static void Delegate_Example_3()
{
// An example of a Regular Method; Anonymous Method, and Lambda Delegates
// Which are all the same.
Console.WriteLine("Delegate Example 3 - Showing Different/Same Delegates ");
GenericExamples.Same_Main();
Console.ReadKey();
}
public static void Menu()
{
int x = 0;
do
{
/*
* Interfaces Implement Polymorphism. Each class that Inherits an Interfaces will implement
* the method defined in the interface in a different way, making it Polymorphic.
* Interfaces make it easier to make code easier to maintain,extend, and test.
* When a class implements an Interface, it fufills a contract set by the Interface.
*
* See Generic Examples also
*
* Interfaces should be programmed at the right level. Interfaces should be granular
* IList<T> - ICollection -> IENumberable
*
* IEnumerable Implementations (IEnumerable<T> limited to collectsions that are strongly typed:
* List<T>
* Array
* ArrayList
* SortedList<TKey, TValue>
* HashTable
* Queue / Queue<T>
* Stack / Stack<T>
* Dictionary<TKey, TValue>
* ObservableCollection<T>
*
* ICollection<T> Implementations
* List<T>
* SortedList<TKey, TValue>
* Dictionary<TKey, TValue>
*
* IList<T> Implementations
* List<T>
*
* Program at the Right Level
* IEnumerable <T> - If we need to Iterate over a Collection / Sequence or Data Bind
* to a List Control
* ICollection<T> - If we need to Add/Remove Items in a Collection,
* Count Items in a Collection,
* Clear a Collection.
* IList<T> - If we need to Control the Order Items in a Collection,
* Get an Item by the Index.
*
* Differences between IEnumerable, ICollection, and IList Interfaces
* https://www.c-sharpcorner.com/UploadFile/78607b/difference-between-ienumerable-icollection-and-ilist-interf/
*
* Abstract Classes versus Interfaces
* ------------------------- | ---------------------
* May Contain implementation | May not contain implementation code - Biggest weakness
* Code or may simulate an | By default all objects are public and absract. Since it is
* interface and just have | abstract by default then all methods must be implemented.
* abstract signature. |
* A class may inherit from a | A class may implement any number of interfaces - Biggest
* single base class | strength.
* Members have access | Members are automatically public
* modifiers
* May contain fields, | May only contain properties, methods, events, and indexers .
| No implementation usually just contain signatures.
| properties, constructors, |
| destructors, methods, | Interfaces may not contain fields
| events, and indexers |
|
| Note: You can use interface when you know signature but you don't know the implmentation.
| You can use abstract class when you know some implementation but not all. A class may only
| inherit from one abstract class, but a class may inherit from multiple interfaces. See
| info on Abstract Methods in BaseExamples.cs
|
| Note_2: Interfaces can't have static methods. A class that implements an interface needs
| to implement them all as instance methods.
|
| As a guideline:
| Use classes and subclasses for types that naturally share an implementation
| Use interfaces for types that have independent implementations.
|
| Natural - Can Compare with other Instances of the same type
|
| EQUALITY COMPARISONS
| Natural IEquatable<T> IComparable<T>
| IComparable
| Plugged_in IEqualityComparer IComparer
| IEqualityComparer<T> IComparer<T>
| Structural IStructuralEquatable IStructuralEquatable
|
|
|
|
*/
Console.Clear();
Console.WriteLine(" Types of Interfaces \n ");
Console.WriteLine(" 0. IComparable \n ");
Console.WriteLine(" 1. IDisposable \n ");
Console.WriteLine(" 2. IEnumerable \n ");
Console.WriteLine(" 3. IList \n");
Console.WriteLine(" 4. IDictionary \n");
Console.WriteLine(" 5. Self Created \n");
Console.WriteLine(" 6. IQueryable \n");
Console.WriteLine(" 8. Web Page \n");
Console.WriteLine(" 9. Quit \n\n ");
Console.Write(" Enter Number to execute Routine ");
int selection;
selection = Common.readInt("Enter Number to Execute Routine : ", 0, 9);
switch (selection)
{
case 0:
/*
* IComparable will allow you to compare one class( one instance) to another
* class (or instance). You have to implement 'compare' in class that is
* inheriting IComparable.
