Question

hi I am trying to write an lambda for an event handler. so I can provide more information to the method that gets called.

so I am doing:

button.Click+=new EventHandler ((object sender, EventArgs args) => 
{ button_click (i, sender, args); });

where:

public void button_click (int i, object sender, EventArgs eventArgs)

ok so this works as in the method get called, but i is always the last known value of i, I really want the value at the point where the lambda is pass to the event. How do you do that?

thanks

Answer 1

Just create a copy of the variable:

int currentI = i;
button.Click+=new EventHandler ((object sender, EventArgs args) => 
    { button_click (currentI, sender, args); });

Note that you’ve got a certain amount of cruft there. You can write it more simply as:

int currentI = i;
button.Click += (sender, args) => button_click(currentI, sender, args);

Personally I’d rename the button_click method to conform with .NET naming conventions though.