ajax with datalist giving error

Question

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I have a data list control which is placed inside a content place holder.

XML

<asp:Content ID="Content3" ContentPlaceHolderID="MainContent" runat="Server">
    <asp:ScriptManager ID="MainScriptManager" runat="server" />
    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <ContentTemplate>
            <asp:DataList ID="dlProdocut" runat="server" RepeatColumns="3" EditItemIndex="-1"
                RepeatDirection="Horizontal" OnItemDataBound="dlProdocut_ItemDataBound">
                <ItemTemplate>
                    <asp:Table ID="Table1" runat="server" border="0" CellSpacing="0" CellPadding="0">
                        <asp:TableRow>
                            <asp:TableCell Height="10" HorizontalAlign="Center" VerticalAlign="Top">

                            </asp:TableCell>
                        </asp:TableRow>
                        <%--Image--%>
                        <asp:TableRow>
                            <asp:TableCell Height="150" Width="7" HorizontalAlign="left" VerticalAlign="top">
                                <asp:HyperLink ID="hyrProductImg" runat="server">
                              <img alt='<%# DataBinder.Eval(Container.DataItem,"Title")%>' src="../images/<%# DataBinder.Eval(Container.DataItem,"SmallImage") %>" border="0" width="226" height="166" />
                                </asp:HyperLink>
                            </asp:TableCell>
                            <asp:TableCell Width="5">&nbsp;&nbsp;</asp:TableCell>
                        </asp:TableRow>
                        <%--Title--%>
                        <asp:TableRow>
                            <asp:TableCell Height="45" Width="7" CssClass="product-name" HorizontalAlign="Center"
                                VerticalAlign="Top">
                            <strong>&nbsp;<%# DataBinder.Eval(Container.DataItem, "Title")%></strong>
                            </asp:TableCell>
                        </asp:TableRow>
                        <%--ShortDescription--%>
                        <asp:TableRow>
                            <asp:TableCell Width="7" HorizontalAlign="Justify" VerticalAlign="Top" CssClass="testimonial-text">
                                <asp:Label ID="Label1" runat="server" Text='<%# DataBinder.Eval(Container.DataItem,"ShortDescription")%>'></asp:Label>
                            </asp:TableCell>
                        </asp:TableRow>
                        <%--Read More--%>
                        <asp:TableRow>
                            <asp:TableCell HorizontalAlign="Left">
                                <asp:HyperLink ID="lnkProductDetails" CssClass="read-more" runat="server">Read More &rarr;</asp:HyperLink>
                            </asp:TableCell>
                        </asp:TableRow>
                        <asp:TableRow>
                            <asp:TableCell Height="60" HorizontalAlign="Justify" VerticalAlign="Top" CssClass="testimonial-text">

                            </asp:TableCell>
                        </asp:TableRow>
                    </asp:Table>
                </ItemTemplate>
            </asp:DataList>
        </ContentTemplate>
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="dlProdocut" />
            <asp:AsyncPostBackTrigger ControlID="btnNext" />
        </Triggers>
    </asp:UpdatePanel>
    <asp:Label ID="lblPage" runat="server" Text="" />
    <asp:Button ID="btnPrevious" runat="server" Text="&lt;&lt;" />
    <asp:Button ID="btnNext" runat="server" Text="&gt;&gt;" OnClick="btnNext_Click" />
    <asp:Panel ID="BottomPager_Panel" runat="server">
    </asp:Panel>
</asp:Content>

On click of next button i am doing paging on the control and navigating to the next page.
On page load i am doing this

C#

if (!IsPostBack)
        {
            pageCount = 1;
            PageNo = 1;
            startPage = 6 * (PageNo - 1) + 1;
             lastPage = startPage + 5;
             bindDataList();
        }

This is my code for bindDataList

public void bindDataList()
    {
        
        string source = ConfigurationManager.ConnectionStrings["Cad-B"].ToString();
        SqlConnection con = new SqlConnection(source);
        SqlCommand cmd = new SqlCommand("sp_GetProductPagingByMenuId", con);
        //cmd.CommandType = CommandType.StoredProcedure;
        //cmd.CommandText = "sp_GetProductPagingByMenuId";
        con.Open();
        cmd.CommandType = CommandType.StoredProcedure;
        cmd.Parameters.Add("@startPage", startPage);
        cmd.Parameters.Add("@lastPage", lastPage);
        SqlDataReader dr =    cmd.ExecuteReader();
        DataTable dt = new DataTable();
        dt.Load(dr);
        
        dlProdocut.DataSource = dt;
        dlProdocut.DataBind();
    }

On click of next button i have written the following code

C#

protected void btnNext_Click(object sender, EventArgs e)
    {
        dlProdocut.DataSource = null;
        dlProdocut.DataBind();
        pageCount++;
        PageNo = pageCount;
        startPage = 6 * (PageNo - 1) + 1;
        lastPage = startPage + 5;
        bindDataList();
    }

Problem i am facing is that it every time shows me the same content that is loaded the first time on the page. When i debug the code i can see that the data list is loaded with the new records but it is not reflected on the page i tried removing caching but it dint help. The moment i removed the next button from the trigger section it is giving me the proper record but the complete page is getting post back which i dont want. This is the removed code

<asp:AsyncPostBackTrigger ControlID="btnNext" />

Please help i am stuck with this since long. I am new to this technology. Thanks in advance.

