Refreshing a Repeater control in an UpdatePanel with ASP.NET

Question

I'm trying to code a page where you can post a comment without reloading the whole page. The comments are displayed using a Repeater control. The template looks like this:

    <asp:UpdatePanel runat="server" ID="commentsUpdatePanel" UpdateMode="Conditional">
        <ContentTemplate>
        <!-- Comments block -->
        <div class="wrapper bloc content">
            <h3><img src="img/comments.png" alt="Comments" />&nbsp;Comments</h3>                                     
            <p><asp:Label ID="viewImageNoComments" runat="server" /></p>
            <asp:Repeater ID="viewImageCommentsRepeater" runat="server">
                <HeaderTemplate>
                    <div class="float_box marge wrapper comments">
                </HeaderTemplate>
                <ItemTemplate>
                    <div class="grid_25">
                        <span class="user"><%#Eval("username")%></span><br />
                        <span style="font-size:x-small; color:#666"><%#Eval("datetime") %></span>
                    </div>
                    <div class="grid_75">
                        <p align="justify"><%#Eval("com_text") %></p>
                    </div>
                </ItemTemplate>
                <FooterTemplate>
                    </div>
                </FooterTemplate>
            </asp:Repeater>
        </div>
        <!-- Post comment block -->
        <div class="wrapper bloc content">
            <h3><a id="post_comment" name="post_comment"><img src="img/comment_edit.png" alt="Comments" /></a>&nbsp;Post 
                a comment</h3>
            <p class="description">Please be polite.</p>
            <p>
                <asp:Label ID="postCommentFeedback" runat="server" />
            </p>
            <table border="0">
                <tr>
                    <td valign="top">
                    <asp:TextBox id="postCommentContent" runat="server" TextMode="MultiLine" 
                    MaxLength="600" Columns="50" Rows="15" Width="400px" />
                    </td>
                    <td valign="top">
                    <span style="font-size:x-small">BBCode is enabled. Usage :<br />
                    <b>bold</b> : [b]bold[/b]<br />
                    <i>italic</i> : [i]italic[/i]<br />
                    <span class="style1">underline</span> : [u]underline[/u]<br />
                    Link : [url=http://...]Link name[/url]<br />
                    Quote : [quote=username]blah blah blah[/quote]</span>
                    </td>
                </tr>
                <tr>
                    <td colspan="2">
                    <asp:Button ID="postCommentButton" runat="server" Text="Submit" 
                    onclick="postCommentButton_Click" />    
                    </td>
                </tr>
            </table>
            </div>
        </ContentTemplate>
    </asp:UpdatePanel>

The postCommentButton_Click() function works just fine - clicking "Submit" will make the post. However, I need to completely reload the page in order to see new comments - the post the user just made will not show until then. I Databind the Repeater in Page_Load() after a (!isPostBack) check.

The postCommentButton_Click() function looks like this:

protected void postCommentButton_Click(object sender, EventArgs e)
{
        // We check if user is authenticated
        if (User.Identity.IsAuthenticated)
        {
            // Attempt to run query
            if (Wb.Posts.DoPost(postCommentContent.Text, Request.QueryString["imageid"].ToString(), User.Identity.Name, Request.UserHostAddress))
            {
                postCommentFeedback.Text = "Your post was sucessful.";
                postCommentContent.Text = "";

            }
            else
            {
                postCommentFeedback.Text = "There was a problem with your post.<br />";
            }

        }
        // CAPTCHA handling if user is not authenticated
        else
        {
            // CAPTCHA
        }
}

In my case, we do see postCommentFeedback.Text refreshed, but, again, not the content of the repeater which should have one more post.

What is it I'm missing?

Answer 1

You should DataBind in the Page_Load within a !IsPostBack as you are. You should ALSO databind in your Click event.

    protected void Page_Load(object sender, EventArgs e)
    {
        if(!IsPostBack)
        {
            this.DataBind();
        }
    }
    protected void MyButton_Click(object sender, EventArgs e)
    {
        //Code to do stuff here...

        //Re DataBind
        this.DataBind();
    }
    public override void DataBind()
    {
        //Databinding logic here
    }

Answer 2

Instead of making your datasource a MySqlDataReader, have your reader populate a BindingList or something like that. Keep that in session and do your databind every non-postback and click. When your user posts, you can either add it to the list and wait for something to tell it to save that, but it makes more sense in the context of posting comments to save their post to your db and redo your datapull and stomp over your BindingList and re-Databind.

Also, personal peeve: I dislike <%#Eval....%>. Code in your page is usually a bad sign. Try using the Repeater.ItemDataBound Event http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.repeater.itemdatabound.aspx

Answer 3

It sounds to me like the quick fix is to bind on page load regardless of postback. Alternatively, you could rebind from within postCommentButton_Click.