To set up the target in the configuration file, use the following syntax:

<nlog autoReload="true" xmlns="http://www.nlog-project.org/schemas/NLog.xsd" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> 
  <targets> 
    <target name="ws" xsi:type="WebService" 
            namespace="http://www.nlog-project.org/example" protocol="Soap11" 
            methodName="HelloWorld" url="http://localhost:2648/Service1.asmx"> 
      <parameter name="n1" type="System.String" layout="${message}"/> 
      <parameter name="n2" type="System.String" layout="${logger}"/> 
      <parameter name="n3" type="System.String" layout="${level}"/> 
    </target> 
  </targets> 
  <rules> 
    <logger name="*" writeTo="ws"/> 
  </rules> 
</nlog> 

This assumes just one target and a single rule. More configuration options are described here.

To set up the log target programmatically use code like this:

using NLog; 
using NLog.Targets; 
 
class Example 
{ 
    static void Main(string[] args) 
    { 
        WebServiceTarget target = new WebServiceTarget(); 
        target.Url = "http://localhost:2648/Service1.asmx"; 
        target.MethodName = "HelloWorld"; 
        target.Namespace = "http://www.nlog-project.org/example"; 
        target.Protocol = WebServiceTarget.WebServiceProtocol.Soap11; 
 
        target.Parameters.Add(new MethodCallParameter("n1", "${message}")); 
        target.Parameters.Add(new MethodCallParameter("n2", "${logger}")); 
        target.Parameters.Add(new MethodCallParameter("n3", "${level}")); 
 
        NLog.Config.SimpleConfigurator.ConfigureForTargetLogging(target, LogLevel.Debug); 
 
        Logger logger = LogManager.GetLogger("Example"); 
        logger.Trace("log message 1"); 
        logger.Debug("log message 2"); 
        logger.Info("log message 3"); 
        logger.Warn("log message 4"); 
        logger.Error("log message 5"); 
        logger.Fatal("log message 6"); 
    } 
}

The example web service that works with this example is shown below

using System; 
using System.Data; 
using System.Web; 
using System.Collections; 
using System.Web.Services; 
using System.Web.Services.Protocols; 
using System.ComponentModel; 
 
namespace WebService1 
{ 
    [WebService(Namespace = "http://www.nlog-project.org/example")] 
    [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] 
    [ToolboxItem(false)] 
    public class Service1 : System.Web.Services.WebService 
    { 
        [WebMethod] 
        public void HelloWorld(string n1, string n2, string n3) 
        { 
            HttpContext.Current.Trace.Write("n1 " + n1); 
            HttpContext.Current.Trace.Write("n2 " + n2); 
            HttpContext.Current.Trace.Write("n3 " + n3); 
        } 
    } 
}