Create a Single .NET Executable with Multiple Assemblies

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If you want to create a single .NET executable there are several possibilities. In the past I’ve used Jeffrey Richter’s technique of embedding DLLs as resources and loading these into memory from the Manifest Resource Stream on startup. While this works well, it does require a bit of extra code to not try to access anything in an assembly until after it’s been loaded at startup.

In the interest of cleaner code, I decided to give ILMerge a go.

It’s simple to install ILMerge into your application using NuGet:

PM> Install-Package ilmerge -Version 2.14.1208

To run ILMerge on your release builds, add an AfterBuild section to your default projects .csproj file:

  <Target Name="AfterBuild" Condition=" '(Configuration)' == 'Release' ">     <CreateItem Include="@(ReferenceCopyLocalPaths)" Condition="'%(Extension)'=='.dll'">       <Output ItemName="AssembliesToMerge" TaskParameter="Include" />     </CreateItem>     <PropertyGroup>       <ReferenceAssemblies>C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5.2</ReferenceAssemblies>     </PropertyGroup>     <Message Importance="high" Text="Executing ILMerge...with target platform from(ReferenceAssemblies)" />
    <Exec Command="&quot;(SolutionDir)\packages\ILMerge.2.14.1208\tools\ILMerge.exe" /target:exe /out:@(MainAssembly) /internalize /targetplatform:v4,"(ReferenceAssemblies)&quot; &quot;@(IntermediateAssembly)&quot; @(AssembliesToMerge->'&quot;%(FullPath)&quot;', ' ')" />
    <Delete Files="@(ReferenceCopyLocalPaths->'$(OutDir)%(DestinationSubDirectory)%(Filename)%(Extension)')" />
  </Target>

Note: If you receive this error from ILMerge when building your release executable:

An exception occurred during merging:
ILMerge.Merge: There were errors reported in AWSSDK.Core’s metadata.
Array dimensions exceeded supported range.
at ILMerging.ILMerge.Merge()
at ILMerging.ILMerge.Main(String[] args)

It’s because ILMerge doesn’t currently support the new portable PDB format.
https://github.com/Microsoft/ILMerge/issues/29
https://github.com/Microsoft/ILMerge/issues/11

If you can live without the .pdb files being merged into a single PDB file add /ndebug to the Exec command.

This is a temporary workaround for issues with ILMerge where it cannot process the new portable .NET PDB format.

An excellent resource on PDB files is John Robbins’s : PDB Files: What Every Developer Must Know :

A .NET PDB only contains two pieces of information, the source file names and their lines and the local variable names. All the other information is already in the .NET metadata so there is no need to duplicate the same information in a PDB file.