Archives / 2005 / October

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  • Possible Bug : HttpPost and class name conflicts

    A colleague and friend of mine run into some very odd web service behaviour on ASP.NET 1.1. Anyone who can shed some light on this, please leave a comment. I have pasted his exact text describing the problem below.

    Included below is a minimal web-service implementation to recreate a problem
    I've encountered in a web service that has methods returning classes with the
    same local name (but in different namespaces).

    If only the SoapHttp protocol is enabled in the web.config, everything works
    as expected - with the different "Something" classes being serialized in to
    different XML namespaces as defined by the ResponseNamespace property of the
    SoapDocumentMethod attributes.

    However - if HttpPost or HttpPostLocalhost are enabled (the latter being
    enabled by default), and I browse to the asmx file in IE, I get this error :

    Types NsProblem.B.Something and NsProblem.A.Something both use the XML type
    name, Something, from namespace http://example/NsProblem/. Use XML attributes
    to specify a unique XML name and/or namespace for the type.

    If I un-comment both of the "XmlRoot" elements I get this error

    The XML element named 'Something' from namespace 'http://example/NsProblem/'
    references distinct types NsProblem.A.Something and NsProblem.B.Something.
    Use XML attributes to specify another XML name or namespace for the element
    or types.

    Now for the really strange bit : leave one XmlRoot attribute commented, and
    the other not, and it works!

    When it is working, the example responses (on whatever.asmx?op=GetArrayA)
    don't appear to tbe any difference!

    (aside: I also tried setting the responses to be different using Xml
    Serialization attributes, i.e. putting [return: XmlElement(... )] on the
    methods, but like the SoapDocumentMethod attribute this only seemed to change
    the response for the Soap method - making no difference to the HTTP POST

    Various workarounds are available
     - disable (remove) "HttpPost" and "HttpPostLocalhost" in web.config
     - Rename the classes (making the namespaces redundant)
    but I would prefer to be able to keep the class names as they are, and keep
    the HttpPostLocalhost enabled for testing / debugging purposes - and I
    anticipate needing to support 3 or more classes with the same local-name
    across different namespaces.

    ---- Minimal test case ----

    <%@ WebService Language="c#" Class="NsProblem.XmlTestSvc" %>
    using System;
    using System.Web.Services;
    using System.Web.Services.Protocols;
    using System.Xml.Serialization;

    namespace NsProblem.A
    //    [XmlRoot(Namespace="AAAA")]
        public class Something { }

    namespace NsProblem.B
    //    [XmlRoot(Namespace="BBBB")]
        public class Something { }

    namespace NsProblem
        [WebService(Description="Conflicting name problem example",
        public class XmlTestSvc : System.Web.Services.WebService
            public NsProblem.A.Something[] GetArrayA() { return null; }
            public NsProblem.B.Something[] GetArrayB() { return null; }