How to find HtmlAnchor ID from the web page in C#? Error message: Object reference not set to an instance of an object.

I tried to find the ID of the HtmlAnchor web control through FindControl. But the error seems to say that HtmlAnchor web control instance is null.

The error message:

Object reference not set to an instance of an object.

<a id="hypTest" runat="server" href="#"><img src="/_layouts/15/images/picture.PNG" alt="" /></a>

protected void Page_Load(object sender, EventArgs e)
{
    HtmlAnchor aURL = new HtmlAnchor();
    aURL = (HtmlAnchor)this.Page.FindControl("hypTest");
    aURL.HRef = ''http://www.example.com/'';
}