listbox data binding

I try to bind data to my listbox but in listbox I see "System.Data.Common.DbDataReader" where am I doing wrong?

You can see my code below

......

......

string ins="select CategoryName from Category;";

SqlConnection con=new SqlConnection(connstr);

SqlCommand com=new SqlCommand(ins,con);

try

{

con.Open();

SqlDataReader dr=com.ExecuteReader();

kategori.DataSource=dr;

kategori.DataBind();

}

......

......

For ListBox and DropDownList you need to set the control's DataTextField and DataValueField as well as the DataSource before calling DataBind().