Adding String to List MVC - html

Question

Im using MVC4 Razor and I just want to ask how to create a List of string and use it in a field seperated by comma? Cause I tried something and it shows an error Cannon implicitly convert type void to object Ill show you my set of codes
declared this on my header:
List<string> elements = new List<string>();
Then I want this List<string> elements to get populated inside a foreach loop
<tbody>
#for (var i = 0; i < Model.Cards.Count; ++i)
{
var counter = i + 1;
<tr>
<td valign="middle">
<p class="small">#counter</p>
</td>
<td valign="middle">
<p class="small">#Model.Cards[i].Number.Substring(0,5)</p>
</td>
#elements.Add(Model.Cards[i].Number.Substring(0,5))
</tr>
}
</tbody>
And use it in a Label
<div> Card Number <p> #String.Join(", ", elements.ToArray()) </p></div>

Answer 1

If you flow #Stephen Muecke, suggestion it's best. But if you flow your process the your code look like:
#{
List<string> elements = new List<string>();
}
<tbody>
#for (var i = 0; i < Model.Cards.Count; ++i)
{
var counter = i + 1;
var cardNumber=Model.Cards[i].Number.Substring(0,5);
elements.Add(cardNumber);
<tr>
<td valign="middle">
<p class="small">#counter</p>
</td>
<td valign="middle">
<p class="small">#cardNumber</p>
</td>
</tr>
}
</tbody>
#{
var str=string.Join(", ", elements.ToArray());
}
<div> Card Number <p> #str </p></div>