ASP.NET GridView Image Command Button Problem (Multiple PostBacks)

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.ComponentModel;

namespace WebApplication
{
    [DataObject(true)]
    public class DataAdapter
    {
        /// <summary>
        /// This method is called by the ObjectDataSource when the GridView is bound.
        /// Therefore we return some dummy data sorted by the sort expression.
        /// </summary>
        /// <param name="sort">how the data should be sorted.</param>
        /// <returns>Some data</returns>
        [DataObjectMethod(DataObjectMethodType.Select, true)]
        public DataDataSet GetData()
        {
            DataDataSet data = new DataDataSet();

            data.Data.AddDataRow("hello", "asp.net", "world");
            data.Data.AddDataRow("have", "fun", "!");

            data.AcceptChanges();
            return data;
        }
    }
}