src/libraries/System.Runtime.Caching/src/PACKAGE.md
Packaged set of simple caching API's derived from those of the same namespace available in .NET Framework since 4.0. This package is intended for use as a bridge when porting .NET Framework applications to .NET.
Microsoft.Extensions.Caching.Memory/IMemoryCache is recommended over System.Runtime.Caching/MemoryCache because it's better integrated into ASP.NET Core. For example, IMemoryCache works natively with ASP.NET Core dependency injection.
Use System.Runtime.Caching/MemoryCache as a compatibility bridge when porting code from .NET 4.x to .NET Core.
The main types provided by this library are:
System.Runtime.Caching.MemoryCacheMemoryCache.PhysicalMemoryLimit property is only supported on windows.
System.Runtime.Caching is released as open source under the MIT license. Bug reports and contributions are welcome at the GitHub repository.