"The SelectCommand property has not been initialized before calling 'Fill'.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        SqlConnection cn = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=C:\\Users\\MANTHAN\\Documents\\Visual Studio 2010\\WebSites\\sample\\App_Data\\Database.mdf;Integrated Security=True;User Instance=True");
        cn.Open();
        SqlCommand cmd = new SqlCommand("SELECT * FROM stu1", cn);
        SqlDataAdapter adp = new SqlDataAdapter();
      
       
        DataSet ds = new DataSet();
        

        adp.Fill(ds);
        cn.Close();
        
        GridView1.DataSource = ds.Tables[0];


    }
}