Siren

Summary

It is a simple command line tool that can be installed from NuGet. When run, it will take a C# database migration context assembly, and create an entity relationship (ER) diagram in Mermaid syntax.

Usage

Installation

You can install the siren-gen tool via the following .NET command

dotnet tool install -g Gman.Siren

Running the tool

Run the command as follows:

siren-gen -a [--assemblyPath] <PATH_TO_MIGRATION_ASSEMBLY> -c [--connectionString] <DATABASE_CONNECTION_STRING> -o [--outputPath] <PATH_TO_OUTPUT_MARKDOWN_FILE> -m [--markdownAnchor] <MARKDOWN_ANCHOR>

• PATH_TO_MIGRATION_ASSEMBLY (optional, required if connection string not provided) - this will be the location of the built .NET DLL containing the database migration you wish to map to an ER diagram.
• DATABASE_CONNECTION_STRING (optional, required if assembly not provided) - this can be set to the connection string of a (currently online), accessible database. Siren uses the SchemaSearch library to run compatible system information schema queries using Entity Framework; this is another potential rendering option in the absence of a migration assembly.
• PATH_TO_OUTPUT_MARKDOWN_FILE (required) - this points to a file (on your local file system) where the markdown should be generated; includes the full file name. The file does not have to be a markdown (.md) file.
• MARKDOWN_ANCHOR (optional) - this is useful for updating README.md files that may be associated with your domain model (i.e. committed in a git repository). If the markdown anchor is specified, and the output file contains that markdown anchor (for example "### My Domain Model Diagram"), then the Siren tool will only add or replace any existing diagram it finds under that anchor, and leave the rest of the document unmodified.

Example Github action

• An example workflow file that will update the README.md of a (non-master) branch whenever a change is detected in the Migrations folder - Not.Again
• The resulting domain model section in the README.md