Single Object Instance without static

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Hi I know i am lazy but just to check if there is any better ideas around.
I had an event in a usercontrol

C#

public event EventHandler EH_OpenDefaultClick;

A form when a radio button is click will subscribe to this event. However this form will not be destroyed and whenever the radio button is click, i will subscribe to the event

C#

ucStdButton_Recipe.EH_OpenDefaultClick += ucStdButton_Recipe_EH_OpenDefaultClick;

with the only line above, every time it will be subscribe, hence triggering multiple time. I can add in the code to compare if it is null. But eventually codes get untidy with all these == null

C#

if (ucStdButton_Recipe.EH_OpenDefaultClick == null)
    ucStdButton_Recipe.EH_OpenDefaultClick += ucStdButton_Recipe_EH_OpenDefaultClick;

I cannot declare the event as static as the event is subscribe during runtime. Is there any declaration type allowing me to subscribe more easily without the comparison statement

Posted 18-Jan-16 21:59pm

ishtarsg

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Andy Lanng · Answer 1 · 2016-01-18T22:08:00

Solution 1

You can check for a specific handler subscription:

C#

public bool IsHandlerSubbed(Delegate handler)
{   
	if ( this.EventHandler != null )
	{
		foreach ( Delegate h in this.EventHandler.GetInvocationList() )
		{
			if ( h == handler)
			{
				return true;
			}
		}
	}
	return false;
}

Posted 18-Jan-16 22:08pm

Andy Lanng

Leo Chapiro · Answer 2 · 2016-01-18T22:13:00

Solution 2

You can prevent it by unsubscribing before adding it:

C#

ucStdButton_Recipe.EH_OpenDefaultClick -= ucStdButton_Recipe_EH_OpenDefaultClick;
ucStdButton_Recipe.EH_OpenDefaultClick += ucStdButton_Recipe_EH_OpenDefaultClick;

Posted 18-Jan-16 22:13pm

Leo Chapiro