In Visual Studio 2015, developers are provided with a suite of tools and options for building a wide array of applications and libraries. Among these tools are Shared Projects and Class Libraries, each serving distinct purposes and offering unique capabilities. Below, we explore what differentiates these two project types and where each might be most beneficial in the development cycle.

Overview

Shared Project

A Shared Project in Visual Studio is essentially a container for code that can be used across multiple projects. Shared Projects themselves do not output any built artifacts or assemblies. Instead, they are used for code sharing and reuse across different platforms or project types. The code within a Shared Project is included in the build process of the consuming projects, compiling directly into those projects' outputs. Shared Projects are ideal for sharing code within the same solution, across projects that target different platforms, such as .NET, Android, and iOS.

Class Library

A Class Library, on the other hand, is a project type that compiles into an assembly (DLL). This DLL can then be referenced by other projects, regardless of the programming language used, as long as it's compatible with the .NET environment. Class Libraries are best suited for components or classes that provide specific functionality you want to encapsulate and hide from other projects, or when you want a reusable library that can be distributed independently.

Technical Differences

1. Build Output
   • Shared Project: No direct build output; included directly in referencing projects.
   • Class Library: Compiles into an assembly (DLL).
2. Code Sharing and Reuse
   • Shared Project: Code shared at the source level. Changes reflect immediately across all projects referencing it.
   • Class Library: Code is reused through the compiled assembly. Requires recompilation and redistribution for changes.
3. Platform Compatibility
   • Shared Project: Efficient for multi-platform projects (using compiler directives for platform-specific code).
   • Class Library: Typically targets a specific version of the .NET framework or platform.
4. Project References
   • Shared Project: Referenced by the solution directly, not compilable independently.
   • Class Library: Referenced as a DLL, which increases encapsulation and may enhance deployment options.
5. Use Cases
   • Shared Project: Common business logic, inline code reuse across platforms or projects requiring tight integration.
   • Class Library: Encapsulated functionality, third-party libraries, plugins, or services meant for external consumption.

Example Usage

Shared Project Example

Imagine developing a cross-platform application using Xamarin where the business logic needs to be the same across Android, iOS, and Windows projects. Instead of duplicating the logic or dealing with shared assemblies, a Shared Project would allow you to include the same C# code in all these projects seamlessly.

• Debugging and Maintenance: With Shared Projects, debugging feels more seamless as you are always working with the raw source. On the contrary, Class Libraries may require additional steps to load debugging symbols (.pdb files) when source stepping.
• Versioning: Class Libraries can have version numbers and can be versioned independently. This is not inherent in Shared Projects.
• Simplicity vs. Encapsulation: While Shared Projects simplify code sharing and reduce redundancy, Class Libraries are advantageous for encapsulation and modularity.