Broken encoding after postback

I have a query string with a parameter value that contains the norwegian character å encoded as %e5. The page contains a form with an action attribute which is automatically filled by ASP.Net. When the URL is output into said attribute it is printed with a full two byte encoding: %u00e5.

When posting back this seems to be ok when debugging the code behind. However the page actually does a redirect to itself (for some other reason) and the redirect location header looks like this: Location: /myFolder/MyPage.aspx?Param1=%C3%A5

So the %e5 has been translated to %C3%A5 which breaks the output somehow.

In HTML text the broken characters look like &开发者_如何学Go;#195;¥ after having been output via HttpUtility.HtmlEncode.

The entire web application is ISO8859-1 encoded.

PS. When removing the u00 from the output %u00e5 in the action attribute before posting the form, everything is output nicely. But the error seems to be the translation from %e5 to %C3%A5. (And of course the self redirect, but that's another matter.)

Any pointers?

The solution I ended up with was encoding the redirect URL manually.

public void ReloadPage()
{
    UrlBuilder url = new UrlBuilder(Context, Request.Path);
    foreach (string queryParam in Request.QueryString.AllKeys)
    {
        string queryParamValue = Request.QueryString[queryParam];
        url.AddQueryItem(queryParam, queryParamValue);
    }
    Response.Redirect( url.ToString(), true);
}

The url.AddQueryItem basically does HttpContext.Server.UrlDecode(queryParamValue) and the url.ToString builds the query string and for each query item does HttpContext.Server.UrlEncode( queryParamValue).

The UrlBuilder is a class already present in our library, so once I found the problem and realized that C#/.Net didn't provide tools for this, coding the fix was quick :)