Web Forms :: Redirect To Error Page When Entered Code Be Wrong

I have button and textbox in Trade.aspx page that users enter Number in TB and according to that Number it go to other page 

protected void Trade_Click(object sender, ImageClickEventArgs e) {
string data = Server.UrlEncode(txtNumeric.Text);
SqlCommand _cmd = new SqlCommand("traidname", _cn);
_cmd.CommandType = CommandType.StoredProcedure;
_cmd.Parameters.Add("@BehCode", data);
_cn.Open();
string tName = _cmd.ExecuteScalar().ToString();
_cn.Close();
Response.Redirect(tName + "?BehCode=" + Server.UrlEncode(txtNumeric.Text));
}

Now I want if users enter wrong number in TB that doesn't exist in database it redirect to Error.aspx page