ILMerge is a utility that can be used to merge multiple .NET assemblies into a single assembly. It is freely available for use from the Tools & Utilities page at the Microsoft .NET Framework Developer Center.

Commercial use permitted:
The language of ILMerge's license has raised many questions. In a nutshell: commercial use is permitted, redistribution is not. Read the license carefully for full details since I am not (nor do I wish to be!) a lawyer.

If you have any problems using it, please get in touch. (mbarnett _at_ microsoft _dot_ com)

ILMerge takes a set of input assemblies and merges them into one target assembly. The first assembly in the list of input assemblies is the primary assembly. When the primary assembly is an executable, then the target assembly is created as an executable with the same entry point as the primary assembly. Also, if the primary assembly has a strong name, and a .snk file is provided, then the target assembly is re-signed with the specified key so that it also has a strong name.

ILMerge is packaged as a console application. But all of its functionality is also available programmatically.

There are several options that control the behavior of ILMerge. See the documentation that comes with the tool for details.

The current version is 2.8.0626 (created on 26 June 2008). NOTE: There is no longer a version of ILMerge that runs in the v1.1 runtime.

The v2.0 version of ILMerge runs in the v2.0 .NET Runtime, but it is also able to merge v1 or v1.1 assemblies. However, it can merge PDB files only for v2 assemblies.

The v2 version of ILMerge was built with v2.0.50727 of the .NET Runtime. If you have an earlier version (e.g., Beta2 is v2.0.50215), then you need to use a config file: ILMerge.exe.config. (Use "Save As..." to save the file. If you copy it from the browser, I believe you will get some extraneous characters that the browser throws in.)

Currently, ILMerge works only on Windows-based platforms. It does not yet support Rotor or Mono.

If you use ASP.NET v2.0, then it provides a tool (based on ILMerge) to combine assemblies created during precompilation. You can get more details from the ASP.NET web site.

GUI Wrappers

There are several GUIs available that wrap ILMerge:

• Tomer Shalev and Lior Brill have written Gilma.
• DILMerge has been written by Mauro Venturini that specifically targets and integrates with Borland Delphi for .NET.
• Anthony Nystrom has one named NuGenUnify.

Redistribution

From time to time I have gotten requests from ILMerge users who would like to redistribute ILMerge as part of their own application because their users need it on the client machines in order to run the application. Unfortunately, the license for ILMerge does not permit redistribution. However, I have just found out about an alternative solution that may work for you. The Visual Studio Power Toys team has just put out a new product, the Power Toys Pack Installer. It brings up a single window in which one can select multiple tools. It then aggregates the license agreements so that one click by the user accepts all of the licenses (of the selected tools). It then runs the installer for each tool in turn. So it isn’t redistributing the tools, but consolidating their license agreement screens and installers so that users do not have to manually go to the web site for each tool and install it themselves. The source code the Pack Installer is under a very liberal license, the Microsoft Permissive License (Ms-PL). This means that you can use their source code for your own application’s installer to achieve the same effect. I do not know anything about the code, so if you have questions about it, please contact them directly.

Change History