Find ERROR in this ASP.net BINDING Method.?

[Soul Pure]

protected void Page_Load(object sender, EventArgs e)
{
con1 = ConfigurationSettings.AppSettings["ConnectionString"];

}
public void bind()
{
dset = new DataSet();
SqlConnection con = new SqlConnection(con1);
con.Open();
adp = new SqlDataAdapter("select * from twbs2", con );
adp.Fill(dset, "twbs2");
GridView1.DataSource = dset.Tables["twbs2"];
GridView1.DataBind();
con.Close();
}

When i execute an exception occur:
Both DataSource and DataSourceID are defined on 'GridView1'. Remove one definition.