Web Method returns array of custom type : casting error

Web Method returns array of custom type : casting error

Post by John Grand » Fri, 25 Mar 2005 04:37:16


My ASP.NET Web Service project has a Web Method that returns an array filled
with instances of a custom class.

The custom class is defined in a Class Library that is included in the
web-service project.

The same class lib is included in the ASP.NET Web Application that calls the
web-method

I can successfully call the web-method with

object[] a = WebReference.WebService.WebMethod();

but when I attempt

myClass element = (myClass) a[i];

I receive the runtime error

"Specified cast is not valid."
 
 
 

Web Method returns array of custom type : casting error

Post by Manohar Ka » Fri, 25 Mar 2005 05:00:41

What the web method (actually the method from proxy class) is returning is a
proxy-type, and not the type that web service originally returned. You have
two choices:

1. Use the proxy type as-is. Since this was generated class, it will be
close to what the web service returned, sans any methods.

2. Manually edit the proxy class (found in webreferences folder of your web
site, with the same name as the reference page), and remove the proxy type,
and include the actual type in the cs file. Then add the corresponding using
statement as well.


--
Manohar Kamath
Editor, .netWire
www.dotnetwire.com




filled
the

 
 
 

Web Method returns array of custom type : casting error

Post by John Grand » Fri, 25 Mar 2005 06:14:42

Hi Manohar, and thanks for the response.

<<<
1. Use the proxy type as-is. Since this was generated class, it will be
close to what the web service returned, sans any methods.

My custom class is very simple. Two private fields. Two properties to
read-access the private fields. Two constructors (default, and one that
sets the two fields' values).

Are you saying that the proxy type will contain the data that my custom
class contains , but the two properties will not be available ?

So, I access the data like this:

a[i].Field1
a[i].Field2


<<<
2. Manually edit the proxy class (found in webreferences folder of your web
site, with the same name as the reference page), and remove the proxy type,
and include the actual type in the cs file. Then add the corresponding using
statement as well.

I'm not sure exactly what to do here.

Looking at my web-application in Visual Studio, and clicking on the
web-reference, a number of expandable nodes are shown: these appear to be
all of the types that my web-service references. Among them is listed the
name of my custom class -- but the first character is in lower case. In the
tree that expands from that node are listed my class' fields, construtors,
and properties exactly as I've defined them.

I'm looking at the contents of the "Web References" folder underneath my
web-app's physical folder: Reference.cs, Reference.map,
<web-service-name>.disco, <web-service-name>.wsdl

These files all look very dangerous to edit.
 
 
 

Web Method returns array of custom type : casting error

Post by Manohar Ka » Fri, 25 Mar 2005 07:32:50

am saying, your proxy type is identical to your custom type (almost),
except it will be in another namespace -- same as that of the proxy class.
So, by doing a manual changes, you are tricking SOAP to think that it is
actually deserializing to proxy type. As long as the names and types are
same, it will work.

--
Manohar Kamath
Editor, .netWire
www.dotnetwire.com


"John Grandy" <johnagrandy-at-yahoo-dot-com> wrote in message
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web
type,
using
the
is
calls


 
 
 

Web Method returns array of custom type : casting error

Post by John Grand » Fri, 25 Mar 2005 07:51:17

k. I edited Reference.cs so that my custom type is explicitly declared
using the class library namespace:

used to be : public MyCustomClass Method1() {

changed to: public MyCustomClassLibrary.MyCustomClass Method1() {


Now what happens is that I receive no compile-time nor run-time errors, but
on the web-app side, properties of an instance of MyCustomClass are always
null, no matter what values MyWebService.Method1() has set them to.


so ...

object[] array = MyWebReference.Method1();
(MyCustomClass) element = array[0];
String s1 = element.Field1;
String s2 = element.Field2;

element.Field1 and element.Field2 are always null,



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Web Method returns array of custom type : casting error

Post by Manohar Ka » Fri, 25 Mar 2005 07:57:52

think you misunderstood me...

In the reference.cs, DELETE the custom type MyCustomClass. Then, add the
using statement with the namespace MyCustomClassLibrary. You should not have
to change anything else.


--
Manohar Kamath
Editor, .netWire
www.dotnetwire.com


"John Grandy" <johnagrandy-at-yahoo-dot-com> wrote in message
news:e1s6Tr$ XXXX@XXXXX.COM ...
but
class.
are
that
be
In
my
returning
You
be
your
corresponding
array
the


 
 
 

Web Method returns array of custom type : casting error

Post by John Grand » Fri, 25 Mar 2005 08:30:01

hh, I see. The problem is that the MyCustomClass stub in References.cs
causes the compiler to think that web-method return types of MyCustomClass
originate in the web-service rather than in MyCustomClassLibrary.

Correct ?

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Web Method returns array of custom type : casting error

Post by Manohar Ka » Fri, 25 Mar 2005 10:13:32

es... by removing the custom type, you are actually returning from the
proxy class, an object which is the same type the web service returns.

--
Manohar Kamath
Editor, .netWire
www.dotnetwire.com


"John Grandy" <johnagrandy-at-yahoo-dot-com> wrote in message
news: XXXX@XXXXX.COM ...
(almost),
proxy
corresponding
to
listed
underneath
will
in
that