如何索引ICollection <T> 就像他们在这个例子中告诉我的那样？

Question

I'm trying list items in my MVC view, following this example: Model Binding to a List . I'm using MVC 5. There example says to do this:

<%@ Page Inherits="ViewPage<IList<Book>>" %>
<% for (int i = 0; i < 3; i++) { %>
    <%: Html.EditorFor(m => m[i]) %>
<% } %>

I'm trying to do this:

for (int i = 0; i < Model.SubmissionTypesSelected.Count(); i++)
{
    Html.EditorFor(m => m.SubmissionTypesSelected[i]);
}

SubmissionTypesSelected is defined like this:

public ICollection<PTSubTypeSelected> SubmissionTypesSelected { get; set; }

I get this message:

Cannot apply indexing to an expression of type 'System.Collections.Generic.ICollection'

Answer 1

The error is kind of self-explanatory; you can't use indexing on an ICollection{T} because it is designed to be able to modify the contents of a collection of elements, not the order of them. Changing it to a IList{T} is a simple answer, as the example you've linked does.

MVC needs to have indexes added in HTML so it can figure out which property value goes with which item in a collection on postback. The EditorFor will do this for you if you pass it an IEnumerable of any kind directly. So you can just do this:

Html.EditorFor(m => m.SubmissionTypesSelected);

It will loop through each item, generate an index for you, and pass the individual item to your editor template.

Answer 2

What happens if you do this:

var typesArray = Model.SubmissionTypesSelected.ToArray();
for (int i = 0; i < typesArray.Length; i++)
{
    Html.EditorFor(m => typesArray[i]);
}

Answer 3

尝试使用CopyTo(Array, Int32) ，然后像通常使用数组一样继续进行迭代。