how to add css class to html generic control div?

I created a div tag like this:

System.Web.UI.HtmlControls.HtmlGenericControl dynDiv = 
    new System.Web.UI.HtmlControls.HtmlGenericControl("DIV");

I added style to the div tag like this:

dynDiv.Style.Add(HtmlTextWriterStyle.BorderStyle, "1px solid #DBE0E4");
dynDiv.Style.Add(HtmlTextWriterStyle.Height, "auto");
dynDiv.Style.Add(HtmlTextWriterStyle.MarginTop, "5px");
dynDiv.Style.Add(HtmlTextWriterStyle.PaddingBottom, "5px");
dynDiv.Style.Add(HtmlTextWriterStyle.Width, "682px");

But I need to control the style of the div tag through an external css file located at folder ~/css/maincss.css.

How can I apply the css in that file to this div?

Solution 1:

dynDiv.Attributes["class"] = "myCssClass";

Solution 2:

To add a class to a div that is generated via the HtmlGenericControl way you can use:

div1.Attributes.Add("class", "classname"); 

If you are using the Panel option, it would be:

panel1.CssClass = "classname";

Solution 3:

if you want to add a class to an existing list of classes for an element:

element.Attributes.Add("class", element.Attributes["class"] + " " + sType);