I am using an IEnumerable extension to loop through a collection and also get its index:
@Model.ForEach((card, i) => {
@<li class="c@(i)">@card.Text</li>;
})
The ForEach extension is the following:
public static void ForEach<T>(this IEnumerable<T> source, Action<T, Int32> action) {
Int32 i = 0;
foreach (T item in source) {
action(item, i);
i++;
}
} // ForEach
But when I try to compile it I get the following error message:
Argument 1: cannot convert from 'void' to
'System.Web.WebPages.HelperResult'
How can I solve this? Do I need a new extension?
Your problem is that Razor expects your ForEach method to return a value, such as MvcHtmlString.
Also, you cannot simply expect Razor to translate the body of your foreach clause to work with your Action delegate. There is a way to get this to work, but it's not as pretty. I'd suggest using the @for(...) clause as James suggested if you want to use the standard razor syntax.
However, here's an implementation that does work:
public static MvcHtmlString ForEach<T>(this IEnumerable<T> source, Func<T, Int32, string> selector)
{
return new MvcHtmlString(String.Join("\n", source.Select(selector)));
}
Usage:
@Model.ForEach((card, i) =>
{
return "<li class=c" + i + ">" + card.Text + "</li>";
})
This works, but it feels hackish:
public static HelperResult ForEach<T>(this IEnumerable<T> source, Func<T, int, Func<TextWriter, HelperResult>> action) {
return new HelperResult((writer) => {
int i = 0;
foreach (T item in source) {
action(item, i)(writer).WriteTo(writer);
i++;
}
});
}
@Model.ForEach((card, i) =>
@<li class="c@(i)">@card.Text</li>
)
