl)
{
	Scheme = Uri.UriSchemeHttps,
	Port = -1 // default port for scheme
};

UserControl's answer works fine unless you have to make sure non-default ports are preserved in the URI.

For instance, http://localhost:12345/hello should become https://localhost:12345/hello instead of https://localhost/hello.

Here's how to do that easily:

public static string ForceHttps(string requestUrl)
{
    var uri = new UriBuilder(requestUrl);

    var hadDefaultPort = uri.Uri.IsDefaultPort;
    uri.Scheme = Uri.UriSchemeHttps;
    uri.Port = hadDefaultPort ? -1 : uri.Port;

    return uri.ToString();
}

Note that we have to read uri.Uri.IsDefaultPort before setting uri.Scheme.

Here is a working example: https://dotnetfiddle.net/pDrF7s

Another iteration on Good Night Nerd Pride's answer, as an extension:

public static Uri RewriteHttps(this Uri originalUri)
{
    return new UriBuilder(originalUri)
    {
        Scheme = Uri.UriSchemeHttps,
        Port = originalUri.IsDefaultPort ? -1 : originalUri.Port // -1 => default port for scheme
    }.Uri;
}

I prefer to pass the desired https port number into the ForceHttps method if you want to use a custom one otherwise omit the https port or use -1 to use the standard one (implicitly). I don't really bother with the port that is already on the url because http and https can never use the same port on the same server.

In the event that the url is already https, it will pass through unchanged leaving whatever port is there in place.

private static string ForceHttps(string requestUrl, int? httpsPort = null)
{
    var uri = new UriBuilder(requestUrl);
    // Handle https: let the httpsPort value override existing port if specified
    if (uri.Uri.Scheme.Equals(Uri.UriSchemeHttps)) {
        if (httpsPort.HasValue)
            uri.Port = httpsPort.Value;
        return uri.Uri.AbsoluteUri;
    }

    // Handle http: override the scheme and use either the specified https port or the default https port
    uri.Scheme = Uri.UriSchemeHttps;
    uri.Port = httpsPort.HasValue ? httpsPort.Value : -1;

    return uri.Uri.AbsoluteUri;
}

Usage:

ForceHttps("http://www.google.com/"); // https://www.google.com/
ForceHttps("http://www.google.com/", 225); // https://www.google.com:225/
ForceHttps("http://www.google.com/", 443); // https://www.google.com:443/
ForceHttps("https://www.google.com/"); // https://www.google.com/
ForceHttps("https://www.google.com:443/"); // https://www.google.com:443/
ForceHttps("https://www.google.com:443/", -1); // https://www.google.com/
ForceHttps("http://www.google.com:80/"); // https://www.google.com/
ForceHttps("http://www.google.com:3000/", 8080); // https://www.google.com:8080/