wirdest eror in c# page :  the c# code:

    using (c)
          {
                c.Open();
            using (SqlCommand command = new SqlCommand("DELETE FROM [User]  WHERE Username like @username", c))
            {
                command.Parameters.AddWithValue("@username", txtuser.Text);
                command.ExecuteNonQuery();
            }
                c.Close();
        }
            Response.Redirect("Manger Control.aspx", true);
        }
the eror:

> An exception of type 'System.InvalidOperationException' occurred in
> System.Data.dll but was not handled in user code
> 
> Additional information: The connection was not closed. The
> connection's current state is open.