Trying to set value for ViewBag
@foreach (var invoice in Model.Invoices)
{
    @{ ViewBag.InvoiceTotal = (invoice.Product.Price * invoice.Quantity).ToString("c"); }

    <tr>
        <td>
            @Html.DisplayFor(modelItem => invoice.InvoiceDate)
        </td>
        <td>
            @Html.DisplayFor(modelItem => invoice.Company.Name)
        </td>
        <td>
            @Html.DisplayFor(modelItem => invoice.Product.Name)
        </td>
        <td>
            @Html.DisplayFor(modelItem => invoice.Quantity)
        </td>
        <td>
            @Html.DisplayFor(modelItem => invoice.Product.Price)
        </td>
        <td>
            @ViewBag.InvoiceTotal
        </td>
        <td>
            @Html.ActionLink("Edit", "Edit", new { id = invoice.InvoiceId }) |
            @Html.ActionLink("Details", "Details", new { id = invoice.InvoiceId }) |
            @Html.ActionLink("Delete", "Delete", new { id = invoice.InvoiceId })
        </td>
    </tr>
}

@foreach (var invoice in Model.Invoices)
 {
  {
  ViewBag.InvoiceTotal = (invoice.Product.Price * invoice.Quantity).ToString("c");
  }
}

@foreach (var invoice in Model.Invoices)
            {
                 ViewBag.InvoiceTotal = (invoice.Product.Price * invoice.Quantity).ToString("c");

                <tr>
                    <td>
                        @Html.DisplayFor(modelItem => invoice.InvoiceDate)
                    </td>
                    <td>
                        @Html.DisplayFor(modelItem => invoice.Company.Name)
                    </td>
                    <td>
                        @Html.DisplayFor(modelItem => invoice.Product.Name)
                    </td>
                    <td>
                        @Html.DisplayFor(modelItem => invoice.Quantity)
                    </td>
                    <td>
                        @Html.DisplayFor(modelItem => invoice.Product.Price)
                    </td>
                    <td>
                        @ViewBag.InvoiceTotal
                    </td>
                    <td>
                        @Html.ActionLink("Edit", "Edit", new { id = invoice.InvoiceId }) |
                        @Html.ActionLink("Details", "Details", new { id = invoice.InvoiceId }) |
                        @Html.ActionLink("Delete", "Delete", new { id = invoice.InvoiceId })
                    </td>
                </tr>
            }