title: Meaning of numbers in left column of output pane in Visual Studio when building
body: <p>I've wondered for years as to what is the meaning of numbers in the left column of the output pane in Visual Studio when doing a build.  The generally increase as each project in the solution gets built, but they also jump around as well.  For example:</p>
  
  <pre><code>1&gt;------ Rebuild All started: Project: MyCompany.MyProject1, Configuration: Debug Any CPU ------
  2&gt;------ Rebuild All started: Project: MyCompany.MyProject2, Configuration: Debug Any CPU ------
  3&gt;------ Rebuild All started: Project: MyCompany.MyProject3, Configuration: Debug Any CPU ------
  4&gt;------ Rebuild All started: Project: MyCompany.MyProject4, Configuration: Debug Any CPU ------
  4&gt;C:\SourcePath\MyApplication\MyNamespace\Views\MyFeature\MyCompany.MyProject2.csproj(172,3): warning MSB4011: "C:\MyPath1.CSharp.targets" cannot be imported again. It was already imported at "C:\MyPath2\MyCompany.Build.CustomAfterMicrosoftCSharpTargets.props (41,5)". This is most likely a build authoring error. This subsequent import will be ignored. 
  4&gt;  Restoring NuGet packages...
  4&gt;  To prevent NuGet from downloading packages during build, open the Visual Studio Options dialog, click on the Package Manager node and uncheck 'Allow NuGet to download missing packages'.
  4&gt;  Feeds used:
  4&gt;    C:\Users\MyUser\AppData\Local\NuGet\Cache
  4&gt;    C:\Users\MyUser\.nuget\packages\
  4&gt;    https://api.nuget.org/v3/index.json
  4&gt;    http://nuget.MyCompany.com/nuget/api/v2/
  4&gt;    C:\Program Files (x86)\Microsoft SDKs\NuGetPackages\
  4&gt;  
  4&gt;  All packages listed in MyPath5\packages.config are already installed.
  4&gt;  MyCompany.MyProject4 -&gt; MyPath6\MyCompany.MyProject4.dll
  5&gt;------ Rebuild All started: Project: MyCompany.MyNamespace.This.Something, Configuration: Debug Any CPU ------
  5&gt;  MyCompany.MyNamespace.This.Something -&gt; C:\SourcePath\MyApplication\MyNamespace\ThisLayer\Something\bin\Debug\MyCompany.MyNamespace.This.Something.dll
  3&gt;C:\SourcePath\MyApplication\MyNamespace\Views\MyFeature\MyCompany.MyProject2.csproj(172,3): warning MSB4011: "C:\MyPath1.CSharp.targets" cannot be imported again. It was already imported at "C:\MyPath2\MyCompany.Build.CustomAfterMicrosoftCSharpTargets.props (41,5)". This is most likely a build authoring error. This subsequent import will be ignored. 
  3&gt;  Restoring NuGet packages...
  </code></pre>