System Namespace

Contains fundamental classes and base types that define value types, reference types, exceptions, and the methods that are common to all objects. The System namespace is available in all .NET projects.

Classes

public class Object

Provides functionality for all classes, such as the base class of the .NET Framework object hierarchy, the clone, hash code, equality comparison, type name, and string representation of an object.

public abstract class ValueType : Object

Provides a base class for value types that are created by users.

public abstract class Exception

Represents errors that occur during runtime.

public sealed class String : ValueType, IEnumerable<Char>, ICollection<Char>, ISequenceEquals, IComparable, IComparable<String>, IQuotable<String>, IStringComparable, IParsable<String>

Represents a text string.

public static class Console

Represents the standard input, output, and error streams for console applications.

public struct DateTime : ValueType, IComparable, IComparable<DateTime>, IDateAndTime, ISpanFormattable, IParsable<DateTime>

Represents an instance of a date and time, expressed as a value.

public static class Math

Provides constants and instance methods for trigonometric, logarithmic, and other common mathematical functions.

public struct Guid : ValueType, IComparable, IComparable<Guid>, IIdempotent, IParsable<Guid>, IStringComparable

Represents a globally unique identifier (GUID), which is a 128-bit value.

public abstract class Type : MemberInfo, IStringFormattable, IStringConvertible

Represents type declarations, such as class, interface, or value types. Type information is encapsulated by Type objects.

Interfaces

public interface ICollection<T> : IEnumerable<T>, IEnumerable

Represents a collection of objects.

public interface IList<T> : ICollection<T>

Represents a strongly typed list of objects that can be accessed by index.

public delegate void Action

Encapsulates a method that has no parameters and does not return a value.