Collections and Generics

1. Interface layout

2. the .NET platform supports two broad groups of data types, termed value types and reference types. C# provides a very simple mechanism, termed boxing, to convert a value type to a reference
type.

 

3. In summary, generic containers provide the following benefits over their nongeneric counterparts:
• Generics provide better performance, as they do not result in boxing or unboxing penalties.
• Generics are more type safe, as they can only contain the “type of type” you specify.
• Generics greatly reduce the need to build custom collection types, as the base class library provides several prefabricated containers.

 

4. With the introduction of generics, the C# default keyword has been given a dual identity. In addition to its use within a switch construct, it can be used to set a type parameter to its default value. This is clearly helpful given that a generic type does not know the actual placeholders up front and therefore cannot safely assume what the default value will be. The defaults for a type parameter are as follows:
• Numeric values have a default value of 0.
• Reference types have a default value of null.
• Fields of a structure are set to 0 (for value types) or null (for reference types).

// The "default" keyword is overloaded in C#.
// When used with generics, it represents the default
// value of a type parameter.
public void ResetPoint()
{
    xPos = default(T);
    yPos = default(T);
}

 

5.

// MyGenericClass derives from Object, while
// contained items must have a default ctor.
public class MyGenericClass<T> where T : new()
{...}
// MyGenericClass derives from Object, while
// contained items must be a class implementing IDrawable
// and support a default ctor.
public class MyGenericClass<T> where T : class, IDrawable, new()
{...}
// MyGenericClass derives from MyBase and implements ISomeInterface,
// while the contained items must be structures.
public class MyGenericClass<T> : MyBase, ISomeInterface where T : struct
{...}
// <K> must have a default ctor, while <T> must
// implement the generic IComparable interface.
public class MyGenericClass<K, T> where K : new()
where T : IComparable<T>
{...}