WCF Tracing in ASP.NET Core

In case of client side tracing I used custom endpoint behaviour (IEndpointBehavior) with custom message logging inspector (IClientMessageInspector) to get input and output messages.

Client initialization:

_serviceClient = new MyCustomServiceClient();
_serviceClient.Endpoint.Address = new System.ServiceModel.EndpointAddress(_configParams.ServiceUri);
_serviceClient.Endpoint.EndpointBehaviors.Add(new EndpointLoggingBehavior("MyCustomService"));

Implementation of EndpointLoggingBehavior:

public class EndpointLoggingBehavior : IEndpointBehavior
    {
        public EndpointLoggingBehavior(string serviceName)
        {
            _serviceName = serviceName;
        }

        private readonly string _serviceName;

        public void AddBindingParameters(ServiceEndpoint endpoint,
            System.ServiceModel.Channels.BindingParameterCollection bindingParameters)
        {
        }

        public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
        {
            clientRuntime.ClientMessageInspectors.Add(new MessageLoggingInspector(_serviceName));
        }

        public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
        {
        }

        public void Validate(ServiceEndpoint endpoint)
        {
        }
    }

Implementation of MessageLoggingInspector:

public class MessageLoggingInspector : IClientMessageInspector
    {
        private readonly string _serviceName;
        public MessageLoggingInspector(string serviceName)
        {
            _serviceName = serviceName;
        }
        public void AfterReceiveReply(ref Message reply, object correlationState)
        {
            // copying message to buffer to avoid accidental corruption
            var buffer = reply.CreateBufferedCopy(int.MaxValue);
            reply = buffer.CreateMessage();
            // creating copy
            var copy = buffer.CreateMessage();
            //getting full input message
            var fullInputMessage = copy.ToString();

        }
        public object BeforeSendRequest(ref Message request, IClientChannel channel)
        {
            // copying message to buffer to avoid accidental corruption
            var buffer = request.CreateBufferedCopy(int.MaxValue);
            request = buffer.CreateMessage();
            // creating copy
            var copy = buffer.CreateMessage();
            //getting full output message
            var fullOutputMessage = copy.ToString();
            return null;
        }
    }

Then, of course, you will need to write these messages to any storage.

You'll use ETW Tracing for WCF on .NET Core

https://github.com/dotnet/wcf/blob/master/Documentation/HowToUseETW.md

In my experience, you have some limitations

1. Tracing is on for All WCF Apps, rather than configuring for a single app through config file
2. You cannot output Messages with ETW tracing
3. SvcTraceViewer.exe doesn't work well for trace review, you'll need to move to PerfView.exe which may present a learning curve

Benefits of ETW

1. You avoid the performance hit from classic forms of tracing
2. No more config change to start/stop tracing

Building on the excellent answer by Petr Pokrovskiy, this is how you can redirect the trace to the standard .NET Core log:

Client initialization:

ILogger<MyCustomService> = ...; // use dependency injection to get instance
_serviceClient = new MyCustomServiceClient();
_serviceClient.Endpoint.Address = new System.ServiceModel.EndpointAddress(_configParams.ServiceUri);
_serviceClient.Endpoint.SetTraceLogging(logger);

Implementation of SetTraceLogging:

using Microsoft.Extensions.Logging;
using System;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.ServiceModel.Description;
using System.ServiceModel.Dispatcher;

namespace Common.ServiceModel.Logging
{
    public static class ServiceEndpointExtensions
    {
        public static void SetTraceLogging(this ServiceEndpoint serviceEndpoint, ILogger logger)
        {
            if (logger == null)
                throw new ArgumentNullException(nameof(logger));
            if (logger.IsEnabled(LogLevel.Trace))
                serviceEndpoint.EndpointBehaviors.Add(new ClientMessageLoggingBehavior(logger));
        }
    }

    internal sealed class ClientMessageLoggingBehavior :
        IEndpointBehavior
    {
        private readonly ILogger _logger;

        public ClientMessageLoggingBehavior(ILogger logger)
        {
            _logger = logger;
        }

        public void AddBindingParameters(ServiceEndpoint endpoint, BindingParameterCollection bindingParameters)
        {
        }

        public void ApplyClientBehavior(ServiceEndpoint endpoint, ClientRuntime clientRuntime)
        {
            clientRuntime.ClientMessageInspectors.Add(new ClientMessageLogger(_logger));
        }

        public void ApplyDispatchBehavior(ServiceEndpoint endpoint, EndpointDispatcher endpointDispatcher)
        {
        }

        public void Validate(ServiceEndpoint endpoint)
        {
        }
    }

    internal sealed class ClientMessageLogger :
        IClientMessageInspector
    {
        private readonly ILogger _logger;

        public ClientMessageLogger(ILogger logger)
        {
            this._logger = logger;
        }

        public void AfterReceiveReply(ref Message reply, object correlationState)
        {
            // copying message to buffer to avoid accidental corruption
            reply = Clone(reply);
            this._logger.LogTrace("Received SOAP reply:\r\n{0}", reply.ToString());

        }

        public object BeforeSendRequest(ref Message request, IClientChannel channel)
        {
            // copying message to buffer to avoid accidental corruption
            request = Clone(request);
            this._logger.LogTrace("Sending SOAP request:\r\n{0}", request.ToString());
            return null;
        }

        private static Message Clone(Message message)
        {
            return message.CreateBufferedCopy(int.MaxValue).CreateMessage();
        }
    }
}