*
* IComparable will tell you if
* x < y
* x > y
* x == y
* returning an integer
* - 1 means less than
* 1 means greater
* 0 means equal to
*
*/
SortingExamples.Sort_A_Class();
Console.ReadKey();
SortingExamples.Sort_Numbers();
Console.ReadKey();
break;
// ==, != operators - Work out of the box only for primitive types and reference types
// Operators do not work in generic code
// Object.Equals - ok in generic code
//
// >, <, >=, <= operators - Work out of the box only for primitive types
//
case 2:
/*
* When something is define as IEnumerable it lets you know that you can use
* LINQ to Query.
*
* IEnumerable - A List, Array, Query, String implements IEnumerable.
* An IEnumerable Interface specifies that the underlying type implements IEnumerable
*
* public Interface IEnumerator
* {
***
*** MoveNext will throw an exception if collection has changed.
*** Cannot modify a collection while enumerating.
***
***
*** bool MoveNext();
*** object Current {get;}
*** void Reset();
***}
***
***public interface IEnumerable
***{
***IEnumerator GetEnumerator();
***}
***
**
** You can implement a class that uses the IEnumerable<string> interface. If you do this
** you will have to use the 'yield return'
** 'yield return' statements are NOT Return statements.
**
** What happens when a yield return occurs inside a method that returns an IEnumerator interface
** The C# compiler determines this is a case where you want the compiler to write an enumerator for
** you. The yield return statements simply tell the compiler what the sequence of enumeration values
** to return is.
*
** Use 'yield return' when you want to return elements from a collection one at a time. Once
* execution goes back it will pick up execution at the statement immediately following
* the 'yield' return.
*
*
* See also IterationStatements.cs for examples of Yield Return.
* See also LINQExamples.cs on how deferred execution works.
*
*
*
*/
MenuCreateAndUseTypes.EnumerableMethods.Menu();
MenuCreateAndUseTypes.IEnumeratorInterface.Menu();
break;
case 3:
// See BaseExamples.cs on more info on Array versus Lists
//
// IList<T>
// Arrays are a fixed size. System.Array does not contain a definition for 'Add'
// new string[] is a fixed size.
// This problem with arrays is what List<T> was designed to overcome.
// new List<string> allows you to add to an array.
// Arrays can be multi-dimensional. List are restricted to being one dimensional.
//
// List<T> acts as an array in every aspect and in addition you can add and
// remove elements.
//
// List<T> uses a capacity and a count method
// Capacity - Gets increased if you keep adding elements. Once you add elements
// and go past the capacity it gets increased by 8.
//
// count - Total number of elements you have added
// if the count is 4 and the capacity is 8 you cannot display elements that exceed the count.
//
GenericExamples.GA_Main();
break;
//case 4:
//Dictionary uses a hash table. It is a large collection
//that will divide a collection into smaller collections.
//Each smaller collection is defined as a bucket.
//If you know what bucket the item your searching for is in,
//you only need to search that bucket.
//
//The modulo % method along with the .gethashcode method is used to determine the bucket when
//storing or retrieving a value.
//
//If two values x and y evaluate to equal then they must evaluate to the same hash code.
//
// StringComparer implements IEqualityComparer
// If two objects are equal they must return the same hash code that is why the IEqualityComparer
// defines its own get hash code method so you can make sure that rule is followed.
//
// public int GetHashCode (string obj)
// {
// return obj.ToUpper().GetHashCode(); // Best to reuse what Microsoft has already done
// }
//
// SortedList<TKey, TValue> - Dictionary that keeps its values sorted. It's a Dictionary and NOT a List.
// Sorted List does NOT contain a Hash Table. So when you implement an IComparer interface you won't have a
// hash method.
//
// SortedDictionary<TKey, TValue> - Functionally is the same as SortedList<TKey, TValue>
// Added and Removing Elments is a lot faster using a Sorted Dictionary verus a Sorted List.
