Setting attribute for HtmlButton in Repeater throws NullReferenceException

Question

I have the code below in the ItemDataBound event for a Repeater control:

HtmlButton btnLike = (HtmlButton)e.Item.FindControl("LikeButton");
var itemLiked = new LikesService().GetByPostIdUserId(pollQ.PostId, new Guid(Membership.GetUser(this.Context.User.Identity.Name).ProviderUserKey.ToString()));
if (itemLiked != null)
    btnLike.Attributes["class"] = "btn btn-primary btn-sm";

I debugged the code but couldn't find why this line throws NullReferenceException:

btnLike.Attributes["class"] = "btn btn-primary btn-sm";

I verified in the debugger that the object itemLiked is not null.

Here is the markup for the HTML button in the Repeater:

<button type="button" id="LikeButton" value='<%#Eval("PollQuestionID") %>' class='<%#GetCSS(Eval("PollQuestionID")) %>'>
    <span class="glyphicon glyphicon-thumbs-up"></span> <%#LikeText(Eval("PollQuestionID")) %>
</button>

@Michael I thought so. But I verified that the name "LikeButton" is the same as what is found in the aspx page. — Kacey Ezerioha, Jul 25 '15 at 18:25
@MichaelLiu Please see the markup in the edited question. Thanks. — Kacey Ezerioha, Jul 25 '15 at 18:36
possible duplicate of [What is a NullReferenceException and how do I fix it?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it) — , Jul 25 '15 at 18:46

score 1 · Accepted Answer · answered Jul 25 '15 at 18:39

1

The FindControl method can only find server controls — those that have the runat="server" attribute. Add this attribute to your <button>:

<button runat="server" type="button" id="LikeButton" ...

answered Jul 25 '15 at 18:39

Michael Liu

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Thanks for your response Michael but the button calls on jQuery ajax event and putting runat="server will cause a postback which I don't want. What do u suggest I do at this point? – Kacey Ezerioha Jul 25 '15 at 18:45
Since you specified `type="button"`, the button won't cause a postback even if it's a server control. – Michael Liu Jul 25 '15 at 18:48
Thanks Michael. I'm so grateful. – Kacey Ezerioha Jul 25 '15 at 18:55

Setting attribute for HtmlButton in Repeater throws NullReferenceException

1 Answers1