Question

We have an existing application for which one of our DTO object has a property typed as IDictionary<string, object>.

I am now trying to expose this object through a WCF service. This works in some cases, but not in the general case. To demonstrate the problem, consider the following two methods:

[OperationContract]
public IDictionary<string, object> Test1()
{
    return new Dictionary<string, object>
    {
        { "testkey1", "newstringvalue"},
    };
}

[OperationContract]
public IDictionary<string, object> Test2()
{
    return new Dictionary<string, object>
    {
        { "testkey1", "newstringvalue"},
        { "testkey2", new object [] { "one" , "two", "three", } }
    };
}

Method Test1() works as expected, but when I call Test2(), I get a strange runtime error on the client:

The request channel timed out while
waiting for a reply after 00:01:00.
Increase the timeout value passed to
the call to Request or increase the
SendTimeout value on the Binding. The
time allotted to this operation may
have been a portion of a longer
timeout.

Inner exception: The remote server
returned an error: (504) Gateway
Timeout.

This is despite the fact that the exception was thrown instantly, ie. I didn’t actually have to wait a minute for this response. No error is shown on the server.

I suspect this stems from the fact that the serializer can’t serialize object[], but this is not what is indicated by the error.

So my questions are:

1. What is going on here?
2. How do I work around this so I can serialize my objects correctly?

Thanks.

Answer 1

As neither myself or any of my colleagues could think of a way to make this serialization work directly, we worked around the issue in the end by wrapping our object in a custom object, which converts the Dictionary<string, object> to a Dictionary<string, string>, which has a special serialization case defined for string arrays. We then changed the application to be aware of this. Not particularly elegant, but simple enough, and seems to work.