Click event can't see radiobutton control

I have a radio button list on my aspx page. In my codebehind page, I have a button click event. But when I run the page I get this error: "The name 'RadioButtonList1' does not exist in the current context"

protected void GameSearchButton_Click(object sender, EventArgs e)
{
if (RadioButtonList1.SelectedValue == "games") //THROWS ERROR
{...
}

}

What am I doing wrong? ...