How to use findcontrol in datalist !

Question

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In my following code-behind I want to assign the value to Label4 using datalist1. Earlier, in 'datalist1' I pass value to 'Label1' from column 'item_name'. On button18_click
I get the following exception as: 'Object reference not set to an instance of an object'.
Can anyone guide me in this regard so that I could pass the value to Label4 in code behind.
Does asp.net has this facility to findcontrol that lyes within a datalist?

XML

<asp:DataList ID="Datalist1" runat="server" DataKeyField="item_code"  RepeatDirection="Horizontal"
    RepeatLayout="Table"  OnItemCommand="dl_item_command"  >
    <HeaderTemplate>
    </HeaderTemplate>
    <ItemTemplate>
    Item Name:
    <asp:Label Id="Itmnamelbl" runat="server" Text='<%#Eval("item_name") %>'>
    </asp:Label>
    <br />
<asp:Button ID="Button18" runat="server" ForeColor="White"  onclick="Button18_Click"
 BackColor="Teal" Font-Size="small"
 style="z-index: 1;font-family:Sans-Serif; height:22px;  font-weight:900; "
 Text="Add to cart" />
 </ItemTemplate>
<SelectedItemTemplate>
<asp:Label id="Label1"
Text='<%#DataBinder.Eval(Container.DataItem,"item_name") %>'
runat="server"/>
<br />
</SelectedItemTemplate>
</asp:DataList>

C#

protected void Button18_Click(object sender, EventArgs e)
    {
              Label4.Text = (Datalist1.SelectedItem.FindControl("Label1").ToString());
    }

Posted 26-Sep-13 23:12pm

S.Rajendran from Coimbatore

Updated 27-Sep-13 18:11pm

Dholakiya Ankit

v4

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Comments

idenizeni 27-Sep-13 12:25pm

I'm guessing you never set the SelectedItem so this is the object that is throwing the error because it is not set to an instance.

2 solutions

Solution 1

You forgot convert object type as label.
Try this :

C#

Label4.Text = ((Label)DataList1.SelectedItem.FindControl("Label1")).Text;

--Amit

Posted 26-Sep-13 23:22pm

_Amy

Comments

S.Rajendran from Coimbatore 27-Sep-13 5:28am

I get the same exception.

S.Rajendran from Coimbatore 27-Sep-13 5:31am

i tried like this:
Label4.Text = ((Label)Datalist1.SelectedItem.FindControl("Label1")).Text;
Get the same exception.

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Harshil_Raval · Accepted Answer · 2013-09-27T18:48:00

Hi,

If you have set OnItemCommand event of datalist, then why you are firing alone button click event, which is inside datalist??
Add commandname,commandargument to button and handle button click event in OnItemCommand of datalist.

ASP.NET

<!--design side-->
<asp:datalist id="Datalist1" runat="server" datakeyfield="item_code" repeatdirection="Horizontal" repeatlayout="Table" onitemcommand="dl_item_command" xmlns:asp="#unknown">
    <headertemplate>
    </headertemplate>
    <itemtemplate>
         .....
         <!--See CommandName. Add CommandArgument if you required to do so.-->
         <asp:button id="Button18" runat="server" forecolor="White" commandname="myevent">
         BackColor="Teal" Font-Size="small" style="z-index: 1;font-family:Sans-Serif;
         height:22px;  font-weight:900;" Text="Add to cart" />
    </asp:button></itemtemplate>
</asp:datalist>

C#

//Server side
protected void dl_item_command(object source, DataListCommandEventArgs e)
{
    if (e.CommandName == "myevent") // check commandname here
    {
        int index = e.Item.ItemIndex;
        Label lbl = (Label)Datalist1.Items[index].FindControl("Label1");
        Label4.Text = lbl.Text; 
        // your code
    } 
}

Hope it helps you.
Thanks.