Doubt about events: How to notify me when a variable that begins with the value 300, drops with a while loop to 10, but when reaches 30, the event raises.

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Hi everyone. I am newly programmer of C# (junior) and I have run into a problem that I don't really know how to tackle. Although I have a notion on how the resolution has to be like:

C#

/*
I want to create a program that through the use of events, it will notify me when a variable (int) is under the value of 30, the event raises and shows "Console.WriteLine()" showing that the variable has dropped to a low value.
In order to decrease the value of the variable (which I refer to as "i") I use a while loop.
*/
{
// Inside main
int i = 300;
while(i  > 10)
{
          i--;
}
// Event code to implement.

I have a slight idea about how events work but I don't really yet understand how to create them from scratch. If any charitable soul is willing to help me i'd be grateful.

Posted 18-Jul-12 0:57am

unscathed18

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dimpledevani 18-Jul-12 6:59am

Create a normal event, in your loop when you are decrementing the value of 'i' , then you can check if its 30 and if yes , you can call the event like you call methods from there

Erik Rude 18-Jul-12 7:09am

You could make your integer i a member of a class. That class could have an event that is raised when the value of i is low.

ArtificerGM 18-Jul-12 7:20am

A charitable soul helped before you asked!

unscathed18 18-Jul-12 7:46am

Yes, that's right. I'll try to get the hang out of it, but first I have to understand how it works.

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lukeer · Accepted Answer · 2012-07-18T01:29:00

First version: just the console output:

C#

private static int Main()
{
    for( int i = 300; i > 10; i--)
    {
        if( i < 30)
        {
            Console.WriteLine("Value is below 30.");
        }
    }
}

But you actually wanted to create an event

C#

public class MyClass
{
    // Define custom event
    public event EventHandler ValueLow;

    public void DoSomething()
    {
        for( int i = 300; i > 10; i--)
        {
            if( i < 30)
            {
                EventHandler eh = ValueLow;
                if( eh != null)
                {
                    // Fire custom event
                    eh(this, new EventArgs());
                }
            }
        }
    }
}

private static int Main()
{
    MyClass myClass = new MyClass();

    // Subscribe to custom event
    myClass.ValueLow += new EventHandler(MyClass_ValueLow);

    // Handle custom event
    private void MyClass_ValueLow(object sender, EventArgs e)
    {
        Console.WriteLine("Value is low.");
    }
}

You can actually transport valueable data within events.

C#

public class MyClass
{
    // Define custom event
    public delegate void ValueLowEventHandler(int value, int threshold);
    public event ValueLowEventHandler ValueLow;

    public void DoSomething()
    {
        for( int i = 300; i > 10; i--)
        {
            if( i < 30)
            {
                EventHandler eh = ValueLow;
                if( eh != null)
                {
                    // Fire custom event
                    eh(i, 30);
                }
            }
        }
    }
}

private static int Main()
{
    MyClass myClass = new MyClass();

    // Subscribe to custom event
    myClass.ValueLow += new ValueLowEventHandler(MyClass_ValueLow);

    // Handle custom event
    private void MyClass_ValueLow(int value, int threshold)
    {
        Console.WriteLine("Value is " + value.ToString() + " which is below " + threshold.ToString() + ".");
    }
}