I've been poking around the web for a couple of hours trying to find an answer to this one.  I'm in the process of building a web service for one of our clients.  It uses cookieless sessions, so the client needs a way get the redirected URL containing the session id.  They would like to do this with a HEAD request. For some reason, I can't get this to work in my test client.  Here's my code:

        Dim req As System.Net.HttpWebRequest = System.Net.WebRequest.Create("http://localhost/webserv/webserv.asmx/Ping")
        With req
            .Method = "HEAD"
            .Timeout = 20000
        End With
        Dim res As System.Net.HttpWebResponse = req.GetResponse
        txtAnswer.Text = res.ResponseUri.AbsoluteUri
        res.Close()

Submitting this results in the "(500) Internal Server Error" on the line that calls GetResponse.  If I change the Method to "GET", it works, returning the response url.  The Ping method above is an empty Sub so there's no code in there to fail.

I've also discovered that if I remove the method from the URL leaving http://localhost/webserv/webserv.asmx, I get the "(405) Method Not Allowed" error.

Is it possible to perform a HEAD request against a web service?  Do I need to do something in the web service or IIS config?  This is running on an older machine (IIS 5.0).  Any help would be much appreciated.

ck

Please post some code from the web service. If you can't post your actual code, then try this with a "hello, world" service, and post the code to that.

Please don't make us guess. You're going to get much better answers if the people answering don't have to guess.

Hey John, thanks for the tip.  I've gone ahead and created a new web service, WebService1, containing the HelloWorld method.  The only change I made was to enable sessions so the code looks like this:

Imports System.Web.Services
Imports System.Web.Services.Protocols
Imports System.ComponentModel

<System.Web.Services.WebService(Namespace:="http://tempuri.org/")> _
<System.Web.Services.WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
<ToolboxItem(False)> _
Public Class WebService1
    Inherits System.Web.Services.WebService

    <WebMethod(EnableSession:=True)> _
    Public Function HelloWorld() As String
        Return "Hello World"
    End Function

End Class

I recompiled the web service and updated my client code to use the new service/method.

    Protected Sub btnTest_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnTest.Click
        Dim req As System.Net.HttpWebRequest = System.Net.WebRequest.Create("http://localhost:54303/ECTools/WebService1.asmx/HelloWorld")
        With req
            .Method = "HEAD"
            .Timeout = 20000
        End With
        Dim res As System.Net.HttpWebResponse = req.GetResponse
        txtAnswer.Text = res.ResponseUri.AbsoluteUri
        res.Close()
    End Sub

Still experiencing the same behavior.  Thanks.

Excellent. Now, take a look in the Application event log on the server to see if ASP.NET has entered any indication of the reason for the server error.

I'll go ahead and post the contents of the warning: 

Event code: 3005 
Event message: An unhandled exception has occurred. 
Event time: 7/6/2009 9:03:53 AM 
Event time (UTC): 7/6/2009 1:03:53 PM 
Event ID: 94d32036ad5a4baaa9a357fe7d59bddd 
Event sequence: 93 
Event occurrence: 8 
Event detail code: 0 
 
Application information: 
    Application domain: /LM/W3SVC/3/Root-97-128910392467973398 
    Trust level: Full 
    Application Virtual Path: / 
    Application Path: C:\Development_Web_Sites\ZZCOMOP\ 
    Machine name: TEST 
 
Process information: 
    Process ID: 2872 
    Process name: aspnet_wp.exe 
    Account name: TEST\ASPNET 
 
Exception information: 
    Exception type: WebException 
    Exception message: The remote server returned an error: (500) Internal Server Error. 
 
Request information: 
    Request URL: http://localhost:54302/ECToolsApp.aspx 
    Request path: /ECToolsApp.aspx 
    User host address: 172.16.10.110 
    User:  
    Is authenticated: False 
    Authentication Type:  
    Thread account name: TEST\ASPNET 
 
Thread information: 
    Thread ID: 5 
    Thread account name: TEST\ASPNET 
    Is impersonating: False 
    Stack trace:    at System.Net.HttpWebRequest.GetResponse()
   at ECToolsApp.btnTest_Click(Object sender, EventArgs e) in C:\Development_Web_Sites\ZZCOMOP\ECToolsApp.aspx.vb:line 176
   at System.Web.UI.WebControls.Button.OnClick(EventArgs e)
   at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument)
   at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
   at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
   at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
 
 
Custom event details: 
 

There were no custom details.  The error is occurring when I try to call GetResponse with the Method set to HEAD.

Sorry, I meant on the server running the web service.

Server error 500 is from the server. It usually means that there was an unhandled exception.

Ah, I see...  The web service and test client are actually running on the same server.  I didn't notice before that each request was generating two errors.  Here's the details on the web service error:

Event code: 3005 
Event message: An unhandled exception has occurred. 
Event time: 7/6/2009 9:03:53 AM 
Event time (UTC): 7/6/2009 1:03:53 PM 
Event ID: 90d1822f05ac44b888c3566d939865de 
Event sequence: 15 
Event occurrence: 2 
Event detail code: 0 
 
Application information: 
    Application domain: /LM/W3SVC/4/Root/ECTools-98-128913583052484232 
    Trust level: Full 
    Application Virtual Path: /ECTools 
    Application Path: C:\Development_Web_Sites\ZZCOMPCLT\ECTools\ECTools\ 
    Machine name: TEST 
 
Process information: 
    Process ID: 2872 
    Process name: aspnet_wp.exe 
    Account name: TEST\ASPNET 
 
Exception information: 
    Exception type: InvalidOperationException 
    Exception message: Request format is unrecognized for URL unexpectedly ending in '/HelloWorld'. 
 
Request information: 
    Request URL: http://localhost:54303/ECTools/WebService1.asmx/HelloWorld 
    Request path: /ECTools/WebService1.asmx/HelloWorld 
    User host address: 172.16.10.228 
    User:  
    Is authenticated: False 
    Authentication Type:  
    Thread account name: TEST\ASPNET 
 
Thread information: 
    Thread ID: 14 
    Thread account name: TEST\ASPNET 
    Is impersonating: False 
    Stack trace:    at System.Web.Services.Protocols.WebServiceHandlerFactory.CoreGetHandler(Type type, HttpContext context, HttpRequest request, HttpResponse response)
   at System.Web.Services.Protocols.WebServiceHandlerFactory.GetHandler(HttpContext context, String verb, String url, String filePath)
   at System.Web.HttpApplication.MapHttpHandler(HttpContext context, String requestType, VirtualPath path, String pathTranslated, Boolean useAppConfig)
   at System.Web.HttpApplication.MapHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)
 
 
Custom event details: 

Is the web server trying to process the request as a GET even though the Method is set to HEAD?  Does my request have to be something other than an HttpWebRequest?  Or maybe I should be calling something other than GetResponse.  I'm going to try some things along these lines, but if you have any ideas, please let me know.

I'm very sorry I didn't notice before. I guess I thought since you were using HEAD, that you were using an AJAX-style service.

You're just using a plain, old, (legacy) ASMX service, which supports SOAP and maybe GET and POST. And nothing else.

Sorry. Can't happen, at least not with (legacy) ASMX services (See ASMX Web Services are a “Legacy Technology”).

However, this does work in WCF.