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Why itemcommand event not fired on datalist?

Posted on 2009-04-08
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Last Modified: 2013-12-17
Hi,
I have a simple datalist that binds to a datatable. In the datalist, there is a button. It seems that i can't get this button to fire (when clicked) the itemcommand event on the datalist.

My intention is to use the button to get the item ID selected in the datalist.

Please help.

PS: I'd set the EnableEventValidation="False", as i got the error message when click on the button. See below.

Invalid postback or callback argument.  Event validation is enabled using <pages enableEventValidation="true"/> in configuration or <%@ Page EnableEventValidation="true" %> in a page.  
.aspx.vb
----------
Imports System.Data
 
Partial Class Default5
    Inherits System.Web.UI.Page
 
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
 
        'Nothing fancy, just populating the datalist with rows.
        Dim dt As New DataTable
        Dim dr As DataRow
        Dim dc As DataColumn
 
        dc = New DataColumn
        dc.ColumnName = "id"
        dt.Columns.Add(dc)
        dc = New DataColumn
        dc.ColumnName = "name"
        dt.Columns.Add(dc)
 
        dr = dt.NewRow
        dr("id") = 1
        dr("name") = "andy"
        dt.Rows.Add(dr)
 
        dr = dt.NewRow
        dr("id") = 2
        dr("name") = "ethan"
        dt.Rows.Add(dr)
 
        dr = dt.NewRow
        dr("id") = 3
        dr("name") = "Matt"
        dt.Rows.Add(dr)
 
        Datalist1.DataSource = dt
        Datalist1.DataBind()
 
    End Sub
 
    Protected Sub Datalist1_ItemCommand(ByVal source As Object, ByVal e As System.Web.UI.WebControls.DataListCommandEventArgs) Handles Datalist1.ItemCommand
       
 MsgBox("I'd clicked on the datalist button")  '# I"M NOT GETTING TO THIS EVENT ON BUTTON CLICK
 
    End Sub
 
End Class
 
 
.aspx
--------
<%@ Page EnableEventValidation="false" Language="VB" AutoEventWireup="false" CodeFile="Default5.aspx.vb" Inherits="Default5" %>
 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">
    <div>
 
    <asp:DataList ID="Datalist1" runat="server" 
            DataKeyField="id" 
            RepeatColumns = "3">
    <HeaderTemplate>
        <strong>Selection Table</strong>
    </HeaderTemplate>
    <ItemTemplate>
        ID: <%#DataBinder.Eval(Container.DataItem, "id")%>
        <br />
        Name: <%#DataBinder.Eval(Container.DataItem, "name")%>
        <br />
        <asp:Button runat="server" CommandName="getID" Text="Get ID" />
        <br /><br />
    </ItemTemplate>
    </asp:DataList>
    
    </div>
    </form>
</body>
</html>

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Question by:tangteng78
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3 Comments
 
LVL 37

Accepted Solution

by:
samtran0331 earned 2000 total points
ID: 24098672
try this:

aspx:
<asp:DataList ID="Datalist1" runat="server" DataKeyField="id" RepeatColumns="3">
<HeaderTemplate>
<strong>Selection Table</strong>
</HeaderTemplate>
<ItemTemplate>
ID:
<%#Eval("id")%>
<br />
Name:
<%#Eval("name")%>
<br />
<asp:Button ID="Button1" runat="server" CommandName="getID" CommandArgument='<%#Eval("id")%>'
Text="Get ID" />
<br />
<br />
</ItemTemplate>
</asp:DataList>


code:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
If Not Me.Page.IsPostBack = True Then
'Nothing fancy, just populating the datalist with rows.
Dim dt As New DataTable
Dim dr As DataRow
Dim dc As DataColumn

dc = New DataColumn
dc.ColumnName = "id"
dt.Columns.Add(dc)
dc = New DataColumn
dc.ColumnName = "name"
dt.Columns.Add(dc)

dr = dt.NewRow
dr("id") = 1
dr("name") = "andy"
dt.Rows.Add(dr)

dr = dt.NewRow
dr("id") = 2
dr("name") = "ethan"
dt.Rows.Add(dr)

dr = dt.NewRow
dr("id") = 3
dr("name") = "Matt"
dt.Rows.Add(dr)

Datalist1.DataSource = dt
Datalist1.DataBind()
End If

End Sub

Protected Sub Datalist1_ItemCommand(ByVal source As Object, ByVal e As System.Web.UI.WebControls.DataListCommandEventArgs) Handles Datalist1.ItemCommand
Select Case e.CommandName
Case "getID"
Me.Page.ClientScript.RegisterStartupScript(Me.GetType(), "msg", "alert('ID is: " & e.CommandArgument & "');", True)
End Select
End Sub
0
 
LVL 15

Expert Comment

by:NazoUK
ID: 24098721
You should't call databind on a postback as it will interfere with the event handlers.
0
 
LVL 37

Expert Comment

by:samtran0331
ID: 24098781
I posted a tested and working example...
0

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