Embedding DLLs in a compiled executable

I highly recommend to use Costura.Fody - by far the best and easiest way to embed resources in your assembly. It's available as NuGet package.

Install-Package Costura.Fody

After adding it to the project, it will automatically embed all references that are copied to the output directory into your main assembly. You might want to clean the embedded files by adding a target to your project:

Install-CleanReferencesTarget

You'll also be able to specify whether to include the pdb's, exclude certain assemblies, or extracting the assemblies on the fly. As far as I know, also unmanaged assemblies are supported.

Update

Currently, some people are trying to add support for DNX.

Update 2

For the lastest Fody version, you will need to have MSBuild 16 (so Visual Studio 2019). Fody version 4.2.1 will do MSBuild 15. (reference: Fody is only supported on MSBuild 16 and above. Current version: 15)

If they're actually managed assemblies, you can use ILMerge. For native DLLs, you'll have a bit more work to do.

See also: How can a C++ windows dll be merged into a C# application exe?

The excerpt by Jeffrey Richter is very good. In short, add the library's as embedded resources and add a callback before anything else. Here is a version of the code (found in the comments of his page) that I put at the start of Main method for a console app (just make sure that any calls that use the library's are in a different method to Main).

AppDomain.CurrentDomain.AssemblyResolve += (sender, bargs) =>
        {
            String dllName = new AssemblyName(bargs.Name).Name + ".dll";
            var assem = Assembly.GetExecutingAssembly();
            String resourceName = assem.GetManifestResourceNames().FirstOrDefault(rn => rn.EndsWith(dllName));
            if (resourceName == null) return null; // Not found, maybe another handler will find it
            using (var stream = assem.GetManifestResourceStream(resourceName))
            {
                Byte[] assemblyData = new Byte[stream.Length];
                stream.Read(assemblyData, 0, assemblyData.Length);
                return Assembly.Load(assemblyData);
            }
        };

.NET Core 3.0 natively supports compiling to a single .exe

The feature is enabled by the usage of the following property in your project file (.csproj):

    <PropertyGroup>
        <PublishSingleFile>true</PublishSingleFile>
    </PropertyGroup>

This is done without any external tool.

See my answer for this question for further details.

You could add the DLLs as embedded resources, and then have your program unpack them into the application directory on startup (after checking to see if they're there already).

Setup files are so easy to make, though, that I don't think this would be worth it.

EDIT: This technique would be easy with .NET assemblies. With non-.NET DLLs it would be a lot more work (you'd have to figure out where to unpack the files and register them and so on).

Another product that can handle this elegantly is SmartAssembly, at SmartAssembly.com. This product will, in addition to merging all dependencies into a single DLL, (optionally) obfuscate your code, remove extra meta-data to reduce the resulting file size, and can also actually optimize the IL to increase runtime performance.

There is also some kind of global exception handling/reporting feature it adds to your software (if desired) that could be useful. I believe it also has a command-line API so you can make it part of your build process.

The following method DO NOT use external tools and AUTOMATICALLY include all needed DLL (no manual action required, everything done at compilation)

I read a lot of answer here saying to use ILMerge, ILRepack or Jeffrey Ritcher method but none of that worked with WPF applications nor was easy to use.

When you have a lot of DLL it can be hard to manually include the one you need in your exe. The best method i found was explained by Wegged here on StackOverflow

Copy pasted his answer here for clarity (all credit to Wegged)

1) Add this to your .csproj file:

<Target Name="AfterResolveReferences">
  <ItemGroup>
    <EmbeddedResource Include="@(ReferenceCopyLocalPaths)" Condition="'%(ReferenceCopyLocalPaths.Extension)' == '.dll'">
      <LogicalName>%(ReferenceCopyLocalPaths.DestinationSubDirectory)%(ReferenceCopyLocalPaths.Filename)%(ReferenceCopyLocalPaths.Extension)</LogicalName>
    </EmbeddedResource>
  </ItemGroup>
</Target>

2) Make your Main Program.cs look like this:

[STAThreadAttribute]
public static void Main()
{
    AppDomain.CurrentDomain.AssemblyResolve += OnResolveAssembly;
    App.Main();
}

3) Add the OnResolveAssembly method:

private static Assembly OnResolveAssembly(object sender, ResolveEventArgs args)
{
    Assembly executingAssembly = Assembly.GetExecutingAssembly();
    AssemblyName assemblyName = new AssemblyName(args.Name);

    var path = assemblyName.Name + ".dll";
    if (assemblyName.CultureInfo.Equals(CultureInfo.InvariantCulture) == false) path = String.Format(@"{0}\{1}", assemblyName.CultureInfo, path);

    using (Stream stream = executingAssembly.GetManifestResourceStream(path))
    {
        if (stream == null) return null;

        var assemblyRawBytes = new byte[stream.Length];
        stream.Read(assemblyRawBytes, 0, assemblyRawBytes.Length);
        return Assembly.Load(assemblyRawBytes);
    }
}

If you are using .NET Core 3.0

You can do this with the dotnet publish command with PublishSingleFile property:

dotnet publish -r win-x64 -c Release /p:PublishSingleFile=true

The only downside is you end up with a single EXE file with a huge size.

It's possible but not all that easy, to create a hybrid native/managed assembly in C#. Were you using C++ instead it'd be a lot easier, as the Visual C++ compiler can create hybrid assemblies as easily as anything else.

Unless you have a strict requirement to produce a hybrid assembly, I'd agree with MusiGenesis that this isn't really worth the trouble to do with C#. If you need to do it, perhaps look at moving to C++/CLI instead.