Support Statement: Consolidating Shared Code Files

Q: My VB6 system has a lot of code files that are shared by different VBPs,  How can I consolidate these into assemblies and reference them from their?

A. User the ShareFile Migration process.

Overview

The default translation process for a VBP creates a .NET version of each code file referenced by the VBP. If multiple VBPs reference the same code file, there will be multiple copies of the shared file translations: one for each VBP.  Restructuring the generated code files to remove this duplication is a common upgrade feature that we call Shared Files Consolidation.   Many different configurations of code files are feasible.  The constraints arise from the external dependencies that are contained within each file that must still be satisfied after consolidation without creating build cycles or other naming conflicts.     

For a large-scale VB6 application with shared files, it is possible to reproduce something close to the structure of the legacy app using .NET linked files, but linked files are still not a straight conversion: we would have to make some decisions and also deal with assigning and using namespaces.   Code file linking has other disadvantages for builds and deployments so it has a higher cost of ownership.  Consequently, there is some value in hosting each shared file in only one assembly and referencing it there.   gmStudio can help implement this re-hosting process. 

Assuming we want to go with hostingrather than linking, we begin with a guiding principle: each file should be referenced by at most one assembly (the host).  Once in that host, the file will become a class in the namespace of the host.   If a class is used by other assemblies, those others must reference the host assembly and use the shared class members through the host namespace.  But, as always, the problems are in the details. 

Regarding shared files, we offer these options:

Make an independent copy of the shared file for each referencing project. This is the default, and it is typically used only for the initial iterations of upgrade solution development.

1. Compile the shared file into one of the translated projects and reference the shared file content through that host project.  This is done using the "SharedFile" statement described in this article.

2. Put a single copy of the shared file in a specified location in the source directory and reference the shared file content through a link to the shared file. This can be achieved fairly easily with a few PostEdit commands in the translation script; however additional work is also needed to set a namespace for the linked file and then use that namespace in references to the contents of the file.

How To: Shared Files Consolidation

Shared Files Consolidation is a three step process:

1) Translate VBPs to produce desired VBI files
2) Prepare a ShareFile script and process it using the SharedFile utility: gmSharedFile \ABCTeam\csh\SharedFile.xml (see discussion of how to integrate this with your project below).
3) Use ShareFiles commands in a second set of translation scripts to produces consolidated translations

Example:

In this example, the shared files are into ABCCommon.VBP.  Note: ABCCommon.VBP does not need to actually exist on the legacy side. It may be a VBP developed by hand, adding references to COM and Code files as needed.

SharedFile.xml
Used in Step 2: gmSharedFile \ABCTeam\csh\SharedFile.xml

Notice that two outputs are specified:

• SharedFile.out is a log file for informational purposes

• Registry_SharedFile.xml is a file that will contain the SharedFile commands to direct shared file consolidation in Step 3.

SharedFile.out 

This is a log file generated by Step 2.  It is information only.  The location of this file is set by the SharedFile@ReportFile attribute.

Registry_SharedFile.xml

This is a rules file generated by Step 2.  It contains various commands to direct the shared files consolidation.  The location of this file is set by the SharedFile@RegistryFile attribute.

Activating SharedFiles migration

The Registry-SharedFile commands generated by the SharedFiles utility should be added to a GlobalSettings script. Processing that GlobalSettings script stores the command in a GlobalSettings VBI file.  

Loading the GlobalSettings.VBI file during translation of your VBPs will result in translations that reference shared files in the desired host project(s) rather than locally.

In addition you must Select SharedFile=on, to tell gmBasic to apply SharedFile rules to the translations:

The FMStocks sample demonstrates the ShareFiles migration.

Integrating a gmSharedFile task into your project

If you wish to run gmSharedFile.exe from within gmStudio, you must add a Shared File script to the project that references the SharedFile analysis script and a SharedFile.exe. For example:

Where GMExecShared is specified in the project settings dialog:

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Now when we run the task in gmStudio, gmSharedFile will process the SharedFile script instead of gmBasic:

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