how to clear event handles in c#

Question

I'm using global variable named "client"

For example

client.getPagesCompleted += (s, ee) =>
{
    pages = ee.Result;
    BuildPages(tvPages.Items, 0);
    wait.Close();
};
client.getPagesAsync(cat.MainCategoryID);

I need to clear handlers for getPagesCompleted and set another handler.
How to easy clear handles?
I know client.getPagesCompleted-=new EventHandler(...). But it is very difficult. I need easy way. I'm using client.getPagesCompleted=null but error shown. "only use += / -+"

Answer 1

Save the event object to a variable, and use -= to unsubscribe.

Answer 2

The only way to remove an event handler is to use the -= construct with the same handler as you added via +=.

If you need to add and remove the handler then you need to code it in a named method rather using an anonymous method/delegate.

Answer 3

You don't have to put your event handler in a separate method; you can still use your lambda function, but you need to assign it to a delegate variable. Something like:

MyEventHandler handler = (s, ee) => 
{ 
    pages = ee.Result; 
    BuildPages(tvPages.Items, 0); 
    wait.Close(); 
}; 

client.getPagesCompleted += handler; // Add event handler
// ...
client.getPagesCompleted -= handler; // Remove event handler