gridview最本寫法
string ConnectString = @"Data Source=LAPTOP-9BATG3PT\MSSQLSERVER2015;Initial Catalog=NORTHWND;
Integrated Security=True";
using (SqlConnection conn = new SqlConnection(ConnectString))
{
SqlCommand cmd = new SqlCommand("SELECT * FROM Employees");
SqlDataReader dr = cmd.ExecuteReader();
GridView1.DataSource = dr;
GridView1.DataBind();
}