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What is NuGet, and what problem does it solve for .NET developers? What is the Global Assembly Cache (GAC), and is it still relevant in modern .NET? How does NuGet resolve version conflicts when two packages depend on different versions of the same transitive dependency? What is strong naming of assemblies, and why is it much less commonly required in modern .NET? How do you create and publish your own NuGet package from a class library project? What is the difference between a NuGet package's dependency group targeting different frameworks, and why do multi-targeted packages need this? What is a NuGet lock file (packages.lock.json), and what problem does it solve for reproducible builds? What are NuGet package sources, and how do you configure a project to pull packages from a private/internal feed alongside NuGet.org? What is Central Package Management (CPM) in NuGet, and how does Directory.Packages.props centralize version control? How does semantic versioning apply to NuGet packages, and what do version range operators like [1.0,2.0) mean?
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What is an assembly in .NET, and what does it contain?

Beginner

Answer

An assembly is the fundamental unit of deployment and versioning in .NET -- a compiled .dll or .exe file containing IL (Intermediate Language) code, type metadata, and a manifest describing the assembly's identity (name, version, culture) and its references to other assemblies. The CLR loads assemblies at runtime to execute the types and members they define.
// Building a project produces an assembly:
dotnet build
// Output: bin/Debug/net8.0/MyApp.dll -- this is the assembly
Real-world example A shared business-logic library is compiled into MyCompany.Core.dll, an assembly referenced by multiple separate application assemblies (web API, background worker, console tool) without duplicating the source code.

Common follow-ups: What's the difference between a private and shared assembly?;How does the CLR locate assemblies at runtime?

.NET CLI SDK & Project Structure (csproj);CLR & Runtime
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