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.NET Framework Class Library in Visual Studio

The .NET Framework class library is made up of namespaces. Each namespace contains types that you can use in your program: classes, structures, enumerations, delegates, and interfaces.

When you create a Visual Basic or Visual C# project in Visual Studio, the most common base class DLLs (assemblies) are already referenced. However, if you have to use a type that is in a DLL not already referenced, you will have to add a reference to the DLL. For more information, see Adding and Removing References.

The topics in the following section provide the following information:

  • Lists of the most important namespaces for each feature area.

  • Links to reference topics in the .NET Framework about each major namespace.

  • Links to procedural and conceptual topics about how to use those namespaces in your Visual Basic and Visual C# applications.

In This Section

  • Inside the .NET Framework
    Provides links to important information about the common language runtime, assemblies, common type system, metadata, interoperability, security, and other features of the .NET Framework.

  • .NET Framework Class Library
    Describes the functionality provided by the types (classes, structures, enumerations, delegates, and interfaces) in the .NET Framework and lists the base data types provided by the System namespace.

  • Microsoft .NET Web site (
    Provides the latest information and resources about .NET.

  • Adding and Removing References
    Explains how to reference external projects and .NET and COM components so that you can use them in your application.

  • Assemblies
    Provides links to topics that explain what assemblies do and how to use them.

See Also

Other Resources

.NET Framework Core Development

.NET Framework Advanced Development