AssemblyAttributeSearch

This is a small small .Net Standard library/helper to provide greatly simplified convenience methods for dynamically finding, filtering, and initializing classes based on Custom Attributes. It provides a simpel convenience methods to allow searching for all instances of a Custom Attribute type.

In addition, you may specify an optional Class/Interface filter to only return types that implement the given class/interface.

The results will have the details of the Attribute found, as well as the class type for the calling code to use (e.g. process, instantiate dynamically, etc.).1

The default behavior assumes that there may be instances where Interfaces, and classes are defined in separate class Librareis and may in which the Assembly may not yet be loaded. In which case the local assemblies -- in the same root/bin folder as the specified assembly -- are eagerly loaded (e.g. force loaded) so that all libraries are available to be searched.

This was important for my use case whereby I wanted to have a generic Factory that could create instances of any class that implmented my interface and had appropriate metadata defined by my Custom Attribute. This allowed develoeprs to create many implementations easily without any impact to the core framework that could instantiate and implement the use of those classes.

NOTE: In the context of Azure Functions, the Assembly.GetExecutingAssembly() method results in a dynamic func and not the original project assembly, therefore the local class libraries could not be found and loaded as expected. The solution is to simply use the Assembly property of a specific type (e.g. this.GetType().Assembly) that exists in the main project assembly and everythign will resolve as expected; as noted in the samples below.

Nuget Package

To use behaviors in your project, add the AssemblyAttributeSearch NuGet package to your project.

Project Goals & Benefits (Why did I share this?)

• Provide a very simple and lightweight library for searching/filtering all assemblies for Classes and their associated Attributes.
• Implement internal static caching for performance so that reflection calls do not need to be made for the same searches more than once.
• Return all related data for both the Attribute & Class Types in the response so that no additional Reflection processing is needed. ** I originally used FluentAssemblyScanner (a great looking project) however did not want to have to scan assemblies and then do additional lookups to get my Attribute data again. ** In addition, much of the FluentAssemblyScanner library was unused so something even lighter weight could meet my needs (and many others I believe).

Usage

To get all classes & attribute info. for all classes denoted with a given JediAttribute Custom Attribute:

var thisAssembly = this.GetType().Assembly;

//This gets the list of all search results...
var allJediClassInfoList = AssemblyAttributeSearch<JediAttribute>.FindAllAttributedClasses(thisAssembly);

//This convenience method lets us instanticate an instance (via Relfection)
var dynamicallyCreatedJedi = allJediClassInfoList.FirstOrDefault()?.CreateInstanc<IJedi>();

To get only the classes & attribute info. with a given JediAttribute and that also implements the IJediMaster Interface:

var thisAssembly = this.GetType().Assembly;

//This gets the list of all search results...
var jediMasterClassInfoList = AssemblyAttributeSearch<JediAttribute>.FindAllAttributedClasses(thisAssembly, typeof(IJediMaster));

//This convenience method lets us instanticate an instance (via Relfection)
var dynamicallyCreatedJediMaster = jediMasterClassInfoList.FirstOrDefault()?.CreateInstanc<IJediMaster>();

Or if you just want to force load the local class libraries via the Helper and then process with your own Reflection Logic:

//Eagerly load all local assemblies...
AssemblyLoadHelper.ForceLoadClassLibraries(this.GetType().Assembly);

//Now you can retrieve and process all types in all assemblies even if they have not yet been lazy initialized by .Net Framework...
var allTypesInAllLocalAssemblies = AppDomain.CurrentDomain.GetAssemblies().SelectMany(a => a.GetTypes());

/*
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Copyright (c) 2018

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