VB6 software consuming WCF web services. Endpoints in App.config. Err VB6 has no App.config

We have an EPOS system that is built in VB6. A client is using Microsoft Dynamics AX as a CRM system. A 3rd party has created the AX implementation for our client and they've exposed a set of WCF web services that we need to consume to synchronise data between the EPOS and the AX CRM. Knowing VB6 would have issues calling WCF services, I created the following components to handle the communication between the EPOS and the AX CRM.

VB6 EPOS which calls -->

1) VB6 DLL wrapper which calls... -->

2) .NET(3.5) COM Callable Proxy DLL wrapper which calls... -->

3) .NET(3.5) Web Service Handler (Where the web servicesw actually get called) -->

Microsoft Dynamics AX CRM.

I built a test console app in Vb.NET to simulate calls from VB6 to help with debugging, so that test console app calls component 2.

Whilst doing this I was getting the following exception:-

"(could not find default endpoint element that references contract 'X' in the servicemodel client configuration section. this might be because no configuration file was found for your application, or because no endpoint element matching this contract could be found in the client element.)"

I googled around and found that I had to copy the bindings and endpoints section from Component 3's app.config to a new app.config for my Test Console app. I don't know WCF and haven't got the time at the moment, to really learn it to the point where I understand why this fixed this error.

Now though, I'm trying to call the services from the VB6 EPOS and this error is popping up again. So I added an app.config to Component 2, thinking that as Component 2 is the first .NET(3.5) component in the chain, that is where the endpoint declaration should go, but No. The error is still popping up.

Does anyone have any ideas? Any programming heroes out there that can shed some light on this for a simpleton please??? Please don't ask why we don't re-write the EPOS. We will. just not yet. Theres over 3 million lines of spaghetti code in there and I've only been working on it for 8 months!!!

As an aside, Doesn't this scenario break one of the golden rules of OOP, i.e. encapsulation. Why should my VB6 EPOS need to know what endpoints Component 3 us开发者_如何学JAVAes to access the WCF service???

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Great question here...

Your problem is essentially coming from all the required configuration data needed to work with a WCF Service.

When dealing with .NET Windows or Web Applications the configuration data on both the client and server sides of WCF Services reside in the application configuration file. For a windows application this file will be app.config, whereas it will be a web.config for a web application.

In your case, you would like to put the proxy logic in some form of a COM-visible .dll.

This is going to cause you some grief...in the .NET platform, the .config file for top-level host application (web or windows) is the place where all configuration data is read. Even if your application leverages dozens of .NET assemblies (each with custom configuration needs), the runtime is going to expect those configuration elements to all reside in the top-most application configuration file.

To resolve your issue, you are going to need to communicate to a service that VB6 does have access to (think ASMX web services) and have that service forward your call along to the appropriate WCF service.

The other alternative is to pass configuration variables directly from your VB6 application to your Com-visible assembly so you can use the extensibility model of WCF to create proxies (overriding the default behavior to read configuration data from a file) with your passed-in configuration.

I would say that the latter scenario could go both ways as far as being a violation of SOA/OOP..depending on the situation it may/may not be appropriate for the VB6 application to know about/store configuration details for communicating with the (eventual) WCF endpoint