System.AppContext by: Microsoft

Provides the System.AppContext class, which allows access to the BaseDirectory property and other application specific data. Commonly Used Types: System.AppContext

System.Collections by: Microsoft

Provides classes that define generic collections, which allow developers to create strongly typed collections that provide better type safety and performance than non-generic strongly typed collections. Commonly Used Types: System.Collections.Generic.List<T> System.Collections.Generic.Dictionary<TKey, TValue> System.Collections.Generic.Queue<T> System.Collections.Generic.Stack<T> System.Collections.Generic.HashSet<T> System.Collections.Generic.LinkedList<T> System.Collections.Generic.EqualityComparer<T> System.Collections.Generic.Comparer<T> System.Collections.Generic.SortedDictionary<TKey, TValue>

System.Collections.Concurrent by: Microsoft

Provides several thread-safe collection classes that should be used in place of the corresponding types in the System.Collections.NonGeneric and System.Collections packages whenever multiple threads are accessing the collection concurrently.

System.Collections.NonGeneric by: Microsoft

Provides classes that define older non-generic collections of objects, such as lists, queues, hash tables and dictionaries. Developers should prefer the generic collections in the System.Collections package.

System.Collections.Specialized by: Microsoft

Provides older specialized non-generic collections; for example, a linked list dictionary, a bit vector, and collections that contain only strings. Commonly Used Types: System.Collections.Specialized.NameValueCollection System.Collections.Specialized.NameObjectCollectionBase System.Collections.Specialized.StringCollection System.Collections.Specialized.IOrderedDictionary System.Collections.Specialized.HybridDictionary System.Collections.Specialized.OrderedDictionary System.Collections.Specialized.ListDictionary System.Collections.Specialized.StringDictionary System.Collections.Specialized.BitVector32

System.ComponentModel by: Microsoft

Provides interfaces for the editing and change tracking of objects used as data sources. Commonly Used Types: System.ComponentModel.CancelEventArgs System.IServiceProvider System.ComponentModel.IEditableObject System.ComponentModel.IChangeTracking System.ComponentModel.IRevertibleChangeTracking

System.Composition by: Microsoft

This packages provides a version of the Managed Extensibility Framework (MEF) that is lightweight and specifically optimized for high throughput scenarios, such as the web. Commonly Used Types: System.Composition.ExportAttribute System.Composition.ImportAttribute System.Composition.Convention.ConventionBuilder System.Composition.Hosting.CompositionHost System.Composition.CompositionContext System.Composition.CompositionContextExtensions

System.Console by: Microsoft

Provides the System.Console class, which represents the standard input, output and error streams for console applications.

System.Data.Common by: Microsoft

Provides the base abstract classes, including System.Data.DbConnection and System.Data.DbCommand, for all data providers. Commonly Used Types: System.DBNull System.Data.Common.DbConnection System.Data.Common.DbException System.Data.Common.DbParameter System.Data.DbType System.Data.Common.DbDataReader System.Data.Common.DbCommand System.Data.Common.DbTransaction System.Data.Common.DbParameterCollection System.Data.Common.DbProviderFactory

System.Data.SQLite.Core by: SQLite Development Team

The official SQLite database engine for both x86 and x64 along with the ADO.NET provider.

System.Diagnostics.Debug by: Microsoft

Provides classes and attributes that allows basic interaction with a debugger. Commonly Used Types: System.Diagnostics.Debug System.Diagnostics.DebuggerStepThroughAttribute System.Diagnostics.Debugger System.Diagnostics.DebuggerDisplayAttribute System.Diagnostics.DebuggerBrowsableAttribute System.Diagnostics.DebuggerBrowsableState System.Diagnostics.DebuggerHiddenAttribute System.Diagnostics.DebuggerNonUserCodeAttribute System.Diagnostics.DebuggerTypeProxyAttribute

System.Diagnostics.FileVersionInfo by: Microsoft

Provides the System.Diagnostics.FileVersionInfo class, which allows access to Win32 version resource information for a physical file on disk. Commonly Used Types: System.Diagnostics.FileVersionInfo

System.Diagnostics.Process by: Microsoft

Provides the System.Diagnostics.Process class, which allows interaction with local and remote processes. Commonly Used Types: System.Diagnostics.Process System.Diagnostics.ProcessModule System.Diagnostics.ProcessStartInfo System.Diagnostics.ProcessThread

System.Diagnostics.Tools by: Microsoft

Provides attributes, such as GeneratedCodeAttribute and SuppresMessageAttribute, that are emitted or consumed by analysis tools. Commonly Used Types: System.CodeDom.Compiler.GeneratedCodeAttribute System.Diagnostics.CodeAnalysis.SuppressMessageAttribute

System.Dynamic.Runtime by: Microsoft

Provides classes and interfaces that support the Dynamic Language Runtime (DLR). Commonly Used Types: System.Runtime.CompilerServices.CallSite System.Runtime.CompilerServices.CallSite<T> System.Dynamic.IDynamicMetaObjectProvider System.Dynamic.DynamicMetaObject System.Dynamic.SetMemberBinder System.Dynamic.GetMemberBinder System.Dynamic.ExpandoObject System.Dynamic.DynamicObject System.Runtime.CompilerServices.CallSiteBinder System.Runtime.CompilerServices.ConditionalWeakTable<TKey, TValue>

System.Globalization by: Microsoft

Provides classes that define culture-related information, including language, country/region, calendars in use, format patterns for dates, currency, and numbers, and sort order for strings. Commonly Used Types: System.Globalization.DateTimeFormatInfo System.Globalization.CultureInfo System.Globalization.NumberFormatInfo System.Globalization.CalendarWeekRule System.Globalization.TextInfo System.Globalization.Calendar System.Globalization.CompareInfo System.Globalization.CompareOptions System.Globalization.UnicodeCategory

System.IO.FileSystem by: Microsoft

Provides types that allow reading and writing to files and types that provide basic file and directory support. Commonly Used Types: System.IO.FileStream System.IO.FileInfo System.IO.DirectoryInfo System.IO.FileSystemInfo System.IO.File System.IO.Directory System.IO.SearchOption System.IO.FileOptions

System.IO.FileSystem.Primitives by: Microsoft

Provides common enumerations and exceptions for path-based I/O libraries. Commonly Used Types: System.IO.DirectoryNotFoundException System.IO.FileAccess System.IO.FileLoadException System.IO.PathTooLongException System.IO.FileMode System.IO.FileShare System.IO.FileAttributes

System.Linq by: Microsoft

Provides classes and interfaces that supports queries that use Language-Integrated Query (LINQ). Commonly Used Types: System.Linq.Enumerable System.Linq.IGrouping<TKey, TElement> System.Linq.IOrderedEnumerable<TElement> System.Linq.ILookup<TKey, TElement> System.Linq.Lookup<TKey, TElement>

System.Linq.Async by: .NET Foundation and Contributors

Provides support for Language-Integrated Query (LINQ) over IAsyncEnumerable<T> sequences.