add example

Author: ghogen

docs/containers/docker-compose-properties.md

@@ -41,6 +41,46 @@ The following table shows the MSBuild properties available for Docker Compose pr
 |DockerServiceUrl| dcproj | The URL to use when launching the browser.  Valid replacement tokens are "{ServiceIPAddress}", "{ServicePort}", and "{Scheme}".  For example: {Scheme}://{ServiceIPAddress}:{ServicePort}|-|
 |DockerTargetOS| dcproj | The target OS used when building the Docker image.|-|
 
+## Example
+
+If you change the location of the docker compose files, by setting `DockerComposeBaseFilePath` to a relative path, then you also need to make sure that the build context is changed so that it references the solution folder. For example, if your docker compose file is a folder called *DockerComposeFiles*, then docker compose file should set the build context to ".." or "../..", depending on where it is relative to the solution folder.
+
+```xml
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="15.0" Sdk="Microsoft.Docker.Sdk">
+  <PropertyGroup Label="Globals">
+    <ProjectVersion>2.1</ProjectVersion>
+    <DockerTargetOS>Windows</DockerTargetOS>
+    <ProjectGuid>154022c1-8014-4e9d-bd78-6ff46670ffa4</ProjectGuid>
+    <DockerLaunchAction>LaunchBrowser</DockerLaunchAction>
+    <DockerServiceUrl>{Scheme}://{ServiceIPAddress}{ServicePort}</DockerServiceUrl>
+    <DockerServiceName>webapplication1</DockerServiceName>
+    <DockerComposeBaseFilePath>DockerComposeFiles\mydockercompose</DockerComposeBaseFilePath>
+    <AdditionalComposeFilePaths>AdditionalComposeFiles\myadditionalcompose.yml</AdditionalComposeFilePaths>
+  </PropertyGroup>
+  <ItemGroup>
+    <None Include="DockerComposeFiles\mydockercompose.override.yml">
+      <DependentUpon>DockerComposeFiles\mydockercompose.yml</DependentUpon>
+    </None>
+    <None Include="DockerComposeFiles\mydockercompose.yml" />
+    <None Include=".dockerignore" />
+  </ItemGroup>
+</Project>
+```
+
+The *mydockercompose.yml* file should look like this, with the build context set to the relative path of the solution folder (in this case, `..`).
+
+```yml
+version: '3.4'
+
+services:
+  webapplication1:
+    image: ${DOCKER_REGISTRY-}webapplication1
+    build:
+      context: ..
+      dockerfile: WebApplication1\Dockerfile
+```
+
 > [!NOTE]
 > DockerComposeBuildArguments, DockerComposeDownArguments, and DockerComposeUpArguments are new in Visual Studio 2019 version 16.3.