How Can LINQ Efficiently Find All Derived Types of a Specified Base Type?

Finding Derived Types of a Specified Type

In programming, it is often necessary to determine all derived types of a given base type. Traditionally, this has been achieved through laborious techniques such as iterating over all types in loaded assemblies and manually checking for assignability to the target type.

However, a more efficient and elegant solution exists using LINQ (Language Integrated Query). The following code snippet provides a straightforward and performant way to accomplish this task:

var listOfDerivedTypes = (
                from domainAssembly in AppDomain.CurrentDomain.GetAssemblies()
                from type in domainAssembly.GetTypes()
                where typeof(BaseTypeName).IsAssignableFrom(type)
                select type).ToArray();

Alternative Fluent Syntax:

The LINQ expression can also be written in a more fluent style for enhanced readability:

var listOfDerivedTypes = AppDomain.CurrentDomain.GetAssemblies()
                .SelectMany(domainAssembly => domainAssembly.GetTypes())
                .Where(type => typeof(BaseTypeName).IsAssignableFrom(type))
                .ToArray();

Customizations:

• Only Publicly Visible Types: To retrieve only types that are publicly visible, use domainAssembly.GetExportedTypes() instead of domainAssembly.GetTypes().
• Exclude Original Base Class: To prevent the original base type from being included in the results, add && type != typeof(BaseTypeName) to the where clause.
• Exclude Abstract Classes: To exclude abstract classes, add && ! type.IsAbstract to the where clause.
• Generic Types: Handling generic types requires additional considerations. For guidance, refer to the linked resources in the "Details" section.

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