Adding a base tag to your ASP code dynamically

Introduction

When using relative paths in your HTML code, it is helpful to set the base tag. But that base may be different for each developer on your team, or on stage, QA, or production. Also, when making your URL optimized for search engines, your URL will map to a non-existing path. The best way to solve this is by adding the <base href="..."/> tag to the page header dynamically.

Using the code

The solution is quite simple. First, create a new class called BaseTag that has the following code:

public class BaseTag : HtmlControl
{
    public BaseTag(HttpRequest request): base("base")
    {
        base.Attributes.Add("href", 
            request.Url.Scheme + "://" + 
            request.Url.Authority + 
            request.ApplicationPath + "/");
    }
}

The key part is Url.Scheme that returns the URL scheme: such as HTTP and HTTPS. Url.Authority returns the host and port address, if one is provided. Next is the application path that is often unique to the location of the web app directory. Put them all together with the right string construct, and you get a nice well formed href for the base tag like:

http://someurl:8080/web/

Next, include the following line in the Page_Load method of your *.aspx.cs file:

protected void Page_Load(object sender, EventArgs e)
{
    this.Header.Controls.AddAt(0, new BaseTag(Request)); 
}

The end result is the <base href="http://someurl:8080/web/"/> tag.

I hope this is helpful to you.