ASP.NET: Setting the Style of an HTML element Programatically

Question

Hi!

I'm generating a menu with a Repeater control bound to an XmlDataSource.

<asp:Repeater ID="myRepeater" runat="server" 
    DataSourceID="myDataSource" 
    onitemdatabound="myRepeater_ItemDataBound" 
    onitemcreated="myRepeater_ItemCreated">
    <HeaderTemplate>
        <ul class="menu_list">
    </HeaderTemplate>
    <ItemTemplate>
        <li id="liMenu" runat="server"><asp:HyperLink ID="hrefMenuItem" runat="server" Text='<%# XPath("@text")%>' NavigateUrl='<%# XPath("@href")%>'></asp:HyperLink></li>
    </ItemTemplate>
    <FooterTemplate>
        </ul>
    </FooterTemplate>
</asp:Repeater>
<asp:XmlDataSource runat="server" ID ="myDataSource" XPath="Menu/Items/*" EnableCaching="False" />

I'd like to be able to set the style of the containing LI based on mouseover events and currently selected menu item. I tried via the HtmlGenericControl, but I receive an error that it's readonly.

protected void myRepeater_ItemDataBound(object sender, RepeaterItemEventArgs e)
        {
            if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
            {
                HyperLink hrefCurrentMenuLink = e.Item.FindControl("hrefMenuItem") as HyperLink;
                HtmlGenericControl l_genericControl = e.Item.FindControl("liMenu") as HtmlGenericControl;

                if ((hrefCurrentMenuLink != null) && (l_genericControl != null))
                {
                    string l_currentPage = GetCurrentWebPage();

                    if (String.Compare(Path.GetFileNameWithoutExtension(hrefCurrentMenuLink.NavigateUrl), l_currentPage, StringComparison.OrdinalIgnoreCase) == 0)
                        l_genericControl.Style = "on-nav";
                    else
                        l_genericControl.Style = "off-nav";

                    l_genericControl.Attributes.Add("onmouseover", "navOn(this)");
                    l_genericControl.Attributes.Add("onmouseout", "navOff(this)");
                }
            }
        }

Is there any way to accomplish this?

Answer 1

The style property is a collection. Do this:

l_genericControl.Style.Add("css-name", "css-value")

Or if you are using CSS classes, then change the CssClass property:

l_genericControl.CssClass = "on-nav";

If you're trying to toggle the CSS class with your javascript, try something like this (untested):

l_genericControl.Attributes.Add("onmouseover", "this.className='on-nav';");
l_genericControl.Attributes.Add("onmouseout", "this.className='off-nav';");

If you want to change the style with your javascript, this might work:

l_genericControl.Attributes.Add("onmouseover", "this.style.color='red'; this.style.backgroundColor='yellow';");
l_genericControl.Attributes.Add("onmouseout", "this.style.color='black'; this.style.backgroundColor='none';");

Answer 2

at the basic level, you could do:

l_genericControl.Attributes["class"] = "on-nav";

Answer 3

The problem is with this part:

l_genericControl.Style = "off-nav";

which you can fix by applying a CssClass instead

// += to prevent overwriting a class you would set in the markup
l_genericControl.CssClass += "off-nav";