C# Action in Foreach

Question

fMethod is an Action<Fruit>.

But when fMethod is called, the parameter is always the last entry of _Fruits.
How to solve this?

foreach(Fruit f in _Fruits)
{
   field.Add(new Element(f.ToString(),delegate{fMethod(f);}));
}

possible duplicate of [Is there a reason for C#'s reuse of the variable in a foreach?](http://stackoverflow.com/questions/8898925/is-there-a-reason-for-cs-reuse-of-the-variable-in-a-foreach) — Joey, Mar 31 '13 at 12:10

Sergey Kalinichenko · Accepted Answer · 2013-03-31T12:22:27.000

10

This is a well-known problem of using a modified clause in a call that creates a delegate. Adding a temporary variable should solve it:

foreach(Fruit f in _Fruits)
{
    Fruit tmp = f;
    field.Add(new Element(f.ToString(),delegate{fMethod(tmp);}));
}

This problem is fixed in C# 5 (see Eric Lippert's blog).

edited Mar 31 '13 at 12:22

answered Mar 31 '13 at 12:10

3

This issue **is** fixed in C# 5.0: http://blogs.msdn.com/b/ericlippert/archive/2009/11/12/closing-over-the-loop-variable-considered-harmful.aspx – DasKrümelmonster Mar 31 '13 at 12:15
@DasKrümelmonster That's very nice to know, thank you very much! – Sergey Kalinichenko Mar 31 '13 at 12:22

score 1 · Answer 2 · answered Mar 31 '13 at 12:10

1

Try using a temp variable.

foreach(Fruit f in _Fruits)
{
   var temp = f;
   field.Add(new Element(temp.ToString(),delegate{fMethod(temp);}));
}

answered Mar 31 '13 at 12:10

scartag

2 Answers2