Problems with a nested datalist

Question

I have a nested DataList structure DataList2 inside DataList1 where I have two Buttons inside DataList2 that perform certain commands.

I want to call a procedure that takes as input the datakeyfield of DataList1 and datakeyfield of DataList2. However there is a problem with reading the datakeyfield of DataList2. Here is my code:

.aspx.cs code

protected void DataList2_ItemCommand(object source, DataListCommandEventArgs e)
{
    if ((e.CommandName == "accept") && (e.CommandArgument != null))
    {
        string connStr = ConfigurationManager.ConnectionStrings["MyDbConn"].ToString();
        SqlConnection conn = new SqlConnection(connStr);
        int team_ID = (int)DataList1.DataKeys[e.Item.ItemIndex];
        SqlCommand cmd = new SqlCommand("accept_member", conn);
        string member = (string)DataList2.DataKeys[e.Item.ItemIndex];
        cmd.CommandType = CommandType.StoredProcedure;
        string email = Session["email"].ToString();
        int course_ID = Convert.ToInt32(Request.QueryString["courseID"]);
        cmd.Parameters.Add(new SqlParameter("@course_ID", course_ID));
        cmd.Parameters.Add(new SqlParameter("@team_ID", team_ID));
        cmd.Parameters.Add(new SqlParameter("@myemail", email));
        cmd.Parameters.Add(new SqlParameter("@member", member));
        cmd.Parameters.Add(new SqlParameter("@respond", 1));
        SqlParameter count = cmd.Parameters.Add("@count", SqlDbType.Int);
        count.Direction = ParameterDirection.Output;

        conn.Open();
        cmd.ExecuteNonQuery();

        if (@count.Value.ToString().Equals("1"))
        {
            Response.Write(@member + " " + "joined your team");

        }
        else
        {
            Response.Write("team is full or not found");
        }
    }
    else if ((e.CommandName == "reject") && (e.CommandArgument != null))
    {
        int team_ID = (int)DataList1.DataKeys[e.Item.ItemIndex];
        string connStr = ConfigurationManager.ConnectionStrings["MyDbConn"].ToString();
        SqlConnection conn = new SqlConnection(connStr);
        string member = (string)DataList2.DataKeys[e.Item.ItemIndex];
        SqlCommand cmd = new SqlCommand("accept_member", conn);
        cmd.CommandType = CommandType.StoredProcedure;
        string email = Session["email"].ToString();
        int course_ID = Convert.ToInt32(Request.QueryString["courseID"]);
        cmd.Parameters.Add(new SqlParameter("@course_ID", course_ID));
        cmd.Parameters.Add(new SqlParameter("@team_ID", team_ID));
        cmd.Parameters.Add(new SqlParameter("@myemail", email));
        cmd.Parameters.Add(new SqlParameter("@member", member));
        cmd.Parameters.Add(new SqlParameter("@respond", "0"));
        SqlParameter count = cmd.Parameters.Add("@count", SqlDbType.Int);
        count.Direction = ParameterDirection.Output;

        conn.Open();
        cmd.ExecuteNonQuery();

        if (@count.Value.ToString().Equals("1"))
        {
            Response.Write(@member + " " + "has been rejected");
        }
        else
        {
            Response.Write("team is full or not found");
        }
    }

    DataList2.DataBind();
}

Error

The name "DataList2" does not exist in the current context

Answer 1

Assuming that your data produces more than one row in DataList1, there is more than one DataList2. ASP.NET therefore doesn't make DataList2 a member of your page (codebehind) class.

Fortunately, in this instance sender (which you called source, same thing) should be the DataList2 that you want. Try casting it to DataList and see what happens.

Answer 2

You are making a couple of mistakes. First DataList2 is not directly accessible (as you have noticed). And second you are using the same ItemIndex for both the parent and child DataList. But since they are nested they do not have the same values but need to be accesses by a different array index.

protected void DataList2_ItemCommand(object source, DataListCommandEventArgs e)
{
    //cast the source back to a the datalist
    DataList datalist2 = source as DataList;

    //get the value from the nested datalist
    string childValue = (string)datalist2.DataKeys[e.Item.ItemIndex];

    //get the parent object of datalist2
    DataListItem dli = datalist2.NamingContainer as DataListItem;

    //get the value from the parent datalist using the itemindex of the parent, not the child
    int parentValue = (int)DataList1.DataKeys[dli.ItemIndex];

    //show results
    Label1.Text = parentValue + " - " + childValue;

    //rebind datalist2
    datalist2.DataBind();
}