Arrays of structs are not supported with encoded SOAP

[SB]

I have few web service methods that take and return array of structures. I
created these web methods in .NET with the default encoding
(document/literal). They worked perfectly during my testing.
Later I had to comply with one of the requirements from the customer and
made the web service to use rpc/literal encoding and used the [SoapRpcMethod]
attribute. It compiles and builds without any trobule. But when I try to add
web reference to this service, it comes with exceptions and the message
'Cannot serialize Abc.Xyz.CustomerKey[], Arrays of structs are not supported
with encoded SOAP' and a full exception stack trace.

This is my sample structure:

public struct CustomerKey
{
public string Name;
public string Id;
}

This is my sample web method defintion:
[WebMethod]
[SoapRpcMethod]
public int GetOrderCount(CustomerKey[] customerKeys)
{
....
}

I tried adding a [Serializable] attribute to the struct and has no effect.
But if I changed the struct to a class it works fine.

Please advise me if I am missing any important stuff here or the proper way
of dealing with this issue.

Regards,
SB