asp.net c# redirecting from http to https

I'd do a !Request.IsLocal as well to make sure that I'm not debugging, though if you're using a real instance of IIS with a cert applied when debugging that shouldn't be an issue.

if (!Request.IsLocal && !Request.IsSecureConnection)
{
    string redirectUrl = Request.Url.ToString().Replace("http:", "https:");
    Response.Redirect(redirectUrl, false);
    HttpContext.ApplicationInstance.CompleteRequest();
}

Note: This answer assumes an MVC context within a Controller where HttpContext is a property holding the current context. If you're unlucky enough to still be using WebForms or are referencing the context in a degenerate way you will need to use HttpContext.Current.ApplicationInstance.CompleteRequest().

Note: I've updated this to be consistent with the recommended pattern to terminate the request according to the framework documentation.

When you use this method in a page handler to terminate a request for one page and start a new request for another page, set endResponse to false and then call the CompleteRequest method. If you specify true for the endResponse parameter, this method calls the End method for the original request, which throws a ThreadAbortException exception when it completes. This exception has a detrimental effect on Web application performance, which is why passing false for the endResponse parameter is recommended. For more information, see the End method.

I usually call the following from the OnPreInit in a base class that all my pages inherit from. Of course, you could just do this in every page...but you wouldn't want to do that now would you?

Note that I've got two properties for each page so that I can specify the SSL requirement for each page (RequiresSSL) while I can also override and redirect check if I want (with IgnoreRequiresSSL, which is helpful for pages like error pages that you rewrite to and don't know whether they'll be encrypted or not), but of course, you can remove these for simple setups.

    protected override void OnPreInit(EventArgs e)
    {
        base.OnPreInit(e);

        if (!IsPostBack)
            RedirectAccordingToRequiresSSL();

        ...
    }

    /// <summary>
    /// Redirect if necessary to ssl or non-ssl enabled URL dependant on RequiresSSL property setting.
    /// </summary>
    private void RedirectAccordingToRequiresSSL()
    {
        if (IgnoreRequiresSSL) return;

        if (RequiresSSL)
        {
            if (!Request.IsSecureConnection) // Need to redirect to https
                RedirectAccordingToRequiresSSL(Uri.UriSchemeHttps);
        }
        else if (Request.IsSecureConnection)
        {
            RedirectAccordingToRequiresSSL(Uri.UriSchemeHttp);
        }

        // Otherwise don't need to do any redirecting as already using the correct scheme
    }

    /// <summary>
    /// Redirect as requested to specified scheme
    /// </summary>
    /// <param name="scheme"></param>
    private void RedirectAccordingToRequiresSSL(string scheme)
    {
        var url = scheme + Uri.SchemeDelimiter + Request.Url.Authority + Request.Url.PathAndQuery;
        Response.Redirect(url, false);
    }

In my opinion the following is the best all-round approach.

Three reasons

1. It works for both MVC and Web API as it is done at IIS level.
2. It does not effect local / debug settings. (permanent redirect can mess you around when debugging non https sites on your pc).
3. Uses a permanent redirect, so all future requests will automatically go to https

Simply add the following to your <system.webServer> section in your 'Web.config' for your project.

 <system.webServer>
 ....

 <rewrite>
  <rules>
    <rule name="HTTP to HTTPS redirect" stopProcessing="true">
      <match url="(.*)" />
      <conditions>
        <add input="{HTTP_HOST}" pattern="localhost" negate="true" />
        <add input="{HTTPS}" pattern="off" ignoreCase="true" />
      </conditions>
      <action type="Redirect" url="https://{HTTP_HOST}/{R:1}" redirectType="Permanent" />
    </rule>
  </rules>
  <outboundRules>
    <rule name="Add Strict-Transport-Security when HTTPS" enabled="true">
      <match serverVariable="RESPONSE_Strict_Transport_Security" pattern=".*" />
      <conditions>
        <add input="{HTTPS}" pattern="on" ignoreCase="true" />
      </conditions>
      <action type="Rewrite" value="max-age=31536000" />
    </rule>
  </outboundRules>
</rewrite>
</system.webServer>