ID Being Rendered As Null In A Typed Razor View

问题

This is really weird, for some reason the Id of the ViewModel is being rendered as null inside the view. I debugged the application and checked that the view model is actually being mapped correctly (using AutoMapper) and everything is fine. But when I do @Model.Id, it is rendering as zero, and when I alert the value using jQuery I get "null". So what's going on?

            <div id="commentBox">
                @using (Html.BeginForm("Comment", "Item", new { itemId = Model.Id  } ))
                {
                    <span class="greenText">answer</span>
                    <span id="hiddenForId">@this.Hidden(x => x.Id).Id("idPlaceHolder")</span>
                    <span id="commentInputBox">@this.TextBox(x=>x.CommentText).Id("commentField")</span>
                    <span id="commentButton">@this.SubmitButton("").Id("commentSubmit").Class("okButton")</span>
                }
            </div>

        <div style="clear:both"></div>
    </div> 
</div>

<script type="text/javascript">
    $(function () {
        alert($("idPlaceHolder").html());
        $("#commentSubmit").click(function () {
            var dataObj = { 'commentText': $("#commentField").val(), 'itemId': $("idPlaceHolder").html() }
            $.ajax({
                url: '/Item/Comment',
                data: dataObj,
                type: 'POST',
                success: function (result) {
                    if (result.redirectTo != null && result.redirectTo != '') {
                        window.location.href = result.redirectTo;
                    } else {
                        alert(result.error);
                    }
                }
            });
            return false;
        });
    });
</script>

P.S: on a side note, how do you tell the form that it doesn't need to post and that it has been taken care of? I just cannot remember it... It's definitely something other than return false;

回答1:

Partial answer: if you return false on a form's onsubmit event it will prevent the form from submitting.

回答2:

Right before you display the view - the model does have a value for ID, correct? In that case is this on a post? If so - if there are issues and you redisplay the form without a redirect MVC assumes an error it will use what was in the posted values to write back out- assuming you are creating a new record and the comment id was originally null. if this isnt during post/redisplay then this answer doesn't apply.

回答3:

Ok I've finally figured out what was going wrong:

$(function () {
    alert($("#idPlaceHolder").val());
    $("#commentSubmit").click(function () {
        var dataObj = { 'commentText': $("#commentField").val(), 'itemId': $("#idPlaceHolder").val() }

I was using $("idPlaceHolder").html() instead of $("#idPlaceHolder").val()... syntax error!

来源：https://stackoverflow.com/questions/5720605/id-being-rendered-as-null-in-a-typed-razor-view