Question

I have a page where users can select different documents files in a datalist control. The documents are categorized based on categories using the on pre-render event handler. Documents are selected based on Checkbox controls (not Checkboxlist). So far so good. What I want to happen next is to put a ‘Select All’ checkbox beside each Category’s name which should select only checkboxes under that category. Here is the datalist control:

<asp:DataList ID="DataList1" runat="server" RepeatDirection="Vertical" OnPreRender="DataList1_PreRender" DataKeyField="docid" EnableViewState="false">
<ItemTemplate>
    <table cellpadding="0" cellspacing="0" id="tbl_data">
        <tr>
            <td>
                <asp:Label ID="lblHeader" runat="server" Font-Bold="True" Font-Underline="True"></asp:Label>
             <asp:Label runat="server" id="lbl_cb_all" visible="false">Select All <input runat="server" id="cb_selectall" type="checkbox" value='<%# Eval("catid") %>' /> </asp:Label>
            </td>
        </tr>

        <tr runat="server" id="tr_data">
            <td>
                <asp:Label ID="lbl_categoryname" runat="server" Text='<%# Eval("categoryname") %>' Visible="false" /> <!-- Hide this; only used in Code Behind -->
                 <input runat="server" id="cb_docid" type="checkbox" value='<%# Eval("docid") %>' />
                  <asp:Hyperlink ID="hpl_docfileencr" Text='<%# Eval("docfileencr") %>' NavigateUrl='<%# "~/PDFEncr/" + DataBinder.Eval(Container.DataItem, "docfileencr") %>' Target="_blank"  runat="server" />
                <br />
            </td>
        </tr>
    </table>
</ItemTemplate>

and here is the OnPreRender code:

protected void DataList1_PreRender(object sender, EventArgs e)
{
    string strTempLabelCategory = "";
    foreach (DataListItem item in DataList1.Items)
    {



        Label lbl_categoryname = item.FindControl("lbl_categoryname") as Label;


        if (strTempLabelCategory.ToUpper() != lbl_categoryname.Text.ToString().ToUpper())
        {
            strTempLabelCategory = lbl_categoryname.Text.ToString().ToUpper();
            Label lblHeader = item.FindControl("lblHeader") as Label;
            lblHeader.Text = strTempLabelCategory.ToUpper();

            Label lbltempdiv = item.FindControl("lbl_cb_all") as Label;
            lbltempdiv.Visible = true;
        }
    }
}

I have looked for something which can work within my code but no luck. And I am too invested in this code to now try Checkboxlist control (not sure if that would help anyway).
Any ideas? I thought I could use: http://www.dotnetcurry.com/ShowArticle.aspx?ID=77 code but not sure how I can make that work? If I can somehow make the select all checkbox tie to a tag and then look for all tag then may be the link’s code would help.
Thanks!

Answer 1

1. Use HiddenFields to store CatID and DocID
2. Use ASP.NET CheckBoxes instead of HTML-Inputs for both
3. Handle the Check-All Checkbox’ CheckedChanged event:

---

protected void CheckAllChanged(Object sender, EventArgs e)
{
    CheckBox checkAll = (CheckBox)sender;
    DataListItem item = (DataListItem)checkAll.NamingContainer;
    HiddenField HiddenCatID = (HiddenField)item.FindControl("HiddenCatID");
    var catCheckBoxes = DataList1.Items.Cast<DataListItem>()
        .Where(li => ((HiddenField)li.FindControl("HiddenCatID")).Value == HiddenCatID.Value)
        .Select(li => li.FindControl("cb_docid"));
    foreach (CheckBox docCheckBox in catCheckBoxes)
    {
        docCheckBox.Checked = checkAll.Checked;
    }
}

on aspx:

<asp:CheckBox runat="server" OnCheckedChanged="CheckAllChanged" AutoPostBack="true"  id="cb_selectall" />
<asp:HiddenField ID="HiddenCatID" runat="server" Value='<%# Eval("CatID") %>' />
<asp:HiddenField ID="HiddenDocID" runat="server" Value='<%# Eval("DocID") %>' />

You also need to EnableViewState=true on the DataList to maintain checkbox state and enable checking/unchecking.

---

Edit:

Because you have problems to get it running, here’s a complete working sample page.

Here are the required controls on aspx(note f.e. <tr runat="server" id="tr_category">):

<ItemTemplate>
    <table cellpadding="0" cellspacing="0" id="tbl_data">
        <tr runat="server" id="tr_category">
            <td>
                <asp:Label ID="lblHeader" runat="server" Font-Bold="True" Text='<%# Eval("categoryname") %>' Font-Underline="True"></asp:Label>
                <asp:Label runat="server" ID="lbl_cb_all">Select All
                <asp:CheckBox runat="server"  OnCheckedChanged="CheckAllChanged" AutoPostBack="true"  id="cb_selectall" />
                </asp:Label>
            </td>
        </tr>
        <tr runat="server" id="tr_data">
            <td>
                <asp:HiddenField ID="HiddenCatID" runat="server" Value='<%# Eval("CatID") %>' />
                <asp:CheckBox runat="server" id="cb_docid" />
                <asp:HyperLink ID="hpl_docfileencr" Text='<%# Eval("docfileencr") %>' NavigateUrl='<%# "~/PDFEncr/" + DataBinder.Eval(Container.DataItem, "docfileencr") %>'
                    Target="_blank" runat="server" />
                <br />
            </td>
        </tr>
    </table>
</ItemTemplate>

1. Ensure that the DataList is databound only if(!IsPostback), otherwise the checkbox selection will not be maintained:

   protected void Page_Load(object sender, EventArgs e)
   {
       if (!IsPostBack) BindDataList();
   }
   

2. I’m using ItemDataBound instead of PreRender which is important for the ViewState to be reloaded correctly. I’ve also simplified all:

   protected void DataList1_ItemDataBound(Object sender, DataListItemEventArgs e)
   {
       if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType==ListItemType.AlternatingItem)
       {
           var row  = (DataRowView)e.Item.DataItem;
           var view = row.DataView;
           var lastRow = e.Item.ItemIndex == 0 ? null : view[e.Item.ItemIndex-1];
           var tr_category = (System.Web.UI.HtmlControls.HtmlTableRow)e.Item.FindControl("tr_category");
           var sameCategory = lastRow != null && (int)row["catid"] == (int)lastRow["catid"];
           tr_category.Visible = !sameCategory;
       }
   }
   

3. The CheckAllChanged remains unchanged.

This works as expected even if you select a single document-checkbox and select a category-checkbox afterwards which causes a postback.