Cannot apply index with [ ] to an expression of type icollection MVC view ASP.NET core 2.1

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cannot apply index with [ ] to an expression of type Icollection mvc view asp.net core 2.1

public class SalesHeader
    {
        public SalesHeader()
        {

        }
        public int SalesYear { get; set; }
        public int BranchCode { get; set; }
        public ICollection<SalesFooter> SalesFooters { get; set; }
    }

What I have tried:

@for (var i = 0; i < Model.SalesFooters.Count; ++i)
                   {
                       <tr>
                           <td>
                               @Html.EditorFor(f => f.SalesFooters[i].ItemCode)
                           </td>
                           <td>
                               @Html.EditorFor(f => f.SalesFooters[i].Quantity)
                           </td>
                           <td>
                               @Html.EditorFor(f => f.SalesFooters[i].UnitPrice)
                           </td>
                       </tr>
                   }

it show my in for loop above compile error

cannot apply index with [ ] to an expression of type Icollection mvc view asp.net core 2.1

How to solve this error please ?

Posted 14-Feb-19 1:58am

ahmed_sa

Updated 14-Feb-19 2:55am

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OriginalGriff · Answer 1 · 2019-02-14T02:35:00

ICollection is the base interface for all Collection classes in .NET: ICollection Interface (System.Collections) | Microsoft Docs[^]
Which means that IList is derived from ICollection, not the other way around. IList supports indexing, but ICollection does not.

An object that implements IList can be stored in an ICollection variable, but you cannot use IList methods (or indexers) on it without casting it to a IList (which may fail, because not every ICollection object is an IList).

Dave Kreskowiak · Answer 2 · 2019-02-14T02:55:00

The ICollection interface doesn't have a [] indexer defined. You cannot use it like an array.

It does, however, support enumeration. In your case, you can just swap out the for loop with foreach and use the enumerator instead:

C#

@foreach (var footer in Model.SalesFooters)
{
    <tr>
        <td>
            @Html.EditorFor(f => footer.ItemCode)
        </td>
        <td>
            @Html.EditorFor(f => footer.Quantity)
        </td>
        <td>
            @Html.EditorFor(f => footer.UnitPrice)
        </td>
    </tr>
}

Cannot apply index with [ ] to an expression of type icollection MVC view ASP.NET core 2.1

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