Check if an event already exists

Question

I have a data grid loading row event

_gridObj.LoadingRow += new EventHandler<DataGridRowEventArgs>(_gridObj_LoadingRow);

and in the handler I am creating another event. In the following code how can I know if the MouseLeftBtn event already exists for that row?

void _gridObj_LoadingRow(object sender, DataGridRowEventArgs e)
{
    e.Row.MouseLeftButtonUp += new MouseButtonEventHandler(Row_MouseLeftButtonUp);
}

Thanks,

Voodoo

Do you want to test that an event handler is attached so you don't attach more than one event? i.e the LoadingRow event might get fired more than once per row? — aqwert, Sep 27 '10 at 01:11
Yes, in the `_gridObj_LoadingRow` the `MouseLeftButtonUp` event is attached multiple times. I want to check whether the `MouseLeftButtonUp` event is already attached so I don't register another event for it. It is firing the `MouseLeftButtonUp` multiple times in my case here. — VoodooChild, Sep 27 '10 at 03:26
Ok, I have added an answer which should meet your requirements. — aqwert, Sep 27 '10 at 04:39

score 15 · Accepted Answer · answered Sep 27 '10 at 04:38

Based on your comment that you don't want to attach muliple handlers in this case I unsubscribe then resubscribe. It does not give an error unsubscribing if none exists and ensures only one handler.

void _gridObj_LoadingRow(object sender, DataGridRowEventArgs e)
{
    e.Row.MouseLeftButtonUp -= new MouseButtonEventHandler(Row_MouseLeftButtonUp);
    e.Row.MouseLeftButtonUp += new MouseButtonEventHandler(Row_MouseLeftButtonUp);
}

Check if an event already exists

1 Answers1

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