ILMerge and SDL Tridion Development

SDL Tridion comes with a nice feature that allows developers to upload DLLs as managed Assemblies (Template Building Blocks, Workflow Activities) or to reference DLLs in the file system (Event System, Resolvers). While implementing SDL Tridion we normally have to re-use projects or external assemblies across different areas in our implementation which is normal in modular software development.

The fact of re-usability is mandatory and key in any software implementation. .NET code is executed in boundaries called Application Domains, at execution time the .NET Framework creates an Application Domain which will contain the executing assembly and any other dependency (Assemblies and Resources). The .NET Framework looks for dependencies in the following places.

1.     Checks for assemblies referenced in Configuration Files (<runtime> element)

2.     Checks for assemblies in the same Folder

3.     Check for assemblies in the Global Assembly Cache

However the way SDL Tridion executes code brings some issues. .NET TBBs and Workflow Activities are dynamically loaded from records in the Content Manager database. It means we cannot reference assemblies in the same folders or dependencies in configuration files (because there is no folder or configuration file involved), it leaves GAC as the only option

So, the question is, What are my alternatives when I want to use a shared library or project between different areas in our implementation?, for instance I have developed a Logging Framework or XML Parsing libraries that are used by Event System and TBBs as well as Workflow Activities. In that scenario the only option is to register those shared libraries in the GAC (Global Assembly Cache) which makes deployment process more difficult and managing dependencies even more complicated.

ILMerge allows to merge different assemblies (libraries, projects) into a single assembly which in fact will make all the code and functionality available in different libraries and projects in the same Application Domain. With ILMerge we can have a logging library or project references in Workflow Activities as well as referenced in TBBs. ILMerge will generate a single assembly that contains the result of merging different assemblies (executing assemblies and dependencies) in the same DLL so we don’t need to worry about registering all the shared dependencies in the GAC.

DD4T and SDL Reference Implementation are using that approach in order to make compilation and deployment easier.

ILMerge can be downloaded from http://www.microsoft.com/en-us/download/details.aspx?id=17630

Here a sample on how DD4T templates are compiled using ILMerge. This sample shows the Post Build Event configured in the DD4T Template Project

Command Segment	Description
"C:\Development\dynamic-delivery-4-tridion-master\dotnet\Dynamic Delivery Publishing Solution Items\ilmerge"	ILMerge location
/lib:"C:\Windows\Microsoft.NET\Framework\v4.0.30319" /lib:"C:\Program Files (x86)\Tridion\bin\client"	Use a /lib parameter in order to specify paths where ILMerge will look for dependencies that should be merged in the resulting assembly
/t:dll	Target Format (DLL, EXE)
/targetplatform:v4,C:\Windows\Microsoft.NET\Framework\v4.0.30319	Specifies that the DLL is intended for the .NET Framework 4 and higher
/out:"C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.Templates.merged.dll"	Resulting merged DLL path
"C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.ContentModel.Contracts.dll" "C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.ContentModel.dll" "C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.Templates.Base.dll" "C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.ContentModel.XmlSerializers.dll" "C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.Templates.dll"	The list of assemblies that should be merged

"C:\Development\dynamic-delivery-4-tridion-master\dotnet\Dynamic Delivery Publishing Solution Items\ilmerge"

/lib:"C:\Windows\Microsoft.NET\Framework\v4.0.30319"

/lib:"C:\Program Files (x86)\Tridion\bin\client"

/t:dll

/targetplatform:v4,C:\Windows\Microsoft.NET\Framework\v4.0.30319

/out:"C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.Templates.merged.dll"

"C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.ContentModel.Contracts.dll" "C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.ContentModel.dll" "C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.Templates.Base.dll" "C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.ContentModel.XmlSerializers.dll" "C:\Development\dynamic-delivery-4-tridion-master\build\DD4T.Templates.dll"