What are the advantages of delegates? [duplicate]

Answer 1

Delegates serve three purposes:

1. A simplified implementation of the Observer pattern
2. A simplified implementation of callbacks
3. Anonymous (non-reusable) blocks of code

Observer

public class Something
{
    public event EventHandler SomethingHappened;
}

public class SomethingConsumer
{
    private mySomething = new Something();

    public void WireUpEvents()
    {
        mySomething.SomethingHappened += whenSomethingHappened;
    }

    private void whenSoemthingHappened(object sender, EventArgs e)
    {
        // do something
    }
}

CallBack

public void DoSomethingAsynchronously(EventHandler callBack)
{
    // long running logic.
    callBack(this, EventArgs.Empty);
}

Anonymous non-reusable code

public void DoSomethingReusably(Action nonReusableCode)
{
    // reusable code
    nonReusableCode();
    // more reusable code
}

public void DoALotOfSomething()
{
    DoSomethingReusably(() => { /* non-reusable code here */ });
    DoSomethingReusably(() => { /* non-reusable code here */ });
    DoSomethingReusably(() => { /* non-reusable code here */ });
}

In all cases, it's just a matter of providing conciceness.