C# – Refreshing a Repeater control in an UpdatePanel with ASP.NET

asp.netcrepeaterupdatepanel

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?

Best Answer

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
    }

For MVC v5.1 use Html.EnumDropDownListFor

@Html.EnumDropDownListFor(
    x => x.YourEnumField,
    "Select My Type", 
    new { @class = "form-control" })

For MVC v5 use EnumHelper

@Html.DropDownList("MyType", 
   EnumHelper.GetSelectList(typeof(MyType)) , 
   "Select My Type", 
   new { @class = "form-control" })

For MVC 5 and lower

I rolled Rune's answer into an extension method:

namespace MyApp.Common
{
    public static class MyExtensions{
        public static SelectList ToSelectList<TEnum>(this TEnum enumObj)
            where TEnum : struct, IComparable, IFormattable, IConvertible
        {
            var values = from TEnum e in Enum.GetValues(typeof(TEnum))
                select new { Id = e, Name = e.ToString() };
            return new SelectList(values, "Id", "Name", enumObj);
        }
    }
}

This allows you to write:

ViewData["taskStatus"] = task.Status.ToSelectList();

by using MyApp.Common

.net – ASP.NET Web Site or ASP.NET Web Application

Website:

The Web Site project is compiled on the fly. You end up with a lot more DLL files, which can be a pain. It also gives problems when you have pages or controls in one directory that need to reference pages and controls in another directory since the other directory may not be compiled into the code yet. Another problem can be in publishing.

If Visual Studio isn't told to re-use the same names constantly, it will come up with new names for the DLL files generated by pages all the time. That can lead to having several close copies of DLL files containing the same class name, which will generate plenty of errors. The Web Site project was introduced with Visual Studio 2005, but it has turned out not to be popular.

Web Application:

The Web Application Project was created as an add-in and now exists as part of SP 1 for Visual Studio 2005. The main differences are the Web Application Project was designed to work similarly to the Web projects that shipped with Visual Studio 2003. It will compile the application into a single DLL file at build time. To update the project, it must be recompiled and the DLL file published for changes to occur.

Another nice feature of the Web Application project is it's much easier to exclude files from the project view. In the Web Site project, each file that you exclude is renamed with an excluded keyword in the filename. In the Web Application Project, the project just keeps track of which files to include/exclude from the project view without renaming them, making things much tidier.

Reference

The article ASP.NET 2.0 - Web Site vs Web Application project also gives reasons on why to use one and not the other. Here is an excerpt of it:

You need to migrate large Visual Studio .NET 2003 applications to VS 2005? use the Web Application project.

You want to open and edit any directory as a Web project without creating a project file? use Web Site project.

You need to add pre-build and post-build steps during compilation? use Web Application project.

You need to build a Web application using multiple Web projects? use the Web Application project.

You want to generate one assembly for each page? use the Web Site project.

You prefer dynamic compilation and working on pages without building entire site on each page view? use Web Site project.

You prefer single-page code model to code-behind model? use Web Site project.

Web Application Projects versus Web Site Projects (MSDN) explains the differences between the web site and web application projects. Also, it discusses the configuration to be made in Visual Studio.