[Charny]

Hello, I made a little events/delegates example. I did it because I was bored and I decided to make it :P. I'm sharing it with you because events and delegates can be hard when your learn them and this example could help you.

I know, there's better way to divide, but I needed a subject for the example. So I took the division.

C#
Spoiler (Click to View)

Divison class (Division.cs)

Code

class Division
    {
  public delegate void EventHandler(Object sender, DivisionEventArgs e); //Delegate
  public event EventHandler DivisionDone; //This event will be executed when the divison will be done.
  public event EventHandler DivisionPerZero; //This event will be executed when the divisor is 0.

  public Division() //Constructor
  {
  }

  public void Divide(int dividend, int divisor)
  {
    if (divisor == 0)
    {
    if (DivisionPerZero != null)
    {
    DivisionPerZero(this, new DivisionEventArgs(dividend, divisor, 0.0)); //Execute the DivisionPerZero event
    return;
    }
    }

    double num = dividend/divisor;

    if(DivisionDone != null)
    {
    DivisionDone(this, new DivisionEventArgs(dividend, divisor, num)); //Execute the DivisionDone event
    }
  }
    }

    class DivisionEventArgs : EventArgs //The arguments of the division.
    {
  public DivisionEventArgs(int a, int b, double r)
  {
    dividend = a;
    divisor = b;
    result = r;
  }

  private int dividend;
  private int divisor;
  private double result;

  public int Dividend
  {
    get { return dividend; }
  }

  public int Divisor
  {
    get { return divisor; }
  }

  public double Result
  {
    get { return result; }
  }
    }

And you can use it like that :

Code

private void TESTING_METHOD()
{
    Division division = new Division();
    division.DivisionDone += new Division.EventHandler(div_DivisionDone);
    division.DivisionPerZero += new Division.EventHandler(div_DivisionPerZero);

    division.Divide(10, 5);
}

private void div_DivisionPerZero(object sender, DivisionEventArgs e)
{
    MessageBox.Show("Error! Division per zero!");
}

private void div_DivisionDone(object sender, DivisionEventArgs e)
{
    MessageBox.Show("Result : " + e.Result.ToString());
}

Visual Basic .NET
Spoiler (Click to View)

Division class (Division.cs)

Code

Class Division
    Public Delegate Sub EventHandler(sender As [Object], e As DivisionEventArgs)
    'Delegate
    Public Event DivisionDone As EventHandler
    'This event will be executed when the divison will be done.
    Public Event DivisionPerZero As EventHandler
    'This event will be executed when the divisor is 0.
    Public Sub New()
        'Constructor
    End Sub

    Public Sub Divide(dividend As Integer, divisor As Integer)
        If divisor = 0 Then
            If DivisionPerZero IsNot Nothing Then
                RaiseEvent DivisionPerZero(Me, New DivisionEventArgs(dividend, divisor, 0.0))
                'Execute the DivisionPerZero event
                Return
            End If
        End If

        Dim num As Double = dividend \ divisor

        RaiseEvent DivisionDone(Me, New DivisionEventArgs(dividend, divisor, num))
        'Execute the DivisionDone event
    End Sub
End Class

Class DivisionEventArgs
    Inherits EventArgs
    'The arguments of the division.
    Public Sub New(a As Integer, b As Integer, r As Double)
        m_dividend = a
        m_divisor = b
        m_result = r
    End Sub

    Private m_dividend As Integer
    Private m_divisor As Integer
    Private m_result As Double

    Public ReadOnly Property Dividend() As Integer
        Get
            Return m_dividend
        End Get
    End Property

    Public ReadOnly Property Divisor() As Integer
        Get
            Return m_divisor
        End Get
    End Property

    Public ReadOnly Property Result() As Double
        Get
            Return m_result
        End Get
    End Property
End Class

And you can use it like that :

Code

Private Sub TESTING_METHOD()
    Dim division As New Division()
    division.DivisionDone += New Division.EventHandler(AddressOf div_DivisionDone)
    division.DivisionPerZero += New Division.EventHandler(AddressOf div_DivisionPerZero)

    division.Divide(10, 5)
End Sub

Private Sub div_DivisionPerZero(sender As Object, e As DivisionEventArgs)
    MessageBox.Show("Error! Division per zero!")
End Sub

Private Sub div_DivisionDone(sender As Object, e As DivisionEventArgs)
    MessageBox.Show("Result : " + e.Result.ToString())
End Sub

Enjoy! If you have any questions, ask them here!

[CometJack]

That looks very confusing, can you comment a little please? Rated 5 stars :)

[xhtmlphp™]

That looks very confusing, can you comment a little please? Rated 5 stars :)

Ya, I think Charny should do an explanation on this :P

I don't understand Delegates, I've seen them being mentioned a few times but never understood the use of them :(

[Charny]

Ya, I think Charny should do an explanation on this :P

I don't understand Delegates, I've seen them being mentioned a few times but never understood the use of them :(

You can use delegates like that.. :

Code

public delegate void Write(string str);

  private void writeString(string str)
  {
    MessageBox.Show(str);
  }

  private void writeLength(string str)
  {
    MessageBox.Show(str.Length.ToString());
  }

  private void TestDelegate()
  {
    Write write = new Write(writeString);
    write += new Write(writeLength);

    write("test");
  }

Try this code and check the result, then you can play with the code ;).

[CometJack]

I get the delegate's but I don't get how you make your own event handler :(

[Charny]

I get the delegate's but I don't get how you make your own event handler :(

Read some events tutorials, you will learn it ;).

[Charny]

A little buump! 😁

[enacje]

this is hard to learn but harder to explain it :P I can make them but I can't explain how and what lol

[Charny]

this is hard to learn but harder to explain it :P I can make them but I can't explain how and what lol

Haha, same for me 😝. That's why I didn't really gave informations on them.

[Charny]

A little bump for my post :D!

[laptopguy]

Nice one Charny. People who call themselves programmers and don't understand this type of shit aren't tbh. And why was the thread allowed to die ? This is one of those things in this section that is actually useful, like the things Vorfin and Deathader post sometimes.

[Charny]

Nice one Charny. People who call themselves programmers and don't understand this type of shit aren't tbh. And why was the thread allowed to die ? This is one of those things in this section that is actually useful, like the things Vorfin and Deathader post sometimes.

Thanks, and why is this thread dieing? Because most 'coders' here doesn't bother learning delegates & events because their IDE does everything for them..

(Sorry if it didn't make sense <.<)

[Charny]

Bumppp! I'll do another example soon :).

[killerdoob420]

very nice i couldnt have explained it better

[Charny]

very nice i couldnt have explained it better

Thanks for the comment 😁!