Given config

Workaround

Tool driven

Manual

<ItemGroup>       <ContentUpdate="Nlog.config">           <CopyToOutputDirectory>Always</CopyToOutputDirectory>           <TransformOnBuild>true</TransformOnBuild>       </Content>       <NoneInclude="Nlog.Release.config">           <IsTransformFile>true</IsTransformFile>           <DependentUpon>Nlog.config</DependentUpon>       </None>   </ItemGroup>

Content of nlog.Release.config

<?xml version="1.0" encoding="utf-8"?><!--For more information on using transformations see the web.config examples at http://go.microsoft.com/fwlink/?LinkId=214134.--><nlogxmlns="http://www.nlog-project.org/schemas/NLog.xsd"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://www.nlog-project.org/schemas/NLog.xsd NLog.xsd">    <targetsasync="true">        <targetxsi:type="WebService"name="Splunk"url="NEWURL"protocol="JsonPost"encoding="utf-8"preAuthenticate="true"xdt:Transform="SetAttributes(url)"xdt:Locator="Match(name)">        </target>    </targets></nlog>

If NEWURL is a variable

var token = Environment.GetEnvironmentVariable("YOURURL");     if (!string.IsNullOrWhiteSpace(token))     {       var currentFolder = Path.GetDirectoryName(Assembly.GetEntryAssembly().Location);       var nlogFolder = $"{currentFolder}/nlog.config";         var configText = File.ReadAllText(nlogFolder);       var updatedConfig = configText         .Replace("NEWURL", token);         File.WriteAllText(nlogFolder, updatedConfig);     }var logger = NLogBuilder.ConfigureNLog("nlog.config").GetCurrentClassLogger();//...