How to Integrate ILMerge into Visual Studio Build Process to Merge Assemblies?

The "MSBuild ILMerge task" (or MSBuild.ILMerge.Task) NuGet package makes this process quite simple. It defaults to merging any "copy local" references into your main assembly.

Note: Although the packages have similar names, this one is different from ILMerge.MSBuild.Tasks that Davide Icardi mentioned in his answer. The one I'm suggesting here was first published in August 2014.

Here an alternative solution:

1) Install ILMerge.MSBuild.Tasks package from nuget

PM> Install-Package ILMerge.MSBuild.Tasks

2) Edit the *.csproj file of the project that you want to merge by adding the code below:

  <!-- Code to merge the assemblies into one:setup.exe -->
  <UsingTask TaskName="ILMerge.MSBuild.Tasks.ILMerge" AssemblyFile="$(SolutionDir)\packages\ILMerge.MSBuild.Tasks.1.0.0.3\tools\ILMerge.MSBuild.Tasks.dll" />
  <Target Name="AfterBuild">
    <ItemGroup>
      <MergeAsm Include="$(OutputPath)$(TargetFileName)" />
      <MergeAsm Include="$(OutputPath)LIB1_To_MERGE.dll" />
      <MergeAsm Include="$(OutputPath)LIB2_To_MERGE.dll" />
    </ItemGroup>
    <PropertyGroup>
      <MergedAssembly>$(ProjectDir)$(OutDir)MERGED_ASSEMBLY_NAME.exe</MergedAssembly>
    </PropertyGroup>
    <Message Text="ILMerge @(MergeAsm) -&gt; $(MergedAssembly)" Importance="high" />
    <ILMerge InputAssemblies="@(MergeAsm)" OutputFile="$(MergedAssembly)" TargetKind="SameAsPrimaryAssembly" />
  </Target>

3) Build your project as usual.

Some more information that might be useful to some people implementing Scott Hanselman's solution.

When I first set this up it would complain about not being able to resolve references to System.Core, etc. It is something to do with .NET 4 support. Including a /lib argument pointing to the .NET 4 Framework directory fixes it (in fact just include the $(MSBuildBinPath)).

/lib:$(MSBuildBinPath)

I then found that IlMerge would hang while merging. It was using a bit of CPU and a lot of RAM but wasn't outputting anything. I found the fix on stackoverflow of course.

/targetplatform:v4

I also found that some of the MSBuild properties used in Scott's blog article relied on executing MsBuild from the project's directory, so I tweaked them a bit.

I then moved the targets & ilmerge.exe to the tools folder of our source tree which required another small tweak to the paths...

I finally ended up with the following Exec element to replace the one in Scott's original article:

<Exec Command="&quot;$(MSBuildThisFileDirectory)Ilmerge.exe&quot; /lib:$(MSBuildBinPath) /targetplatform:v4 /out:@(MainAssembly) &quot;$(MSBuildProjectDirectory)\@(IntermediateAssembly)&quot; @(IlmergeAssemblies->'&quot;%(FullPath)&quot;', ' ')" /> 

UPDATE I also found Logic Labs answer about keeping the CopyLocal behaviour and just excluding ilMerged assemblies from CopyLocal essential if you are using Nuget packages. Otherwise you need to specify a /lib argument for each package directory of referenced assemblies that aren't being merged.

The article Mixing Languages in a Single Assembly in Visual Studio seamlessly with ILMerge and MSBuild at http://www.hanselman.com/blog/MixingLanguagesInASingleAssemblyInVisualStudioSeamlesslyWithILMergeAndMSBuild.aspx demonstrates how to use ILMerge and MSBuild within a Visual Studio Project.

One issue I found with the article at: http://www.hanselman.com/blog/MixingLanguagesInASingleAssemblyInVisualStudioSeamlesslyWithILMergeAndMSBuild.aspx.

If you have any references that you do not wish to ILMerge then the code in the article fails because it overrides the default CopyLocal behaviour to do nothing.

To fix this - Instead of:

<Target Name="_CopyFilesMarkedCopyLocal"/> 

Add this entry to the targets file instead (.NET 3.5 only) (to filter out the non-ilmerge copylocal files, and treat them as normal)

<Target Name="AfterResolveReferences">
    <Message Text="Filtering out ilmerge assemblies from ReferenceCopyLocalPaths" Importance="High" />
    <ItemGroup>
        <ReferenceCopyLocalPaths Remove="@(ReferenceCopyLocalPaths)" Condition="'%(ReferenceCopyLocalPaths.IlMerge)'=='true'" />
    </ItemGroup>
</Target>