Question

I’m building a very simple ASP.NET user control to display messages with the help of jQuery UI styling.

For this, I built a separate web project, which is referenced by the site project.
I referenced it in web.config, like this:

<pages>
  <controls>
    <add tagPrefix="uc" namespace="Website.Main.UserControls" assembly="Website.Main.UserControls" />
  </controls>
</pages>

Then in a test page, I instanced it like this:

<uc:StatusMessage ID="Test" runat="server" Type="Help" Text="testing.." />

Here’s the code for the control

using System;

namespace Website.Main.UserControls
{
    public partial class StatusMessage : System.Web.UI.UserControl
    {
        public enum MessageType
        {
            Error,
            Notice,
            Help,
            Info,
            Success
        }

        public string Text
        {
            get { return Message.Text; }
            set
            {
                Message.Text = value;
            }
        }

        private MessageType _type;
        public MessageType Type
        {
            get { return _type; }
            set
            {
                _type = value;

                if (_type == MessageType.Error)
                {
                    MessageContainer.Attributes["class"] = "ui-icon ui-icon-alert";
                    MessageIcon.Attributes["class"] = "ui-state-error ui-corner-all";
                }
                else
                {
                    MessageIcon.Attributes["class"] = "ui-state-highlight ui-corner-all";

                    if (_type == MessageType.Notice)
                    {
                        MessageContainer.Attributes["class"] = "ui-icon ui-icon-notice";
                    }
                    else if (_type == MessageType.Help)
                    {
                        MessageContainer.Attributes["class"] = "ui-icon ui-icon-help";
                    }
                    else if (_type == MessageType.Info)
                    {
                        MessageContainer.Attributes["class"] = "ui-icon ui-icon-info";
                    }
                    else if (_type == MessageType.Success)
                    {
                        MessageContainer.Attributes["class"] = "ui-icon ui-icon-check";
                    }
                }
            }
        }

        protected void Page_Load(object sender, EventArgs e)
        {

        }

        public void SetText(string text, MessageType type = MessageType.Info)
        {
            Text = text;
            Type = type;

            StatusMessagePanel.Update();
        }
    }
}

And the markup

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="StatusMessage.ascx.cs" Inherits="Website.Main.UserControls.StatusMessage" %>

<asp:UpdatePanel ID="StatusMessagePanel" runat="server" UpdateMode="Conditional">
    <ContentTemplate>
        <div class="ui-widget">
            <div style="margin-top: 20px; padding-left: 7px; padding-top: 7px;" class="ui-state-highlight ui-corner-all" id="MessageContainer" runat="server"> 
                <p>
                    <span style="float: left; margin-top: 4px; margin-right: .3em;" class="ui-icon ui-icon-info" id="MessageIcon" runat="server"></span>
                    <asp:Label ID="Message" runat="server"></asp:Label>
                </p>
            </div>
        </div>
    </ContentTemplate>
</asp:UpdatePanel>

The problem is, whenever I get to the codebehind for this control, that is, right when the page renders and takes the attributes, all of the uc members are null. That is: Message, MessageContainer, MessageIcon and StatusMessagePanel are all null.

I have no clue what’s causing this behavior, I tried removing the update panel but nothing changes.

Answer 1

Using web.config file you can register only server web controls. But for user controls you must add register tag onto each page where those controls are used. Like this: <%@ Register TagPrefix="uc" TagName="StatusMessage " Src="~/UserControls/StatusMessage .ascx" %>