HttpContext.Current.Request和Page.Request中的Url.Host

Question

I have following method:

    public static string GetHttpHost(System.Web.HttpRequest hr)
    {
        return "http://" + hr.Url.Host + ":" + hr.Url.Port.ToString() ;
    }

When I call this method with GetHttpHost(this.Request) and GetHttpHost(HttpContext.Current.Request) , it returns different results.

For example:

• My request page is http://192.168.1.103/mypage.aspx
• In mypage.aspx.cs, calling GetHttpHost(this.Request) returns http://192.168.1.103:80
• When rendering mypage.aspx, some biz logic is involved, so BLL.dll is loaded. In BLL.dll, calling GetHttpHost(HttpContext.Current.Request) returns http://app133:80 (app133 is our web server's name)

I searched in Stack Overflow, all related questions tell me that HttpContext.Current.Request and Page.Request are same object.

So, can anyone tell me what happened in my code?

Thanks.

Answer 1

No, HttpContext.Current.Request and Page.Request are not the same. Both are instances of the same class (HttpRequest) but those are different instances.

In each case, the private HttpRequest instance is created differently - I could not find the exact code creating it but keep in mind that HttpContext.Current is created only once, long before any Page.

It all boils down to the following code in HttpRequest class:

public Uri Url
{
    get
    {
        if (this._url == null && this._wr != null)
        {
            string text = this.QueryStringText;
            if (!string.IsNullOrEmpty(text))
            {
                text = "?" + HttpUtility.CollapsePercentUFromStringInternal(text, this.QueryStringEncoding);
            }
            if (AppSettings.UseHostHeaderForRequestUrl)
            {
                string knownRequestHeader = this._wr.GetKnownRequestHeader(28);
                try
                {
                    if (!string.IsNullOrEmpty(knownRequestHeader))
                    {
                        this._url = new Uri(string.Concat(new string[]
                        {
                            this._wr.GetProtocol(), 
                            "://", 
                            knownRequestHeader, 
                            this.Path, 
                            text
                        }));
                    }
                }
                catch (UriFormatException)
                {
                }
            }
            if (this._url == null)
            {
                string text2 = this._wr.GetServerName();
                if (text2.IndexOf(':') >= 0 && text2[0] != '[')
                {
                    text2 = "[" + text2 + "]";
                }
                this._url = new Uri(string.Concat(new string[]
                {
                    this._wr.GetProtocol(), 
                    "://", 
                    text2, 
                    ":", 
                    this._wr.GetLocalPortAsString(), 
                    this.Path, 
                    text
                }));
            }
        }
        return this._url;
    }
}

As you can see, it first tries to read known request header ( GetKnownRequestHeader method in System.Web.HttpWorkerRequest base class) and only if it fails it will invoke GetServerName method which will return either IP address or server name depending where the web application is hosted.

Didn't find any official documentation or proof as to why exactly one returns IP and other the machine name, but the above can explain the difference.