<p>Apparently you can easily obtain a client IP address in WCF 3.5 but not in WCF 3.0.  Anyone know how?</p>

This doesn't help you in 3.0, but I can just see people finding this question and being frustrated because they are trying to get the client IP address in 3.5. So, here's some code which should work:
```
```
using System.ServiceModel;
using System.ServiceModel.Channels;

OperationContext context = OperationContext.Current;
MessageProperties prop = context.IncomingMessageProperties;
RemoteEndpointMessageProperty endpoint =
    prop[RemoteEndpointMessageProperty.Name] as RemoteEndpointMessageProperty;
string ip = endpoint.Address;
```
```