C# - Apply Skin To A Control Created Programmatically?

Say I am creating a Textbox in the codebehind of a page like this:

protected override void OnInit(EventArgs e)
{
base.OnInit(e);
TextBox test = new TextBox();
test.SkinkId = "MySkin";
placeHolder.Controls.Add(test);
}

and in my skin file I have this:

<asp:TextBox
runat="server"
SkinId = "MySkin"
Width="400"
/>

Why is the skin not beeing applied to the control. If i declare the control in my aspx page it works ok, but if I try to do it programatically it does not work...