The common language runtime allows you to add keyword-like descriptive declarations, called attributes, to annotate programming elements such as types, fields, methods, and properties. When you compile your code for the runtime, it is converted into common intermediate language (CIL) and placed inside a portable executable (PE) file along with metadata generated by the compiler. Attributes allow you to place extra descriptive information into metadata that can be extracted using runtime reflection services. The compiler creates attributes when you declare instances of special classes that derive from System.Attribute.
.NET uses attributes for a variety of reasons and to address a number of issues. Attributes describe how to serialize data, specify characteristics that are used to enforce security, and limit optimizations by the just-in-time (JIT) compiler so the code remains easy to debug. Attributes can also record the name of a file or the author of code, or control the visibility of controls and members during forms development.
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Learn to retrieve information stored in attributes, including for an attribute instance, multiple instances for the same scope, multiple instances for different scopes, and attributes applied to class members.
Use attributes to associate metadata or declarative information in C#. Query attributes at run time with reflection APIs that describe assemblies, modules, and types.
Learn how attributes work in C#. You define custom attributes to add metadata to your code. You read those attributes to learn about the code at runtime
