Accessing app setting from aspx and add concatenated text

Question

I've got a project where I'm tasked with changing hard-coded domain references from one domain to another in a group of legacy C#/VB web projects. I want to parameterize the domains as much as possible instead of just replacing with a different hard-coded value. The problem is that there are over 800 of these references in about 30 different solutions, so creating variables in each code-behind to bind to would take forever.

I have added the new domains to the appSettings section of the web.config file, and this works:

<asp:HyperLink Text="Link" NavigateUrl="<%$appSettings:DomainX %>" runat="server" />

But I need to be able to do something like this:

<asp:HyperLink Text="Link" NavigateUrl="<%$appSettings:DomainX %>/newPage.aspx" runat="server" />

But when I add the "/newPage.aspx" the page doesn't compile anymore. I don't really care if this is done with an asp:HyperLink tag or just a tag.

Any ideas on how I can accomplish this?

Thanks.

Answer 1

I think you have two options. The easiest is to just use a plain old anchor tag, if you're not doing anything with the HyperLink server side:

<a href="<%= string.Concat(ConfigurationManager.AppSettings["DomainX"], "/newPage.aspx") %>">Link</a>

Alternatively, you could set the NavigateUrl in the Page_Load, since <%= will not work properly within the HyperLink server tag:

protected void Page_Load(object sender, EventArgs e)
{
    if(!Page.IsPostBack)
        link1.NavigateUrl = string.Concat("http://", 
                  ConfigurationManager.AppSettings["DomainX"], "/newPage.aspx");
}

You could also see if you can make a custom binding, something like $myBinding:DomainX, but I don't know if that's possible off the top of my head (I would assume it is though).

EDIT
That $appSettings:DomainX code is called an ASP.NET Expression, and can you can create custom expressions. This post from Phil Haack covers how to set them up, in case you are interested.