asp.net下拉列表SelectedIndexChanged不起作用

Question

我有两个功能：

1. 创建下拉列表
2. 它的事件处理程序（试图重定向......只是为了知道它正在工作）。

但它不起作用.. 请帮助:(

创建下拉列表：

DropDownList createUsersDropDownList(ShiftClass shift, string selectedDate,int dayNumber)//creating the drop down list of users of shift
{
    DropDownList output=new DropDownList();
    output.Items.Add(new ListItem("","0"));
    List<UserClass> listOfUsers = new List<UserClass>();
    //arrange.watchersRoles = list of roles can watch
    DateTime theDate = DateTime.Parse(selectedDate);
    DBConnect dbConn = new DBConnect();
    using (dbConn.conn)
    {
        SqlCommand sqlGetUserDetails;
        SqlDataReader rsGetUserDetails;
        foreach (int allowedRole in arrange.watchersRoles)//for every role, create userclass
        {
            sqlGetUserDetails= new SqlCommand("select ID from dbo.Users where roleID=" + allowedRole, dbConn.conn);//calling the allowed users with id
            rsGetUserDetails = sqlGetUserDetails.ExecuteReader();
            if (rsGetUserDetails.HasRows)
                while(rsGetUserDetails.Read())  //get the details from db
                    listOfUsers.Add(new UserClass((int)rsGetUserDetails["ID"]));//adding the user to the list
            rsGetUserDetails.Close();
        }//end foreach role
        dbConn.conn.Close();
    }//end using conn

    ListItem userToAdd;

    foreach (UserClass allowedUser in listOfUsers)//foreach user, add him to the drop down list
    { 

        userToAdd=new ListItem();
        UserClass currentUserInShift = shift.userInShift(shift.shiftID, dateToSql(theDate.AddDays(0).Date));
        if(currentUserInShift!= null )//there is user in this shift
            if (allowedUser.userData.id == currentUserInShift.userData.id)//user is equal ==>  selected
                userToAdd.Selected = true;
        userToAdd.Value=allowedUser.userData.id.ToString();
        userToAdd.Text=allowedUser.userData.firstName + " " + allowedUser.userData.lastName;
        output.Items.Add(userToAdd);

    }

    output.ID = theDate.AddDays(0).Date + "_" + shift.shiftID.ToString();
    output.SelectedIndexChanged += new EventHandler(updateUserInShift);
    output.EnableViewState = true;
    output.AutoPostBack = true;

    return output;
}//end createDropDownList

事件处理程序：

protected void updateUserInShift(object sender, EventArgs e)
{
    string originalShift;
    string date;
    int userID;

    DropDownList selectedList = (DropDownList)sender;

    originalShift = selectedList.ID;
    Page.Response.Redirect("http://www.google.com", true);
}

**但没有任何反应......有一个回复但没有事件处理程序.. **