您可以通过为具有不同 id 的不同选择生成选项并为Url属性呈现隐藏字段来实现。尝试以下:
<select id="url-list">
      @foreach(var item in Model.individualPages)
       {
           <option value="@Model.Url">
              @Model.Url
           </option>
       }
        <option > custom... </option>
</select>
<input type="text" id="custom-url"/>
@Html.HiddenFor(e=>e.Url)
<script>
   $(document).ready(function(){
        $("select#url-list").change(function(){
              var selectedItem =$("option:selected",$(this)),
                    selectedValue = selectedItem.val();
              $("#url").val(selectedValue);
        });
        $("form").submit(function(){
              var selectedItem = $("option:selected",$("select#url-list")),
                    selectedIndex = selectedItem.index(),
                      itemCount = $("option",$("select#url-list")).length;
                if (selectedIndex == itemCount -1)
                     $("#url").val($("#custom-url").val());
        });
   });
</script>