// So only use a SortedDictionary if you need to make frequent changes to the collection.
//
case 5:
Shape shape = new Oval();
shape.WhatAmI();
var car = new Car();
car.Start();
car.Stop();
var mower = new LawnMower();
mower.Start();
mower.Stop();
Console.Write("\nPress Enter to Continue ");
Console.ReadKey();
Collections.
Using_Collections();
Console.ReadKey();
break;
case 6:
/* IQueryable is used in Entity Frameworks and serves as a replacement for IEnumerable. It is how
* a database is accessed via SQL. Like IEnumerable it represents a datasource something you can query.
* IQueryable does not execute code in memory. IQueryable translates code into SQL. IQueryable works
* with the Expression clause. The Expression Clause will translate Lambda statements and passes them
* so that they can be translated into SQL. The Entity Framework will inspect the Expression to tranlate
* into SQL.
*
* Watch this video again at some point to write program that will use Entity Frameworks and display
* SQL to Console.
* https://app.pluralsight.com/course-player?clipId=64018007-2730-4598-9fca-6aee3d4e0fcd
*/
Console.WriteLine(" Not yet built");
Console.ReadKey();
break;
case 8:
Process.Start("http://msdn.microsoft.com/en-us/library/87d83y5b.aspx");
break;
case 9: x = 9;
break;
default: Console.WriteLine(" Invalid Number");
break;
}
} while (x < 9); // end do
} // end Menu()
public static void Menu()
{
int x = 0;
do
{
Console.Clear();
Console.WriteLine(" Create Types \r ");
Console.WriteLine(" Create value types (structs, enum), refererence types, generic types, \r");
Console.WriteLine(" constructors, static variables, methods, classes, extension methods, \r");
Console.WriteLine(" optional and named parameters, and indexed properties; create \r");
Console.WriteLine(" overloaded and overridden methods \n");
Console.WriteLine(" 0. Value Types (Immutable) \n ");
Console.WriteLine(" 1. Generic Types \n ");
Console.WriteLine(" 2. Nulls \n ");
Console.WriteLine(" 3. Static Variables \n ");
Console.WriteLine(" 4. Extension Methods\n ");
Console.WriteLine(" 5. Optional/Named/Out Parameters \n ");
Console.WriteLine(" 6. Methods \n");
Console.WriteLine(" 7. Indexers \n");
Console.WriteLine(" 8. Reference Types (Mutable) (Can be boxed) \n");
Console.WriteLine(" 9. Quit \n\n ");
int selection;
selection = Common.readInt("Enter Number to Execute Routine : ", 0, 9);
switch (selection)
{
case 0: ValueTypes.Menu();
break;
case 1: GenericExamples.PrimaryMain();
DynamicExamples.DMain();
break;
case 2: Nulls.Menu();
break;
case 3: StaticExamples.Menu();
Console.ReadKey();
break;
case 4:
/* Extension Methods
* - Extend types without altering them. Escpecially useful for extending types that are not
* yours or are sealed.
* - They are declared as static in a static class
* - The first paramter has the 'this' modifier
* - The first parameter's type is the type being extended
*
* Both the class and the method have to be static
* The type that your extending goes into the signature as the first argument with the 'this' keyword
*/
EnumerableMethods.Menu();
break;
case 5:
/* Optional/Named/Out Parameters
*
* ***************************************************************************************
* Optional Parameters
* There are 4 ways that can be used to make method parameters optional
* 1. Use parameter arrays - Can have 0 or 1,2,3,... parameters.
* 2. Method overloading
* 3. Specify parameter defaults
* 4. Use OptionalAttribute that is present in System.Runtime.InteropServices namespace
*
* Please note - A parameter array must be the last parameter in a formal parameter list.
