The usage of delegate

Question

i saw that delegate is used for custom events. as far example

delegate string FuncRef(string Val);

FuncRef fValue = GetFieldName;

fValue("hello");

what i do here just declare delegate and assign a function name to delegate and call like fValue("hello"); whenever it is required.

instead of calling the GetFieldName() through delegate i can call it directly. so i just want to know why should i use delegate to call function where as we can call function directly....what is the advantage of calling any function through delegate.

so please tell me in what kind of scenario delegate usage is required except event handling. please guide me with sample code and simulate a situation where i need to call function through delegate except event handling. please show me some real life scenario where we have to call function through delegate.

Answer 1

The reason to use delegates instead of calling the function directly is the same reason you do

var taxRate = 0.15;
var taxAmount = income * taxRate;

instead of

var taxAmount = income * 0.15;

In other words: using a variable to hold a reference to a callable entity (a delegate is exactly that) allows you to write code that can change its behavior depending on the parameters passed to it (the value of the delagate we 're passing in). This means more flexible code.

For examples of code that uses delegates you can look at LINQ (of course), but there's also the "delegates 101" example which is relevant in any language: filtering a list.

Answer 2

delegate string FuncRef(string Val);

FuncRef fValue;   // class member

if (condition1)
    fValue = GetFieldName1;
else if (condition2)
    fValue = GetFieldName2;
else
    fValue = GetFieldName3;

// Another function
fValue("hello");