Understanding Delegates

Delegates are of two types 

1. Normal delegates 
2. Generic delegates

1:Normal delegates - These delegates again will fall into three ways of writing it or using it

1. Simple delegates
2. Anonymous delegates
3. Lambda delegates

Simple delegates - these are delegates who are called in a normal way. 

1. Declare delegate
2. Define the method which will match the declared delegate
3. Inside the Main method - 

- Create object of delegate with method name in its constructor
- Invoke delegate : Pass parameters if any inside the object of delegate similar to method.
- Print the values if needed 

Anonymous delegates: These are very similar to normal delegates. The only difference is that the method definition is given directly inside the delegate's constructor with the DELEGATE keyword.

Lambda delegate - This is also similar to simple delegates. The difference is that here we are not creating a delegate object by using the “new” keyword instead we use the object reference of delegate and use lambda operator => to point only to statements of the method without using the return keyword (note there is no method name here). Later invoke delegate reference like a method.

2:Generic Delegates - used to further minimize the code of lambda expression. Here we don't need to declare a delegate declaration

1.Func Delegate - It is a read made delegate with return values i.e Lambda + Func

2. Action Delegate - It is a read made delegate with no return values i.e return void [we are not expecting any return value] i.e Lambda + Action. Action has only input variable and prints or calculates something by taking input variable. This will not return any value.

3: Predicate Delegates - It is an extension of FUNC delegate. This will always returns Boolean type

               /*

* predicate is an extension for FUNC. It is used for checking purpose ex: you just want to check the return type is true or false. 

* It always return type is boolean.

*Overall if you see, we can make use of FUNC delegate only for returning boolean type. 

*There is no need of predicate delegate. So we can avoid Predicate delegate

*/

static void Main(string[] args)

{

Predicate<string> predicateObj = x => x.Length > 5;

List<string> listObj = new List<string>();

listObj.Add("Shiv");

listObj.Add("SureshMarla");

string result = listObj.Find(predicateObj);

Console.WriteLine(result);

Console.ReadLine();

}