How do I fix: Access to foreach variable in closure resharper warning?

Question

I'm getting this ReSharper warning: Access to foreach variable in closure. May have different behaviour when compiled with different versions of compiler.

This is what I'm doing:

@foreach(var item in Model)
{
    // Warning underlines "item".
    <div>@Html.DisplayBooleanFor(modelItem => item.BooleanField)</div>
}

My extension is as follows:

public static MvcHtmlString DisplayBooleanFor<TModel, TValue>(
    this HtmlHelper<TModel> helper, 
    Expression<Func<TModel, TValue>> expression)
{
    bool value;

    try
    {
        var compiled = expression.Compile()(helper.ViewData.Model);
        value = Convert.ToBoolean(compiled);
    }
    catch (Exception)
    {
        value = false;
    }

    return MvcHtmlString.Create(value ? "Yes" : "No");
}

Note this is working as expected but how can I avoid this warning?
I'll appreciate any help provided.

Why are you using `Expression<>` if all you do with it is call `.Compile()` on it? Why not use `Func<>` directly? — , Sep 22 '12 at 19:45
Why are you passing in an Expression at all instead of just a bool? — Kelly Ethridge, Sep 22 '12 at 19:49
@ChaosPandion: It's helpful for me since I don't need to use an if on my view. — Esteban, Sep 22 '12 at 19:57
@KellyEthridge: Because I want to do a DisplayBooleanFor instead of DisplayBoolean. — Esteban, Sep 22 '12 at 20:05
possible duplicate of [Access to Modified Closure (2)](http://stackoverflow.com/questions/304258/access-to-modified-closure-2) — nawfal, Nov 02 '13 at 06:52

score 25 · Accepted Answer · answered Sep 22 '12 at 19:45

25

A block scoped variable should resolve the warning.

@foreach(var item in Model)
{
    var myItem = item;
    <div>@Html.DisplayBooleanFor(modelItem => myItem.BooleanField)</div>
}

answered Sep 22 '12 at 19:45

ChaosPandion

77,506
18
119
157

1

Thank you, it fixed the warning, any idea why this happens? – Esteban Sep 22 '12 at 20:10
10

@Esteban there's more on the JetBrains wiki [here](http://confluence.jetbrains.net/display/ReSharper/Access+to+modified+closure) (which depending on your version of R# may be linked directly from the lightbulb menu as 'Why is ReSharper suggesting this?); see also [this SO question](http://stackoverflow.com/questions/235455/access-to-modified-closure?rq=1) – AakashM Sep 24 '12 at 08:17
2

@Esteban That's the best explication I found so far : http://stackoverflow.com/questions/14907987/access-to-foreach-variable-in-closure – ForceMagic Feb 12 '14 at 15:19

score 2 · Answer 2 · edited Nov 17 '14 at 16:21

2

Another option is to apply JetBrains.Annotations.InstantHandleAttribute attribute to DisplayBooleanFor method.

edited Nov 17 '14 at 16:21

fedorqui

275,237
103
548
598

answered Nov 17 '14 at 16:00

Ivan

21
1

How do I fix: Access to foreach variable in closure resharper warning?

2 Answers2