How to protect the credential information in a WCF client?

I'm writing a desktop application that calls APIs of a WCF service. I used the "Add service reference..." option in Visual Studio and generate the proxy class in C#. Then I'll create an object of this C# class and set credential information for this object. However, the .NET code can easily be decompiled with tools like "Reflector", so my credential information will be disclosed. Is there any good way to protect my credential information? Maybe it is better to generate the proxy class in unmanaged code?