Value Type (where T : struct)

The built-in primitive data types, such as char, int, and float, as well as user-defined types declared with struct, or enum. Their default value is new T() :

default(int)            // 0
default(DateTime)       // 0001-01-01 12:00:00 AM
default(char)           // '\\0' This is the "null character", not a zero or a line break.
default(Guid)           // 00000000-0000-0000-0000-000000000000
default(MyStruct)       // new MyStruct()

// Note: default of an enum is 0, and not the first *key* in that enum
// so it could potentially fail the Enum.IsDefined test
default(MyEnum)         // (MyEnum)0

Reference Type (where T : class)

Any class, interface, array or delegate type. Their default value is null :

default(object)         // null
default(string)         // null
default(MyClass)        // null
default(IDisposable)    // null
default(dynamic)        // null