Posted 21-Jul-11 2:55am

ubaidh sayed

Updated 21-Jul-11 16:57pm

walterhevedeich

v2

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Comments

Christian Graus 21-Jul-11 19:30pm

why are people who are 'new to this technology;' trying to do complicated things, hoping it all magically works, in situations that sure look like paid work ?

2 solutions

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Al Moje · Answer 1 · 2011-07-21T19:26:00

Hi,
Your code you'd posted is incomplete.
Where did you initialized the value of the following:
1. pageCount
2. PageNo
3. startPage
4. lastPage
If I am not mistaken above variable was declared as public right?

If I am not mistaken your application has a Master Page.
If so, then clicking button(s) rather executing an event the system
will postback to Master Page then to present page, resulting the
value of you four above variable to initialized.

Think something to handle the above variables value not to initialized.

You may use.
Session State or View State to handle this situation...
Example:

Session["startPage"] = startPage.ToString();
or
VieState["startPage"] = startPage.ToString();

Then on retrieving from page event..

Example:
int startPage = Convert.ToInt(Session["startPage"])
or
int startPage = Convert.ToInt(ViewState["startPage"])

Session State Expires... Remember...

You may search the differences between the two usage and decide which is best...

Please remember to mark the replies as answers if they help and unmark them if they provide no help.

Regards,

Algem

Al Moje · Answer 2 · 2011-07-25T16:05:00

Solution 2

Hi,

Try to modified your code as:

<asp:UpdatePanel ID="UpdatePanel1" runat="server">

into

<asp:UpdatePanel ID="UpdatePanel1" runat="server" ChildrenAsTriggers="false" UpdateMod="Conditional">

then in your click event:

UpdatePanel1.Update();

or if not work the try this one:

<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<Triggers>
<asp:AsyncPostBackTrigger ControlID="btnNext" EventName="Click" />
&lt;asp:AsyncPostBackTrigger ControlID="dlProdocut" EventName="Click" /&gt;

 </Triggers>
 <ContentTemplate>

....
....

Hope this could help.

Regards,

Algem

Posted 25-Jul-11 16:05pm

Al Moje

Comments

ubaidh sayed 26-Jul-11 1:38am

Hi Al Moje,
Adding this part in code
<asp:AsyncPostBackTrigger ControlID="dlProdocut" EventName="Click"/> gives me an error.
"Could not find an event named 'Click' on associated control 'dlProdocut' for the trigger in UpdatePanel 'UpdatePanel1'."

Adding this
<asp:UpdatePanel ID="UpdatePanel1" runat="server" ChildrenAsTriggers="false" UpdateMod="Conditional">

is not working either.

Al Moje 26-Jul-11 2:29am

Hi,

I'd notice that the buttons:
<asp:Button ID="btnPrevious" runat="server" Text="<<" />
<asp:Button ID="btnNext" runat="server" Text=">>" OnClick="btnNext_Click" />

you were triggered is outside you update panel
try to place it inside you update panel...

ubaidh sayed 30-Jul-11 2:08am

I have tried that but nothing seems to work.
Here is my updated code.
<asp:Content ID="Content3" ContentPlaceHolderID="MainContent" runat="Server">
<asp:ScriptManager ID="MainScriptManager" runat="server" EnablePartialRendering="true" />
<asp:UpdatePanel ID="UpdatePanel1" runat="server" ChildrenAsTriggers="false" UpdateMode="Conditional">

<asp:DataList ID="dlProdocut" runat="server" RepeatColumns="3" RepeatDirection="Horizontal"
BorderColor="Black">

<asp:Table ID="Table1" runat="server" border="0" CellSpacing="0" CellPadding="0">
<asp:TableRow>
<asp:TableCell Height="10" HorizontalAlign="Center" VerticalAlign="Top">

<%--Image--%>
<asp:TableRow>
<asp:TableCell Height="150" Width="7" HorizontalAlign="left" VerticalAlign="top">
<asp:HyperLink ID="hyrProductImg" runat="server">
<img alt='<%# DataBinder.Eval(Container.DataItem,"Title")%>' src="../images/<%# DataBinder.Eval(Container.DataItem,"SmallImage") %>" border="0" width="226" height="166" />

<asp:TableCell Width="5">

<%--Title--%>
<asp:TableRow>
<asp:TableCell Height="45" Width="7" CssClass="product-name" HorizontalAlign="Center"
VerticalAlign="Top">
<%# DataBinder.Eval(Container.DataItem, "Title")%>

<%--ShortDescription--%>
<asp:TableRow>
<asp:TableCell Width="7" HorizontalAlign="Justify" VerticalAlign="Top" CssClass="testimonial-text">
<asp:Label ID="Label1" runat="server" Text='<%# DataBinder.Eval(Container.DataItem,"ShortDescription")%>'>

<%--Read More--%>
<asp:TableRow>
<asp:TableCell HorizontalAlign="Left">
<asp:HyperLink ID="lnkProductDetails" CssClass="read-more" runat="server">Read More →

<asp:TableRow>
<asp:TableCell Height="60" HorizontalAlign="Justify" VerticalAlign="Top" CssClass="testimonial-text">

<asp:Label ID="lblPage" runat="server" Text="" />
<asp:Button ID="Button1" runat="server" Text="<<" />
<asp:Button ID="btnNext" runat="server" Text=">>" OnClick="btnNext_Click" />

<Triggers>
<asp:AsyncPostBackTrigger ControlID="btnNext" EventName="Click" />
<asp:AsyncPostBackTrigger ControlID="dlProdocut" />
</Triggers>

<asp:Panel ID="BottomPager_Panel" runat="server">