*
* 1. Parameter arrays
*
* AddNumbers(10,20) <-- 3 or more paramters optional
* AddNumbers(10,20, new object[] {30,40,50});
* public static void AddNumbers( int firstNumber, int secondNumber, params object[] resetofNumbers)
*
* params must be last parameter - below will get comile error
* public static void AddNumbers( int firstNumber, params object[] resetofNumbers, int secondNumber)
* https://www.youtube.com/watch?v=jbtjGii300k&index=67&list=PLAC325451207E3105
*
* 2. Method OverLoading
*
* AddNumber(10,20) <-- Will give error, since you must provide 3 or more paramters.
* AddNumber(10,20,null) <-- will work without error
* public static void AddNumbers(int firstNumber, int secondNumber, int[] restofNumbers)
*
* AddNumber(10,20) <-- Will work with the below method overload
* public static void AddNumbers(int firstNumber, int secondNumber)
* {
* AddNumbers(fistNumber, secondNumber, null);
* }
* public static void AddNumbers(int firstNumber, int secondNumber, int[] restOfNumbers)
* {
* }
*
* https://www.youtube.com/watch?v=khcOI3-Kh84&index=68&list=PLAC325451207E3105
*
* 3. Specifying parameter defaults - If we don't supply the third parameter then it
* will take the default assigned). Optional parameters should always be placed as
* the last parameter(s).
*
* AddNumbers(10,20); <-- 3rd parameter will take default of null.
* AddNumbers(10, 20, new int[] {30, 40}); <-- will use 30, 40 as 3rd and 4th parameters.
* public static void AddNumbers(int firstNumber, int secondNumber, int[] restofNumbers = null)
*
*
* https://www.youtube.com/watch?v=Dmycz0ro1Yc&index=69&list=PLAC325451207E3105
*
* 4. Optional Attribute - Present in System.Runtime.InteropServices namespace
*
* using System.Runtime.InteropServices
* AddNumbers(10,20);
* public static void AddNumbers(int firstNumber, int secondNumber, [Optional] restofNumbers)
*
* *
* https://www.youtube.com/watch?v=p_9f5SSXxLw&list=PLAC325451207E3105&index=70
*
*
* ***************************************************************************************
* Named Parameters
* You don't have to specify the type. The name and type is attained from the
* calling method. You don't have to worry about the order, since the parameters
* are named it is smart enough to figure them out regardless of the order.
*
* Sample
* var customer = new Customer();
* var order = new Order();
* var payment = new Payment();
* orderController.PlaceOrder
* (customer, order, payment, allowSplitOrders:true, emailReceipt:false)
*
* **************************************************************************************
* Out Parameters
* The 'out' keyword causes arguments to be passed by reference. This is like
* the 'ref' keyword, except that the ref requires that the variable be
* initialized before it is passed.
*
* To use both the ref and out parameter, both the
* method definition and the calling method must explicitly use the
* ref or out keyword
*
* In general ref parameters are not recommended. Ref parameters are not intuitive, why did you have
* to pass an empty string (assuming you initialized with empty string). Ref parameters make the code
* harder to understand.
*
* Out Parameters are also not recommeneded. Even though you don't have to initialize, they too are
* not intutive. They also make the method harder to understand.
*
* Tuples is a data structure that allows for the use of multiple
* elements. The .Net framework class does not represent a tuple but rather provides methods for
* creating tuples.
*
* Tuple is a nice way to group a set of data and pass it out. However it is very clumbsy to work with
* and it not intuitive at all in what is being returned.
*
* So since Ref, out, and Tuples are not intuitive. Is there a better way to return parameters. Yes
* and it will through objects. An 'object' can readily be returned from a method. You can often
* define a class just for return values. The term 'object' refers to the instance of a standardized
* class. The class is usually defined with a 'get' and 'set' properties.
*
*/
RunwithOutput();
break;
case 6: Methods.Menu();
break;
case 7:
ExamLibrary.CreateAndUseTypes.Indexer.Menu();
Console.ReadKey();
break;
case 8: ReferenceTypes.Menu();
Console.ReadKey();
break;
case 9: x = 9;
break;
default: Console.WriteLine(" Invalid Number");
break;
}
} while (x < 9);
}