Redirect Non WWW to WWW [duplicate] - asp.net-core

Question

This question already has answers here:
Redirect Non WWW to WWW using Asp.Net Core Middleware
(10 answers)
Closed 4 years ago.
On an ASP.Net Core application startup I have:
RewriteOptions rewriteOptions = new RewriteOptions();
rewriteOptions.AddRedirectToHttps();
applicationBuilder.UseRewriter(rewriteOptions);
When in Production I need to redirect all Non WWW to WWW.
For example:
domain.com/contact > www.domain.com/contact
How can I do this using Rewrite Middleware?

Answer 1

You could create a custom rule by creating a class and implementing the IRule interface (see below). I think there must be a better way to construct the redirectUrl though.
public class CanonicalDomainRewriteRule : IRule
{
public void ApplyRule(RewriteContext context)
{
HttpRequest request = context.HttpContext.Request;
if (request.Host.Value.StartsWith("www.", StringComparison.OrdinalIgnoreCase))
{
return;
}
else
{
HttpResponse response = context.HttpContext.Response;
string redirectUrl = $"{request.Scheme}://www.{request.Host}{request.Path}{request.QueryString}";
response.Headers[HeaderNames.Location] = redirectUrl;
response.StatusCode = StatusCodes.Status301MovedPermanently;
context.Result = RuleResult.EndResponse;
}
}
}
You can add this rule as follows in your ConfigureServices method:
RewriteOptions rewriteOptions = new RewriteOptions()
.Add(new CanonicalDomainRewriteRule());
app.UseRewriter(rewriteOptions);
See Extensions and Options: IRule-based rule for further examples.