Fix IList.Insert example to handle index == Count case

[Copilot]

The IList.Insert example implementation doesn't handle the documented behavior when index == Count. Per the IList documentation: "If index equals the number of items in the IList, then item is appended to the end."

Changes

• C# Insert method: Changed condition from index < Count to index <= Count
• VB.NET Insert method: Changed condition from index < Count to index <= Count

Example

var list = new SimpleList();
list.Add("one");
list.Add("two");

// Before: Insert(2, "three") does nothing (index == Count was rejected)
// After: Insert(2, "three") appends to end as documented
list.Insert(list.Count, "three");

Original prompt

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This section details on the original issue you should resolve

<issue_title>IList example does not meet end-of-list Insert behavior</issue_title>
<issue_description>### Type of issue

Code doesn't work

Description

The example Insert implementation does nothing when index==Count. Expected behavior is to add to the end of the list, according to the IList documentation, under "Remarks:"

If index equals the number of items in the IList, then item is appended to the end.

Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.collections.ilist.insert?view=net-10.0

Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System.Collections/IList.xml

Document Version Independent Id

29468c75-c596-f099-ce36-2fced37f38b0

Platform Id

441396e6-57a0-1e5d-c43d-8fa0c05bcb1a

Article author

@dotnet-bot</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes IList example does not meet end-of-list Insert behavior #12282

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[Copilot]

Pull request overview

This PR updates the IList.Insert example implementations so index == Count is treated as an append, matching the documented IList.Insert behavior.

Changes:

• Update C# SimpleList.Insert to accept index <= Count.
• Update VB.NET SimpleList.Insert to accept index <= Count.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
snippets/csharp/System.Collections/IList/Overview/Program.cs	Allows Insert(Count, value) to append in the C# snippet.
snippets/visualbasic/System.Collections/IList/Overview/Program.vb	Allows Insert(Count, value) to append in the VB snippet (but see noted bug).

Comments suppressed due to low confidence (1)

snippets/visualbasic/System.Collections/IList/Overview/Program.vb:97

• Insert can throw IndexOutOfRangeException when inserting at index 0 (including into an empty list). The shift loop runs down to index, so when i == 0 it evaluates _contents(i - 1).

Adjust the shift loop so it only copies elements when i > index (or stop at index + 1) so i - 1 never becomes -1, and end-of-list inserts still work.

        If _count + 1 <= _contents.Length AndAlso index <= Count AndAlso index >= 0 Then
            _count += 1

            For i As Integer = Count - 1 To index Step -1
                _contents(i) = _contents(i - 1)